/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 4 -*- * vim: set ts=8 sts=4 et sw=4 tw=99: * This Source Code Form is subject to the terms of the Mozilla Public * License, v. 2.0. If a copy of the MPL was not distributed with this * file, You can obtain one at http://mozilla.org/MPL/2.0/. */ /* * This code implements an incremental mark-and-sweep garbage collector, with * most sweeping carried out in the background on a parallel thread. * * Full vs. zone GC * ---------------- * * The collector can collect all zones at once, or a subset. These types of * collection are referred to as a full GC and a zone GC respectively. * * The atoms zone is only collected in a full GC since objects in any zone may * have pointers to atoms, and these are not recorded in the cross compartment * pointer map. Also, the atoms zone is not collected if any thread has an * AutoKeepAtoms instance on the stack, or there are any exclusive threads using * the runtime. * * It is possible for an incremental collection that started out as a full GC to * become a zone GC if new zones are created during the course of the * collection. * * Incremental collection * ---------------------- * * For a collection to be carried out incrementally the following conditions * must be met: * - the collection must be run by calling js::GCSlice() rather than js::GC() * - the GC mode must have been set to JSGC_MODE_INCREMENTAL with * JS_SetGCParameter() * - no thread may have an AutoKeepAtoms instance on the stack * * The last condition is an engine-internal mechanism to ensure that incremental * collection is not carried out without the correct barriers being implemented. * For more information see 'Incremental marking' below. * * If the collection is not incremental, all foreground activity happens inside * a single call to GC() or GCSlice(). However the collection is not complete * until the background sweeping activity has finished. * * An incremental collection proceeds as a series of slices, interleaved with * mutator activity, i.e. running JavaScript code. Slices are limited by a time * budget. The slice finishes as soon as possible after the requested time has * passed. * * Collector states * ---------------- * * The collector proceeds through the following states, the current state being * held in JSRuntime::gcIncrementalState: * * - MarkRoots - marks the stack and other roots * - Mark - incrementally marks reachable things * - Sweep - sweeps zones in groups and continues marking unswept zones * - Finalize - performs background finalization, concurrent with mutator * - Compact - incrementally compacts by zone * - Decommit - performs background decommit and chunk removal * * The MarkRoots activity always takes place in the first slice. The next two * states can take place over one or more slices. * * In other words an incremental collection proceeds like this: * * Slice 1: MarkRoots: Roots pushed onto the mark stack. * Mark: The mark stack is processed by popping an element, * marking it, and pushing its children. * * ... JS code runs ... * * Slice 2: Mark: More mark stack processing. * * ... JS code runs ... * * Slice n-1: Mark: More mark stack processing. * * ... JS code runs ... * * Slice n: Mark: Mark stack is completely drained. * Sweep: Select first group of zones to sweep and sweep them. * * ... JS code runs ... * * Slice n+1: Sweep: Mark objects in unswept zones that were newly * identified as alive (see below). Then sweep more zone * groups. * * ... JS code runs ... * * Slice n+2: Sweep: Mark objects in unswept zones that were newly * identified as alive. Then sweep more zone groups. * * ... JS code runs ... * * Slice m: Sweep: Sweeping is finished, and background sweeping * started on the helper thread. * * ... JS code runs, remaining sweeping done on background thread ... * * When background sweeping finishes the GC is complete. * * Incremental marking * ------------------- * * Incremental collection requires close collaboration with the mutator (i.e., * JS code) to guarantee correctness. * * - During an incremental GC, if a memory location (except a root) is written * to, then the value it previously held must be marked. Write barriers * ensure this. * * - Any object that is allocated during incremental GC must start out marked. * * - Roots are marked in the first slice and hence don't need write barriers. * Roots are things like the C stack and the VM stack. * * The problem that write barriers solve is that between slices the mutator can * change the object graph. We must ensure that it cannot do this in such a way * that makes us fail to mark a reachable object (marking an unreachable object * is tolerable). * * We use a snapshot-at-the-beginning algorithm to do this. This means that we * promise to mark at least everything that is reachable at the beginning of * collection. To implement it we mark the old contents of every non-root memory * location written to by the mutator while the collection is in progress, using * write barriers. This is described in gc/Barrier.h. * * Incremental sweeping * -------------------- * * Sweeping is difficult to do incrementally because object finalizers must be * run at the start of sweeping, before any mutator code runs. The reason is * that some objects use their finalizers to remove themselves from caches. If * mutator code was allowed to run after the start of sweeping, it could observe * the state of the cache and create a new reference to an object that was just * about to be destroyed. * * Sweeping all finalizable objects in one go would introduce long pauses, so * instead sweeping broken up into groups of zones. Zones which are not yet * being swept are still marked, so the issue above does not apply. * * The order of sweeping is restricted by cross compartment pointers - for * example say that object |a| from zone A points to object |b| in zone B and * neither object was marked when we transitioned to the Sweep phase. Imagine we * sweep B first and then return to the mutator. It's possible that the mutator * could cause |a| to become alive through a read barrier (perhaps it was a * shape that was accessed via a shape table). Then we would need to mark |b|, * which |a| points to, but |b| has already been swept. * * So if there is such a pointer then marking of zone B must not finish before * marking of zone A. Pointers which form a cycle between zones therefore * restrict those zones to being swept at the same time, and these are found * using Tarjan's algorithm for finding the strongly connected components of a * graph. * * GC things without finalizers, and things with finalizers that are able to run * in the background, are swept on the background thread. This accounts for most * of the sweeping work. * * Reset * ----- * * During incremental collection it is possible, although unlikely, for * conditions to change such that incremental collection is no longer safe. In * this case, the collection is 'reset' by ResetIncrementalGC(). If we are in * the mark state, this just stops marking, but if we have started sweeping * already, we continue until we have swept the current zone group. Following a * reset, a new non-incremental collection is started. * * Compacting GC * ------------- * * Compacting GC happens at the end of a major GC as part of the last slice. * There are three parts: * * - Arenas are selected for compaction. * - The contents of those arenas are moved to new arenas. * - All references to moved things are updated. */ #include "jsgcinlines.h" #include "mozilla/ArrayUtils.h" #include "mozilla/DebugOnly.h" #include "mozilla/MacroForEach.h" #include "mozilla/MemoryReporting.h" #include "mozilla/Move.h" #include "mozilla/ScopeExit.h" #include <ctype.h> #include <string.h> #ifndef XP_WIN # include <sys/mman.h> # include <unistd.h> #endif #include "jsapi.h" #include "jsatom.h" #include "jscntxt.h" #include "jscompartment.h" #include "jsfriendapi.h" #include "jsobj.h" #include "jsprf.h" #include "jsscript.h" #include "jstypes.h" #include "jsutil.h" #include "jswatchpoint.h" #include "jsweakmap.h" #ifdef XP_WIN # include "jswin.h" #endif #include "gc/FindSCCs.h" #include "gc/GCInternals.h" #include "gc/GCTrace.h" #include "gc/Marking.h" #include "gc/Memory.h" #include "gc/Policy.h" #include "jit/BaselineJIT.h" #include "jit/IonCode.h" #include "jit/JitcodeMap.h" #include "js/SliceBudget.h" #include "proxy/DeadObjectProxy.h" #include "vm/Debugger.h" #include "vm/ProxyObject.h" #include "vm/Shape.h" #include "vm/SPSProfiler.h" #include "vm/String.h" #include "vm/Symbol.h" #include "vm/Time.h" #include "vm/TraceLogging.h" #include "vm/WrapperObject.h" #include "jsobjinlines.h" #include "jsscriptinlines.h" #include "vm/Stack-inl.h" #include "vm/String-inl.h" using namespace js; using namespace js::gc; using mozilla::ArrayLength; using mozilla::Get; using mozilla::HashCodeScrambler; using mozilla::Maybe; using mozilla::Swap; using JS::AutoGCRooter; /* Increase the IGC marking slice time if we are in highFrequencyGC mode. */ static const int IGC_MARK_SLICE_MULTIPLIER = 2; const AllocKind gc::slotsToThingKind[] = { /* 0 */ AllocKind::OBJECT0, AllocKind::OBJECT2, AllocKind::OBJECT2, AllocKind::OBJECT4, /* 4 */ AllocKind::OBJECT4, AllocKind::OBJECT8, AllocKind::OBJECT8, AllocKind::OBJECT8, /* 8 */ AllocKind::OBJECT8, AllocKind::OBJECT12, AllocKind::OBJECT12, AllocKind::OBJECT12, /* 12 */ AllocKind::OBJECT12, AllocKind::OBJECT16, AllocKind::OBJECT16, AllocKind::OBJECT16, /* 16 */ AllocKind::OBJECT16 }; static_assert(JS_ARRAY_LENGTH(slotsToThingKind) == SLOTS_TO_THING_KIND_LIMIT, "We have defined a slot count for each kind."); #define CHECK_THING_SIZE(allocKind, traceKind, type, sizedType) \ static_assert(sizeof(sizedType) >= SortedArenaList::MinThingSize, \ #sizedType " is smaller than SortedArenaList::MinThingSize!"); \ static_assert(sizeof(sizedType) >= sizeof(FreeSpan), \ #sizedType " is smaller than FreeSpan"); \ static_assert(sizeof(sizedType) % CellSize == 0, \ "Size of " #sizedType " is not a multiple of CellSize"); FOR_EACH_ALLOCKIND(CHECK_THING_SIZE); #undef CHECK_THING_SIZE const uint32_t Arena::ThingSizes[] = { #define EXPAND_THING_SIZE(allocKind, traceKind, type, sizedType) \ sizeof(sizedType), FOR_EACH_ALLOCKIND(EXPAND_THING_SIZE) #undef EXPAND_THING_SIZE }; FreeSpan ArenaLists::placeholder; #undef CHECK_THING_SIZE_INNER #undef CHECK_THING_SIZE #define OFFSET(type) uint32_t(ArenaHeaderSize + (ArenaSize - ArenaHeaderSize) % sizeof(type)) const uint32_t Arena::FirstThingOffsets[] = { #define EXPAND_FIRST_THING_OFFSET(allocKind, traceKind, type, sizedType) \ OFFSET(sizedType), FOR_EACH_ALLOCKIND(EXPAND_FIRST_THING_OFFSET) #undef EXPAND_FIRST_THING_OFFSET }; #undef OFFSET #define COUNT(type) uint32_t((ArenaSize - ArenaHeaderSize) / sizeof(type)) const uint32_t Arena::ThingsPerArena[] = { #define EXPAND_THINGS_PER_ARENA(allocKind, traceKind, type, sizedType) \ COUNT(sizedType), FOR_EACH_ALLOCKIND(EXPAND_THINGS_PER_ARENA) #undef EXPAND_THINGS_PER_ARENA }; #undef COUNT struct js::gc::FinalizePhase { gcstats::Phase statsPhase; AllocKinds kinds; }; /* * Finalization order for GC things swept incrementally on the main thrad. */ static const FinalizePhase IncrementalFinalizePhases[] = { { gcstats::PHASE_SWEEP_STRING, { AllocKind::EXTERNAL_STRING } }, { gcstats::PHASE_SWEEP_SCRIPT, { AllocKind::SCRIPT } }, { gcstats::PHASE_SWEEP_JITCODE, { AllocKind::JITCODE } } }; /* * Finalization order for GC things swept on the background thread. */ static const FinalizePhase BackgroundFinalizePhases[] = { { gcstats::PHASE_SWEEP_SCRIPT, { AllocKind::LAZY_SCRIPT } }, { gcstats::PHASE_SWEEP_OBJECT, { AllocKind::FUNCTION, AllocKind::FUNCTION_EXTENDED, AllocKind::OBJECT0_BACKGROUND, AllocKind::OBJECT2_BACKGROUND, AllocKind::OBJECT4_BACKGROUND, AllocKind::OBJECT8_BACKGROUND, AllocKind::OBJECT12_BACKGROUND, AllocKind::OBJECT16_BACKGROUND } }, { gcstats::PHASE_SWEEP_SCOPE, { AllocKind::SCOPE } }, { gcstats::PHASE_SWEEP_STRING, { AllocKind::FAT_INLINE_STRING, AllocKind::STRING, AllocKind::FAT_INLINE_ATOM, AllocKind::ATOM, AllocKind::SYMBOL } }, { gcstats::PHASE_SWEEP_SHAPE, { AllocKind::SHAPE, AllocKind::ACCESSOR_SHAPE, AllocKind::BASE_SHAPE, AllocKind::OBJECT_GROUP } } }; template<> JSObject* ArenaCellIterImpl::get<JSObject>() const { MOZ_ASSERT(!done()); return reinterpret_cast<JSObject*>(getCell()); } void Arena::unmarkAll() { uintptr_t* word = chunk()->bitmap.arenaBits(this); memset(word, 0, ArenaBitmapWords * sizeof(uintptr_t)); } /* static */ void Arena::staticAsserts() { static_assert(size_t(AllocKind::LIMIT) <= 255, "We must be able to fit the allockind into uint8_t."); static_assert(JS_ARRAY_LENGTH(ThingSizes) == size_t(AllocKind::LIMIT), "We haven't defined all thing sizes."); static_assert(JS_ARRAY_LENGTH(FirstThingOffsets) == size_t(AllocKind::LIMIT), "We haven't defined all offsets."); static_assert(JS_ARRAY_LENGTH(ThingsPerArena) == size_t(AllocKind::LIMIT), "We haven't defined all counts."); } template<typename T> inline size_t Arena::finalize(FreeOp* fop, AllocKind thingKind, size_t thingSize) { /* Enforce requirements on size of T. */ MOZ_ASSERT(thingSize % CellSize == 0); MOZ_ASSERT(thingSize <= 255); MOZ_ASSERT(allocated()); MOZ_ASSERT(thingKind == getAllocKind()); MOZ_ASSERT(thingSize == getThingSize()); MOZ_ASSERT(!hasDelayedMarking); MOZ_ASSERT(!markOverflow); MOZ_ASSERT(!allocatedDuringIncremental); uint_fast16_t firstThing = firstThingOffset(thingKind); uint_fast16_t firstThingOrSuccessorOfLastMarkedThing = firstThing; uint_fast16_t lastThing = ArenaSize - thingSize; FreeSpan newListHead; FreeSpan* newListTail = &newListHead; size_t nmarked = 0; if (MOZ_UNLIKELY(MemProfiler::enabled())) { for (ArenaCellIterUnderFinalize i(this); !i.done(); i.next()) { T* t = i.get<T>(); if (t->asTenured().isMarked()) MemProfiler::MarkTenured(reinterpret_cast<void*>(t)); } } for (ArenaCellIterUnderFinalize i(this); !i.done(); i.next()) { T* t = i.get<T>(); if (t->asTenured().isMarked()) { uint_fast16_t thing = uintptr_t(t) & ArenaMask; if (thing != firstThingOrSuccessorOfLastMarkedThing) { // We just finished passing over one or more free things, // so record a new FreeSpan. newListTail->initBounds(firstThingOrSuccessorOfLastMarkedThing, thing - thingSize, this); newListTail = newListTail->nextSpanUnchecked(this); } firstThingOrSuccessorOfLastMarkedThing = thing + thingSize; nmarked++; } else { t->finalize(fop); JS_POISON(t, JS_SWEPT_TENURED_PATTERN, thingSize); TraceTenuredFinalize(t); } } if (nmarked == 0) { // Do nothing. The caller will update the arena appropriately. MOZ_ASSERT(newListTail == &newListHead); JS_EXTRA_POISON(data, JS_SWEPT_TENURED_PATTERN, sizeof(data)); return nmarked; } MOZ_ASSERT(firstThingOrSuccessorOfLastMarkedThing != firstThing); uint_fast16_t lastMarkedThing = firstThingOrSuccessorOfLastMarkedThing - thingSize; if (lastThing == lastMarkedThing) { // If the last thing was marked, we will have already set the bounds of // the final span, and we just need to terminate the list. newListTail->initAsEmpty(); } else { // Otherwise, end the list with a span that covers the final stretch of free things. newListTail->initFinal(firstThingOrSuccessorOfLastMarkedThing, lastThing, this); } firstFreeSpan = newListHead; #ifdef DEBUG size_t nfree = numFreeThings(thingSize); MOZ_ASSERT(nfree + nmarked == thingsPerArena(thingKind)); #endif return nmarked; } // Finalize arenas from src list, releasing empty arenas if keepArenas wasn't // specified and inserting the others into the appropriate destination size // bins. template<typename T> static inline bool FinalizeTypedArenas(FreeOp* fop, Arena** src, SortedArenaList& dest, AllocKind thingKind, SliceBudget& budget, ArenaLists::KeepArenasEnum keepArenas) { // When operating in the foreground, take the lock at the top. Maybe<AutoLockGC> maybeLock; if (fop->onMainThread()) maybeLock.emplace(fop->runtime()); // During background sweeping free arenas are released later on in // sweepBackgroundThings(). MOZ_ASSERT_IF(!fop->onMainThread(), keepArenas == ArenaLists::KEEP_ARENAS); size_t thingSize = Arena::thingSize(thingKind); size_t thingsPerArena = Arena::thingsPerArena(thingKind); while (Arena* arena = *src) { *src = arena->next; size_t nmarked = arena->finalize<T>(fop, thingKind, thingSize); size_t nfree = thingsPerArena - nmarked; if (nmarked) dest.insertAt(arena, nfree); else if (keepArenas == ArenaLists::KEEP_ARENAS) arena->chunk()->recycleArena(arena, dest, thingsPerArena); else fop->runtime()->gc.releaseArena(arena, maybeLock.ref()); budget.step(thingsPerArena); if (budget.isOverBudget()) return false; } return true; } /* * Finalize the list. On return, |al|'s cursor points to the first non-empty * arena in the list (which may be null if all arenas are full). */ static bool FinalizeArenas(FreeOp* fop, Arena** src, SortedArenaList& dest, AllocKind thingKind, SliceBudget& budget, ArenaLists::KeepArenasEnum keepArenas) { switch (thingKind) { #define EXPAND_CASE(allocKind, traceKind, type, sizedType) \ case AllocKind::allocKind: \ return FinalizeTypedArenas<type>(fop, src, dest, thingKind, budget, keepArenas); FOR_EACH_ALLOCKIND(EXPAND_CASE) #undef EXPAND_CASE default: MOZ_CRASH("Invalid alloc kind"); } } Chunk* ChunkPool::pop() { MOZ_ASSERT(bool(head_) == bool(count_)); if (!count_) return nullptr; return remove(head_); } void ChunkPool::push(Chunk* chunk) { MOZ_ASSERT(!chunk->info.next); MOZ_ASSERT(!chunk->info.prev); chunk->info.next = head_; if (head_) head_->info.prev = chunk; head_ = chunk; ++count_; MOZ_ASSERT(verify()); } Chunk* ChunkPool::remove(Chunk* chunk) { MOZ_ASSERT(count_ > 0); MOZ_ASSERT(contains(chunk)); if (head_ == chunk) head_ = chunk->info.next; if (chunk->info.prev) chunk->info.prev->info.next = chunk->info.next; if (chunk->info.next) chunk->info.next->info.prev = chunk->info.prev; chunk->info.next = chunk->info.prev = nullptr; --count_; MOZ_ASSERT(verify()); return chunk; } #ifdef DEBUG bool ChunkPool::contains(Chunk* chunk) const { verify(); for (Chunk* cursor = head_; cursor; cursor = cursor->info.next) { if (cursor == chunk) return true; } return false; } bool ChunkPool::verify() const { MOZ_ASSERT(bool(head_) == bool(count_)); uint32_t count = 0; for (Chunk* cursor = head_; cursor; cursor = cursor->info.next, ++count) { MOZ_ASSERT_IF(cursor->info.prev, cursor->info.prev->info.next == cursor); MOZ_ASSERT_IF(cursor->info.next, cursor->info.next->info.prev == cursor); } MOZ_ASSERT(count_ == count); return true; } #endif void ChunkPool::Iter::next() { MOZ_ASSERT(!done()); current_ = current_->info.next; } ChunkPool GCRuntime::expireEmptyChunkPool(const AutoLockGC& lock) { MOZ_ASSERT(emptyChunks(lock).verify()); MOZ_ASSERT(tunables.minEmptyChunkCount(lock) <= tunables.maxEmptyChunkCount()); ChunkPool expired; while (emptyChunks(lock).count() > tunables.minEmptyChunkCount(lock)) { Chunk* chunk = emptyChunks(lock).pop(); prepareToFreeChunk(chunk->info); expired.push(chunk); } MOZ_ASSERT(expired.verify()); MOZ_ASSERT(emptyChunks(lock).verify()); MOZ_ASSERT(emptyChunks(lock).count() <= tunables.maxEmptyChunkCount()); MOZ_ASSERT(emptyChunks(lock).count() <= tunables.minEmptyChunkCount(lock)); return expired; } static void FreeChunkPool(JSRuntime* rt, ChunkPool& pool) { for (ChunkPool::Iter iter(pool); !iter.done();) { Chunk* chunk = iter.get(); iter.next(); pool.remove(chunk); MOZ_ASSERT(!chunk->info.numArenasFreeCommitted); UnmapPages(static_cast<void*>(chunk), ChunkSize); } MOZ_ASSERT(pool.count() == 0); } void GCRuntime::freeEmptyChunks(JSRuntime* rt, const AutoLockGC& lock) { FreeChunkPool(rt, emptyChunks(lock)); } inline void GCRuntime::prepareToFreeChunk(ChunkInfo& info) { MOZ_ASSERT(numArenasFreeCommitted >= info.numArenasFreeCommitted); numArenasFreeCommitted -= info.numArenasFreeCommitted; stats.count(gcstats::STAT_DESTROY_CHUNK); #ifdef DEBUG /* * Let FreeChunkPool detect a missing prepareToFreeChunk call before it * frees chunk. */ info.numArenasFreeCommitted = 0; #endif } inline void GCRuntime::updateOnArenaFree(const ChunkInfo& info) { ++numArenasFreeCommitted; } void Chunk::addArenaToFreeList(JSRuntime* rt, Arena* arena) { MOZ_ASSERT(!arena->allocated()); arena->next = info.freeArenasHead; info.freeArenasHead = arena; ++info.numArenasFreeCommitted; ++info.numArenasFree; rt->gc.updateOnArenaFree(info); } void Chunk::addArenaToDecommittedList(JSRuntime* rt, const Arena* arena) { ++info.numArenasFree; decommittedArenas.set(Chunk::arenaIndex(arena->address())); } void Chunk::recycleArena(Arena* arena, SortedArenaList& dest, size_t thingsPerArena) { arena->setAsFullyUnused(); dest.insertAt(arena, thingsPerArena); } void Chunk::releaseArena(JSRuntime* rt, Arena* arena, const AutoLockGC& lock) { MOZ_ASSERT(arena->allocated()); MOZ_ASSERT(!arena->hasDelayedMarking); arena->setAsNotAllocated(); addArenaToFreeList(rt, arena); updateChunkListAfterFree(rt, lock); } bool Chunk::decommitOneFreeArena(JSRuntime* rt, AutoLockGC& lock) { MOZ_ASSERT(info.numArenasFreeCommitted > 0); Arena* arena = fetchNextFreeArena(rt); updateChunkListAfterAlloc(rt, lock); bool ok; { AutoUnlockGC unlock(lock); ok = MarkPagesUnused(arena, ArenaSize); } if (ok) addArenaToDecommittedList(rt, arena); else addArenaToFreeList(rt, arena); updateChunkListAfterFree(rt, lock); return ok; } void Chunk::decommitAllArenasWithoutUnlocking(const AutoLockGC& lock) { for (size_t i = 0; i < ArenasPerChunk; ++i) { if (decommittedArenas.get(i) || arenas[i].allocated()) continue; if (MarkPagesUnused(&arenas[i], ArenaSize)) { info.numArenasFreeCommitted--; decommittedArenas.set(i); } } } void Chunk::updateChunkListAfterAlloc(JSRuntime* rt, const AutoLockGC& lock) { if (MOZ_UNLIKELY(!hasAvailableArenas())) { rt->gc.availableChunks(lock).remove(this); rt->gc.fullChunks(lock).push(this); } } void Chunk::updateChunkListAfterFree(JSRuntime* rt, const AutoLockGC& lock) { if (info.numArenasFree == 1) { rt->gc.fullChunks(lock).remove(this); rt->gc.availableChunks(lock).push(this); } else if (!unused()) { MOZ_ASSERT(!rt->gc.fullChunks(lock).contains(this)); MOZ_ASSERT(rt->gc.availableChunks(lock).contains(this)); MOZ_ASSERT(!rt->gc.emptyChunks(lock).contains(this)); } else { MOZ_ASSERT(unused()); rt->gc.availableChunks(lock).remove(this); decommitAllArenas(rt); MOZ_ASSERT(info.numArenasFreeCommitted == 0); rt->gc.recycleChunk(this, lock); } } void GCRuntime::releaseArena(Arena* arena, const AutoLockGC& lock) { arena->zone->usage.removeGCArena(); if (isBackgroundSweeping()) arena->zone->threshold.updateForRemovedArena(tunables); return arena->chunk()->releaseArena(rt, arena, lock); } GCRuntime::GCRuntime(JSRuntime* rt) : rt(rt), systemZone(nullptr), nursery(rt), storeBuffer(rt, nursery), stats(rt), marker(rt), usage(nullptr), mMemProfiler(rt), maxMallocBytes(0), nextCellUniqueId_(LargestTaggedNullCellPointer + 1), // Ensure disjoint from null tagged pointers. numArenasFreeCommitted(0), verifyPreData(nullptr), chunkAllocationSinceLastGC(false), lastGCTime(PRMJ_Now()), mode(JSGC_MODE_INCREMENTAL), numActiveZoneIters(0), cleanUpEverything(false), grayBufferState(GCRuntime::GrayBufferState::Unused), majorGCTriggerReason(JS::gcreason::NO_REASON), minorGCTriggerReason(JS::gcreason::NO_REASON), fullGCForAtomsRequested_(false), minorGCNumber(0), majorGCNumber(0), jitReleaseNumber(0), number(0), startNumber(0), isFull(false), #ifdef DEBUG disableStrictProxyCheckingCount(0), #endif incrementalState(gc::State::NotActive), lastMarkSlice(false), sweepOnBackgroundThread(false), blocksToFreeAfterSweeping(JSRuntime::TEMP_LIFO_ALLOC_PRIMARY_CHUNK_SIZE), blocksToFreeAfterMinorGC(JSRuntime::TEMP_LIFO_ALLOC_PRIMARY_CHUNK_SIZE), zoneGroupIndex(0), zoneGroups(nullptr), currentZoneGroup(nullptr), sweepZone(nullptr), sweepKind(AllocKind::FIRST), abortSweepAfterCurrentGroup(false), arenasAllocatedDuringSweep(nullptr), startedCompacting(false), relocatedArenasToRelease(nullptr), interFrameGC(false), defaultTimeBudget_(SliceBudget::UnlimitedTimeBudget), incrementalAllowed(true), generationalDisabled(0), compactingEnabled(true), compactingDisabledCount(0), manipulatingDeadZones(false), objectsMarkedInDeadZones(0), poked(false), fullCompartmentChecks(false), mallocBytesUntilGC(0), mallocGCTriggered(false), alwaysPreserveCode(false), inUnsafeRegion(0), #ifdef DEBUG noGCOrAllocationCheck(0), noNurseryAllocationCheck(0), arenasEmptyAtShutdown(true), #endif lock(mutexid::GCLock), allocTask(rt, emptyChunks_), decommitTask(rt), helperState(rt) { setGCMode(JSGC_MODE_GLOBAL); } /* * Lifetime in number of major GCs for type sets attached to scripts containing * observed types. */ static const uint64_t JIT_SCRIPT_RELEASE_TYPES_PERIOD = 20; bool GCRuntime::init(uint32_t maxbytes, uint32_t maxNurseryBytes) { InitMemorySubsystem(); if (!rootsHash.init(256)) return false; { AutoLockGC lock(rt); /* * Separate gcMaxMallocBytes from gcMaxBytes but initialize to maxbytes * for default backward API compatibility. */ MOZ_ALWAYS_TRUE(tunables.setParameter(JSGC_MAX_BYTES, maxbytes, lock)); setMaxMallocBytes(maxbytes); const char* size = getenv("JSGC_MARK_STACK_LIMIT"); if (size) setMarkStackLimit(atoi(size), lock); jitReleaseNumber = majorGCNumber + JIT_SCRIPT_RELEASE_TYPES_PERIOD; if (!nursery.init(maxNurseryBytes, lock)) return false; if (!nursery.isEnabled()) { MOZ_ASSERT(nursery.nurserySize() == 0); ++rt->gc.generationalDisabled; } else { MOZ_ASSERT(nursery.nurserySize() > 0); } } if (!InitTrace(*this)) return false; if (!marker.init(mode)) return false; return true; } void GCRuntime::finish() { /* Wait for the nursery sweeping to end. */ if (nursery.isEnabled()) nursery.waitBackgroundFreeEnd(); /* * Wait until the background finalization and allocation stops and the * helper thread shuts down before we forcefully release any remaining GC * memory. */ helperState.finish(); allocTask.cancel(GCParallelTask::CancelAndWait); decommitTask.cancel(GCParallelTask::CancelAndWait); /* Delete all remaining zones. */ if (rt->gcInitialized) { AutoSetThreadIsSweeping threadIsSweeping; for (ZonesIter zone(rt, WithAtoms); !zone.done(); zone.next()) { for (CompartmentsInZoneIter comp(zone); !comp.done(); comp.next()) js_delete(comp.get()); js_delete(zone.get()); } } zones.clear(); FreeChunkPool(rt, fullChunks_); FreeChunkPool(rt, availableChunks_); FreeChunkPool(rt, emptyChunks_); FinishTrace(); nursery.printTotalProfileTimes(); stats.printTotalProfileTimes(); } bool GCRuntime::setParameter(JSGCParamKey key, uint32_t value, AutoLockGC& lock) { switch (key) { case JSGC_MAX_MALLOC_BYTES: setMaxMallocBytes(value); for (ZonesIter zone(rt, WithAtoms); !zone.done(); zone.next()) zone->setGCMaxMallocBytes(maxMallocBytesAllocated() * 0.9); break; case JSGC_SLICE_TIME_BUDGET: defaultTimeBudget_ = value ? value : SliceBudget::UnlimitedTimeBudget; break; case JSGC_MARK_STACK_LIMIT: if (value == 0) return false; setMarkStackLimit(value, lock); break; case JSGC_MODE: if (mode != JSGC_MODE_GLOBAL && mode != JSGC_MODE_ZONE && mode != JSGC_MODE_INCREMENTAL) { return false; } mode = JSGCMode(value); break; case JSGC_COMPACTING_ENABLED: compactingEnabled = value != 0; break; default: if (!tunables.setParameter(key, value, lock)) return false; for (ZonesIter zone(rt, WithAtoms); !zone.done(); zone.next()) { zone->threshold.updateAfterGC(zone->usage.gcBytes(), GC_NORMAL, tunables, schedulingState, lock); } } return true; } bool GCSchedulingTunables::setParameter(JSGCParamKey key, uint32_t value, const AutoLockGC& lock) { // Limit heap growth factor to one hundred times size of current heap. const double MaxHeapGrowthFactor = 100; switch(key) { case JSGC_MAX_BYTES: gcMaxBytes_ = value; break; case JSGC_HIGH_FREQUENCY_TIME_LIMIT: highFrequencyThresholdUsec_ = value * PRMJ_USEC_PER_MSEC; break; case JSGC_HIGH_FREQUENCY_LOW_LIMIT: { uint64_t newLimit = (uint64_t)value * 1024 * 1024; if (newLimit == UINT64_MAX) return false; highFrequencyLowLimitBytes_ = newLimit; if (highFrequencyLowLimitBytes_ >= highFrequencyHighLimitBytes_) highFrequencyHighLimitBytes_ = highFrequencyLowLimitBytes_ + 1; MOZ_ASSERT(highFrequencyHighLimitBytes_ > highFrequencyLowLimitBytes_); break; } case JSGC_HIGH_FREQUENCY_HIGH_LIMIT: { uint64_t newLimit = (uint64_t)value * 1024 * 1024; if (newLimit == 0) return false; highFrequencyHighLimitBytes_ = newLimit; if (highFrequencyHighLimitBytes_ <= highFrequencyLowLimitBytes_) highFrequencyLowLimitBytes_ = highFrequencyHighLimitBytes_ - 1; MOZ_ASSERT(highFrequencyHighLimitBytes_ > highFrequencyLowLimitBytes_); break; } case JSGC_HIGH_FREQUENCY_HEAP_GROWTH_MAX: { double newGrowth = value / 100.0; if (newGrowth <= 0.85 || newGrowth > MaxHeapGrowthFactor) return false; highFrequencyHeapGrowthMax_ = newGrowth; MOZ_ASSERT(highFrequencyHeapGrowthMax_ / 0.85 > 1.0); break; } case JSGC_HIGH_FREQUENCY_HEAP_GROWTH_MIN: { double newGrowth = value / 100.0; if (newGrowth <= 0.85 || newGrowth > MaxHeapGrowthFactor) return false; highFrequencyHeapGrowthMin_ = newGrowth; MOZ_ASSERT(highFrequencyHeapGrowthMin_ / 0.85 > 1.0); break; } case JSGC_LOW_FREQUENCY_HEAP_GROWTH: { double newGrowth = value / 100.0; if (newGrowth <= 0.9 || newGrowth > MaxHeapGrowthFactor) return false; lowFrequencyHeapGrowth_ = newGrowth; MOZ_ASSERT(lowFrequencyHeapGrowth_ / 0.9 > 1.0); break; } case JSGC_DYNAMIC_HEAP_GROWTH: dynamicHeapGrowthEnabled_ = value != 0; break; case JSGC_DYNAMIC_MARK_SLICE: dynamicMarkSliceEnabled_ = value != 0; break; case JSGC_ALLOCATION_THRESHOLD: gcZoneAllocThresholdBase_ = value * 1024 * 1024; break; case JSGC_MIN_EMPTY_CHUNK_COUNT: minEmptyChunkCount_ = value; if (minEmptyChunkCount_ > maxEmptyChunkCount_) maxEmptyChunkCount_ = minEmptyChunkCount_; MOZ_ASSERT(maxEmptyChunkCount_ >= minEmptyChunkCount_); break; case JSGC_MAX_EMPTY_CHUNK_COUNT: maxEmptyChunkCount_ = value; if (minEmptyChunkCount_ > maxEmptyChunkCount_) minEmptyChunkCount_ = maxEmptyChunkCount_; MOZ_ASSERT(maxEmptyChunkCount_ >= minEmptyChunkCount_); break; case JSGC_REFRESH_FRAME_SLICES_ENABLED: refreshFrameSlicesEnabled_ = value != 0; break; default: MOZ_CRASH("Unknown GC parameter."); } return true; } uint32_t GCRuntime::getParameter(JSGCParamKey key, const AutoLockGC& lock) { switch (key) { case JSGC_MAX_BYTES: return uint32_t(tunables.gcMaxBytes()); case JSGC_MAX_MALLOC_BYTES: return maxMallocBytes; case JSGC_BYTES: return uint32_t(usage.gcBytes()); case JSGC_MODE: return uint32_t(mode); case JSGC_UNUSED_CHUNKS: return uint32_t(emptyChunks(lock).count()); case JSGC_TOTAL_CHUNKS: return uint32_t(fullChunks(lock).count() + availableChunks(lock).count() + emptyChunks(lock).count()); case JSGC_SLICE_TIME_BUDGET: if (defaultTimeBudget_ == SliceBudget::UnlimitedTimeBudget) { return 0; } else { MOZ_RELEASE_ASSERT(defaultTimeBudget_ >= 0); MOZ_RELEASE_ASSERT(defaultTimeBudget_ <= UINT32_MAX); return uint32_t(defaultTimeBudget_); } case JSGC_MARK_STACK_LIMIT: return marker.maxCapacity(); case JSGC_HIGH_FREQUENCY_TIME_LIMIT: return tunables.highFrequencyThresholdUsec() / PRMJ_USEC_PER_MSEC; case JSGC_HIGH_FREQUENCY_LOW_LIMIT: return tunables.highFrequencyLowLimitBytes() / 1024 / 1024; case JSGC_HIGH_FREQUENCY_HIGH_LIMIT: return tunables.highFrequencyHighLimitBytes() / 1024 / 1024; case JSGC_HIGH_FREQUENCY_HEAP_GROWTH_MAX: return uint32_t(tunables.highFrequencyHeapGrowthMax() * 100); case JSGC_HIGH_FREQUENCY_HEAP_GROWTH_MIN: return uint32_t(tunables.highFrequencyHeapGrowthMin() * 100); case JSGC_LOW_FREQUENCY_HEAP_GROWTH: return uint32_t(tunables.lowFrequencyHeapGrowth() * 100); case JSGC_DYNAMIC_HEAP_GROWTH: return tunables.isDynamicHeapGrowthEnabled(); case JSGC_DYNAMIC_MARK_SLICE: return tunables.isDynamicMarkSliceEnabled(); case JSGC_ALLOCATION_THRESHOLD: return tunables.gcZoneAllocThresholdBase() / 1024 / 1024; case JSGC_MIN_EMPTY_CHUNK_COUNT: return tunables.minEmptyChunkCount(lock); case JSGC_MAX_EMPTY_CHUNK_COUNT: return tunables.maxEmptyChunkCount(); case JSGC_COMPACTING_ENABLED: return compactingEnabled; case JSGC_REFRESH_FRAME_SLICES_ENABLED: return tunables.areRefreshFrameSlicesEnabled(); default: MOZ_ASSERT(key == JSGC_NUMBER); return uint32_t(number); } } void GCRuntime::setMarkStackLimit(size_t limit, AutoLockGC& lock) { MOZ_ASSERT(!rt->isHeapBusy()); AutoUnlockGC unlock(lock); marker.setMaxCapacity(limit); } bool GCRuntime::addBlackRootsTracer(JSTraceDataOp traceOp, void* data) { AssertHeapIsIdle(rt); return !!blackRootTracers.append(Callback<JSTraceDataOp>(traceOp, data)); } void GCRuntime::removeBlackRootsTracer(JSTraceDataOp traceOp, void* data) { // Can be called from finalizers for (size_t i = 0; i < blackRootTracers.length(); i++) { Callback<JSTraceDataOp>* e = &blackRootTracers[i]; if (e->op == traceOp && e->data == data) { blackRootTracers.erase(e); } } } void GCRuntime::setGrayRootsTracer(JSTraceDataOp traceOp, void* data) { AssertHeapIsIdle(rt); grayRootTracer.op = traceOp; grayRootTracer.data = data; } void GCRuntime::setGCCallback(JSGCCallback callback, void* data) { gcCallback.op = callback; gcCallback.data = data; } void GCRuntime::callGCCallback(JSGCStatus status) const { if (gcCallback.op) gcCallback.op(rt->contextFromMainThread(), status, gcCallback.data); } void GCRuntime::setObjectsTenuredCallback(JSObjectsTenuredCallback callback, void* data) { tenuredCallback.op = callback; tenuredCallback.data = data; } void GCRuntime::callObjectsTenuredCallback() { if (tenuredCallback.op) tenuredCallback.op(rt->contextFromMainThread(), tenuredCallback.data); } namespace { class AutoNotifyGCActivity { public: explicit AutoNotifyGCActivity(GCRuntime& gc) : gc_(gc) { if (!gc_.isIncrementalGCInProgress()) { gcstats::AutoPhase ap(gc_.stats, gcstats::PHASE_GC_BEGIN); gc_.callGCCallback(JSGC_BEGIN); } } ~AutoNotifyGCActivity() { if (!gc_.isIncrementalGCInProgress()) { gcstats::AutoPhase ap(gc_.stats, gcstats::PHASE_GC_END); gc_.callGCCallback(JSGC_END); } } private: GCRuntime& gc_; }; } // (anon) bool GCRuntime::addFinalizeCallback(JSFinalizeCallback callback, void* data) { return finalizeCallbacks.append(Callback<JSFinalizeCallback>(callback, data)); } void GCRuntime::removeFinalizeCallback(JSFinalizeCallback callback) { for (Callback<JSFinalizeCallback>* p = finalizeCallbacks.begin(); p < finalizeCallbacks.end(); p++) { if (p->op == callback) { finalizeCallbacks.erase(p); break; } } } void GCRuntime::callFinalizeCallbacks(FreeOp* fop, JSFinalizeStatus status) const { for (auto& p : finalizeCallbacks) p.op(fop, status, !isFull, p.data); } bool GCRuntime::addWeakPointerZoneGroupCallback(JSWeakPointerZoneGroupCallback callback, void* data) { return updateWeakPointerZoneGroupCallbacks.append( Callback<JSWeakPointerZoneGroupCallback>(callback, data)); } void GCRuntime::removeWeakPointerZoneGroupCallback(JSWeakPointerZoneGroupCallback callback) { for (auto& p : updateWeakPointerZoneGroupCallbacks) { if (p.op == callback) { updateWeakPointerZoneGroupCallbacks.erase(&p); break; } } } void GCRuntime::callWeakPointerZoneGroupCallbacks() const { for (auto const& p : updateWeakPointerZoneGroupCallbacks) p.op(rt->contextFromMainThread(), p.data); } bool GCRuntime::addWeakPointerCompartmentCallback(JSWeakPointerCompartmentCallback callback, void* data) { return updateWeakPointerCompartmentCallbacks.append( Callback<JSWeakPointerCompartmentCallback>(callback, data)); } void GCRuntime::removeWeakPointerCompartmentCallback(JSWeakPointerCompartmentCallback callback) { for (auto& p : updateWeakPointerCompartmentCallbacks) { if (p.op == callback) { updateWeakPointerCompartmentCallbacks.erase(&p); break; } } } void GCRuntime::callWeakPointerCompartmentCallbacks(JSCompartment* comp) const { for (auto const& p : updateWeakPointerCompartmentCallbacks) p.op(rt->contextFromMainThread(), comp, p.data); } JS::GCSliceCallback GCRuntime::setSliceCallback(JS::GCSliceCallback callback) { return stats.setSliceCallback(callback); } JS::GCNurseryCollectionCallback GCRuntime::setNurseryCollectionCallback(JS::GCNurseryCollectionCallback callback) { return stats.setNurseryCollectionCallback(callback); } JS::DoCycleCollectionCallback GCRuntime::setDoCycleCollectionCallback(JS::DoCycleCollectionCallback callback) { auto prior = gcDoCycleCollectionCallback; gcDoCycleCollectionCallback = Callback<JS::DoCycleCollectionCallback>(callback, nullptr); return prior.op; } void GCRuntime::callDoCycleCollectionCallback(JSContext* cx) { if (gcDoCycleCollectionCallback.op) gcDoCycleCollectionCallback.op(cx); } bool GCRuntime::addRoot(Value* vp, const char* name) { /* * Sometimes Firefox will hold weak references to objects and then convert * them to strong references by calling AddRoot (e.g., via PreserveWrapper, * or ModifyBusyCount in workers). We need a read barrier to cover these * cases. */ if (isIncrementalGCInProgress()) GCPtrValue::writeBarrierPre(*vp); return rootsHash.put(vp, name); } void GCRuntime::removeRoot(Value* vp) { rootsHash.remove(vp); poke(); } extern JS_FRIEND_API(bool) js::AddRawValueRoot(JSContext* cx, Value* vp, const char* name) { MOZ_ASSERT(vp); MOZ_ASSERT(name); bool ok = cx->runtime()->gc.addRoot(vp, name); if (!ok) JS_ReportOutOfMemory(cx); return ok; } extern JS_FRIEND_API(void) js::RemoveRawValueRoot(JSContext* cx, Value* vp) { cx->runtime()->gc.removeRoot(vp); } void GCRuntime::setMaxMallocBytes(size_t value) { /* * For compatibility treat any value that exceeds PTRDIFF_T_MAX to * mean that value. */ maxMallocBytes = (ptrdiff_t(value) >= 0) ? value : size_t(-1) >> 1; resetMallocBytes(); for (ZonesIter zone(rt, WithAtoms); !zone.done(); zone.next()) zone->setGCMaxMallocBytes(value); } void GCRuntime::resetMallocBytes() { mallocBytesUntilGC = ptrdiff_t(maxMallocBytes); mallocGCTriggered = false; } void GCRuntime::updateMallocCounter(JS::Zone* zone, size_t nbytes) { mallocBytesUntilGC -= ptrdiff_t(nbytes); if (MOZ_UNLIKELY(isTooMuchMalloc())) onTooMuchMalloc(); else if (zone) zone->updateMallocCounter(nbytes); } void GCRuntime::onTooMuchMalloc() { if (!mallocGCTriggered) mallocGCTriggered = triggerGC(JS::gcreason::TOO_MUCH_MALLOC); } double ZoneHeapThreshold::allocTrigger(bool highFrequencyGC) const { return (highFrequencyGC ? 0.85 : 0.9) * gcTriggerBytes(); } /* static */ double ZoneHeapThreshold::computeZoneHeapGrowthFactorForHeapSize(size_t lastBytes, const GCSchedulingTunables& tunables, const GCSchedulingState& state) { if (!tunables.isDynamicHeapGrowthEnabled()) return 3.0; // For small zones, our collection heuristics do not matter much: favor // something simple in this case. if (lastBytes < 1 * 1024 * 1024) return tunables.lowFrequencyHeapGrowth(); // If GC's are not triggering in rapid succession, use a lower threshold so // that we will collect garbage sooner. if (!state.inHighFrequencyGCMode()) return tunables.lowFrequencyHeapGrowth(); // The heap growth factor depends on the heap size after a GC and the GC // frequency. For low frequency GCs (more than 1sec between GCs) we let // the heap grow to 150%. For high frequency GCs we let the heap grow // depending on the heap size: // lastBytes < highFrequencyLowLimit: 300% // lastBytes > highFrequencyHighLimit: 150% // otherwise: linear interpolation between 300% and 150% based on lastBytes // Use shorter names to make the operation comprehensible. double minRatio = tunables.highFrequencyHeapGrowthMin(); double maxRatio = tunables.highFrequencyHeapGrowthMax(); double lowLimit = tunables.highFrequencyLowLimitBytes(); double highLimit = tunables.highFrequencyHighLimitBytes(); if (lastBytes <= lowLimit) return maxRatio; if (lastBytes >= highLimit) return minRatio; double factor = maxRatio - ((maxRatio - minRatio) * ((lastBytes - lowLimit) / (highLimit - lowLimit))); MOZ_ASSERT(factor >= minRatio); MOZ_ASSERT(factor <= maxRatio); return factor; } /* static */ size_t ZoneHeapThreshold::computeZoneTriggerBytes(double growthFactor, size_t lastBytes, JSGCInvocationKind gckind, const GCSchedulingTunables& tunables, const AutoLockGC& lock) { size_t base = gckind == GC_SHRINK ? Max(lastBytes, tunables.minEmptyChunkCount(lock) * ChunkSize) : Max(lastBytes, tunables.gcZoneAllocThresholdBase()); double trigger = double(base) * growthFactor; return size_t(Min(double(tunables.gcMaxBytes()), trigger)); } void ZoneHeapThreshold::updateAfterGC(size_t lastBytes, JSGCInvocationKind gckind, const GCSchedulingTunables& tunables, const GCSchedulingState& state, const AutoLockGC& lock) { gcHeapGrowthFactor_ = computeZoneHeapGrowthFactorForHeapSize(lastBytes, tunables, state); gcTriggerBytes_ = computeZoneTriggerBytes(gcHeapGrowthFactor_, lastBytes, gckind, tunables, lock); } void ZoneHeapThreshold::updateForRemovedArena(const GCSchedulingTunables& tunables) { size_t amount = ArenaSize * gcHeapGrowthFactor_; MOZ_ASSERT(amount > 0); if ((gcTriggerBytes_ < amount) || (gcTriggerBytes_ - amount < tunables.gcZoneAllocThresholdBase() * gcHeapGrowthFactor_)) { return; } gcTriggerBytes_ -= amount; } void GCMarker::delayMarkingArena(Arena* arena) { if (arena->hasDelayedMarking) { /* Arena already scheduled to be marked later */ return; } arena->setNextDelayedMarking(unmarkedArenaStackTop); unmarkedArenaStackTop = arena; #ifdef DEBUG markLaterArenas++; #endif } void GCMarker::delayMarkingChildren(const void* thing) { const TenuredCell* cell = TenuredCell::fromPointer(thing); cell->arena()->markOverflow = 1; delayMarkingArena(cell->arena()); } inline void ArenaLists::prepareForIncrementalGC() { purge(); for (auto i : AllAllocKinds()) { arenaLists[i].moveCursorToEnd(); } } /* Compacting GC */ bool GCRuntime::shouldCompact() { // Compact on shrinking GC if enabled, but skip compacting in incremental // GCs if we are currently animating. return invocationKind == GC_SHRINK && isCompactingGCEnabled() && (!isIncremental || rt->lastAnimationTime + PRMJ_USEC_PER_SEC < PRMJ_Now()); } void GCRuntime::disableCompactingGC() { MOZ_ASSERT(CurrentThreadCanAccessRuntime(rt)); ++compactingDisabledCount; } void GCRuntime::enableCompactingGC() { MOZ_ASSERT(CurrentThreadCanAccessRuntime(rt)); MOZ_ASSERT(compactingDisabledCount > 0); --compactingDisabledCount; } bool GCRuntime::isCompactingGCEnabled() const { MOZ_ASSERT(CurrentThreadCanAccessRuntime(rt)); return compactingEnabled && compactingDisabledCount == 0; } AutoDisableCompactingGC::AutoDisableCompactingGC(JSContext* cx) : gc(cx->gc) { gc.disableCompactingGC(); if (gc.isIncrementalGCInProgress() && gc.isCompactingGc()) FinishGC(cx); } AutoDisableCompactingGC::~AutoDisableCompactingGC() { gc.enableCompactingGC(); } static bool CanRelocateZone(Zone* zone) { return !zone->isAtomsZone() && !zone->isSelfHostingZone(); } static const AllocKind AllocKindsToRelocate[] = { AllocKind::FUNCTION, AllocKind::FUNCTION_EXTENDED, AllocKind::OBJECT0, AllocKind::OBJECT0_BACKGROUND, AllocKind::OBJECT2, AllocKind::OBJECT2_BACKGROUND, AllocKind::OBJECT4, AllocKind::OBJECT4_BACKGROUND, AllocKind::OBJECT8, AllocKind::OBJECT8_BACKGROUND, AllocKind::OBJECT12, AllocKind::OBJECT12_BACKGROUND, AllocKind::OBJECT16, AllocKind::OBJECT16_BACKGROUND, AllocKind::SCRIPT, AllocKind::LAZY_SCRIPT, AllocKind::SCOPE, AllocKind::SHAPE, AllocKind::ACCESSOR_SHAPE, AllocKind::BASE_SHAPE, AllocKind::FAT_INLINE_STRING, AllocKind::STRING, AllocKind::EXTERNAL_STRING, AllocKind::FAT_INLINE_ATOM, AllocKind::ATOM }; Arena* ArenaList::removeRemainingArenas(Arena** arenap) { // This is only ever called to remove arenas that are after the cursor, so // we don't need to update it. #ifdef DEBUG for (Arena* arena = *arenap; arena; arena = arena->next) MOZ_ASSERT(cursorp_ != &arena->next); #endif Arena* remainingArenas = *arenap; *arenap = nullptr; check(); return remainingArenas; } static bool ShouldRelocateAllArenas(JS::gcreason::Reason reason) { return reason == JS::gcreason::DEBUG_GC; } /* * Choose which arenas to relocate all cells from. Return an arena cursor that * can be passed to removeRemainingArenas(). */ Arena** ArenaList::pickArenasToRelocate(size_t& arenaTotalOut, size_t& relocTotalOut) { // Relocate the greatest number of arenas such that the number of used cells // in relocated arenas is less than or equal to the number of free cells in // unrelocated arenas. In other words we only relocate cells we can move // into existing arenas, and we choose the least full areans to relocate. // // This is made easier by the fact that the arena list has been sorted in // descending order of number of used cells, so we will always relocate a // tail of the arena list. All we need to do is find the point at which to // start relocating. check(); if (isCursorAtEnd()) return nullptr; Arena** arenap = cursorp_; // Next arena to consider for relocation. size_t previousFreeCells = 0; // Count of free cells before arenap. size_t followingUsedCells = 0; // Count of used cells after arenap. size_t fullArenaCount = 0; // Number of full arenas (not relocated). size_t nonFullArenaCount = 0; // Number of non-full arenas (considered for relocation). size_t arenaIndex = 0; // Index of the next arena to consider. for (Arena* arena = head_; arena != *cursorp_; arena = arena->next) fullArenaCount++; for (Arena* arena = *cursorp_; arena; arena = arena->next) { followingUsedCells += arena->countUsedCells(); nonFullArenaCount++; } mozilla::DebugOnly<size_t> lastFreeCells(0); size_t cellsPerArena = Arena::thingsPerArena((*arenap)->getAllocKind()); while (*arenap) { Arena* arena = *arenap; if (followingUsedCells <= previousFreeCells) break; size_t freeCells = arena->countFreeCells(); size_t usedCells = cellsPerArena - freeCells; followingUsedCells -= usedCells; #ifdef DEBUG MOZ_ASSERT(freeCells >= lastFreeCells); lastFreeCells = freeCells; #endif previousFreeCells += freeCells; arenap = &arena->next; arenaIndex++; } size_t relocCount = nonFullArenaCount - arenaIndex; MOZ_ASSERT(relocCount < nonFullArenaCount); MOZ_ASSERT((relocCount == 0) == (!*arenap)); arenaTotalOut += fullArenaCount + nonFullArenaCount; relocTotalOut += relocCount; return arenap; } #ifdef DEBUG inline bool PtrIsInRange(const void* ptr, const void* start, size_t length) { return uintptr_t(ptr) - uintptr_t(start) < length; } #endif static TenuredCell* AllocRelocatedCell(Zone* zone, AllocKind thingKind, size_t thingSize) { AutoEnterOOMUnsafeRegion oomUnsafe; void* dstAlloc = zone->arenas.allocateFromFreeList(thingKind, thingSize); if (!dstAlloc) dstAlloc = GCRuntime::refillFreeListInGC(zone, thingKind); if (!dstAlloc) { // This can only happen in zeal mode or debug builds as we don't // otherwise relocate more cells than we have existing free space // for. oomUnsafe.crash("Could not allocate new arena while compacting"); } return TenuredCell::fromPointer(dstAlloc); } static void RelocateCell(Zone* zone, TenuredCell* src, AllocKind thingKind, size_t thingSize) { JS::AutoSuppressGCAnalysis nogc(zone->contextFromMainThread()); // Allocate a new cell. MOZ_ASSERT(zone == src->zone()); TenuredCell* dst = AllocRelocatedCell(zone, thingKind, thingSize); // Copy source cell contents to destination. memcpy(dst, src, thingSize); // Move any uid attached to the object. src->zone()->transferUniqueId(dst, src); if (IsObjectAllocKind(thingKind)) { JSObject* srcObj = static_cast<JSObject*>(static_cast<Cell*>(src)); JSObject* dstObj = static_cast<JSObject*>(static_cast<Cell*>(dst)); if (srcObj->isNative()) { NativeObject* srcNative = &srcObj->as<NativeObject>(); NativeObject* dstNative = &dstObj->as<NativeObject>(); // Fixup the pointer to inline object elements if necessary. if (srcNative->hasFixedElements()) dstNative->setFixedElements(); // For copy-on-write objects that own their elements, fix up the // owner pointer to point to the relocated object. if (srcNative->denseElementsAreCopyOnWrite()) { GCPtrNativeObject& owner = dstNative->getElementsHeader()->ownerObject(); if (owner == srcNative) owner = dstNative; } } // Call object moved hook if present. if (JSObjectMovedOp op = srcObj->getClass()->extObjectMovedOp()) op(dstObj, srcObj); MOZ_ASSERT_IF(dstObj->isNative(), !PtrIsInRange((const Value*)dstObj->as<NativeObject>().getDenseElements(), src, thingSize)); } // Copy the mark bits. dst->copyMarkBitsFrom(src); // Mark source cell as forwarded and leave a pointer to the destination. RelocationOverlay* overlay = RelocationOverlay::fromCell(src); overlay->forwardTo(dst); } static void RelocateArena(Arena* arena, SliceBudget& sliceBudget) { MOZ_ASSERT(arena->allocated()); MOZ_ASSERT(!arena->hasDelayedMarking); MOZ_ASSERT(!arena->markOverflow); MOZ_ASSERT(!arena->allocatedDuringIncremental); MOZ_ASSERT(arena->bufferedCells->isEmpty()); Zone* zone = arena->zone; AllocKind thingKind = arena->getAllocKind(); size_t thingSize = arena->getThingSize(); for (ArenaCellIterUnderGC i(arena); !i.done(); i.next()) { RelocateCell(zone, i.getCell(), thingKind, thingSize); sliceBudget.step(); } #ifdef DEBUG for (ArenaCellIterUnderGC i(arena); !i.done(); i.next()) { TenuredCell* src = i.getCell(); MOZ_ASSERT(RelocationOverlay::isCellForwarded(src)); TenuredCell* dest = Forwarded(src); MOZ_ASSERT(src->isMarked(BLACK) == dest->isMarked(BLACK)); MOZ_ASSERT(src->isMarked(GRAY) == dest->isMarked(GRAY)); } #endif } static inline bool ShouldProtectRelocatedArenas(JS::gcreason::Reason reason) { // For zeal mode collections we don't release the relocated arenas // immediately. Instead we protect them and keep them around until the next // collection so we can catch any stray accesses to them. #ifdef DEBUG return reason == JS::gcreason::DEBUG_GC; #else return false; #endif } /* * Relocate all arenas identified by pickArenasToRelocate: for each arena, * relocate each cell within it, then add it to a list of relocated arenas. */ Arena* ArenaList::relocateArenas(Arena* toRelocate, Arena* relocated, SliceBudget& sliceBudget, gcstats::Statistics& stats) { check(); while (Arena* arena = toRelocate) { toRelocate = arena->next; RelocateArena(arena, sliceBudget); // Prepend to list of relocated arenas arena->next = relocated; relocated = arena; stats.count(gcstats::STAT_ARENA_RELOCATED); } check(); return relocated; } // Skip compacting zones unless we can free a certain proportion of their GC // heap memory. static const double MIN_ZONE_RECLAIM_PERCENT = 2.0; static bool ShouldRelocateZone(size_t arenaCount, size_t relocCount, JS::gcreason::Reason reason) { if (relocCount == 0) return false; if (IsOOMReason(reason)) return true; return (relocCount * 100.0) / arenaCount >= MIN_ZONE_RECLAIM_PERCENT; } bool ArenaLists::relocateArenas(Zone* zone, Arena*& relocatedListOut, JS::gcreason::Reason reason, SliceBudget& sliceBudget, gcstats::Statistics& stats) { // This is only called from the main thread while we are doing a GC, so // there is no need to lock. MOZ_ASSERT(CurrentThreadCanAccessRuntime(runtime_)); MOZ_ASSERT(runtime_->gc.isHeapCompacting()); MOZ_ASSERT(!runtime_->gc.isBackgroundSweeping()); // Clear all the free lists. purge(); if (ShouldRelocateAllArenas(reason)) { zone->prepareForCompacting(); for (auto kind : AllocKindsToRelocate) { ArenaList& al = arenaLists[kind]; Arena* allArenas = al.head(); al.clear(); relocatedListOut = al.relocateArenas(allArenas, relocatedListOut, sliceBudget, stats); } } else { size_t arenaCount = 0; size_t relocCount = 0; AllAllocKindArray<Arena**> toRelocate; for (auto kind : AllocKindsToRelocate) toRelocate[kind] = arenaLists[kind].pickArenasToRelocate(arenaCount, relocCount); if (!ShouldRelocateZone(arenaCount, relocCount, reason)) return false; zone->prepareForCompacting(); for (auto kind : AllocKindsToRelocate) { if (toRelocate[kind]) { ArenaList& al = arenaLists[kind]; Arena* arenas = al.removeRemainingArenas(toRelocate[kind]); relocatedListOut = al.relocateArenas(arenas, relocatedListOut, sliceBudget, stats); } } } return true; } bool GCRuntime::relocateArenas(Zone* zone, JS::gcreason::Reason reason, Arena*& relocatedListOut, SliceBudget& sliceBudget) { gcstats::AutoPhase ap(stats, gcstats::PHASE_COMPACT_MOVE); MOZ_ASSERT(!zone->isPreservingCode()); MOZ_ASSERT(CanRelocateZone(zone)); js::CancelOffThreadIonCompile(rt, JS::Zone::Compact); if (!zone->arenas.relocateArenas(zone, relocatedListOut, reason, sliceBudget, stats)) return false; #ifdef DEBUG // Check that we did as much compaction as we should have. There // should always be less than one arena's worth of free cells. for (auto i : AllocKindsToRelocate) { ArenaList& al = zone->arenas.arenaLists[i]; size_t freeCells = 0; for (Arena* arena = al.arenaAfterCursor(); arena; arena = arena->next) freeCells += arena->countFreeCells(); MOZ_ASSERT(freeCells < Arena::thingsPerArena(i)); } #endif return true; } void MovingTracer::onObjectEdge(JSObject** objp) { JSObject* obj = *objp; if (obj->runtimeFromAnyThread() == runtime() && IsForwarded(obj)) *objp = Forwarded(obj); } void MovingTracer::onShapeEdge(Shape** shapep) { Shape* shape = *shapep; if (shape->runtimeFromAnyThread() == runtime() && IsForwarded(shape)) *shapep = Forwarded(shape); } void MovingTracer::onStringEdge(JSString** stringp) { JSString* string = *stringp; if (string->runtimeFromAnyThread() == runtime() && IsForwarded(string)) *stringp = Forwarded(string); } void MovingTracer::onScriptEdge(JSScript** scriptp) { JSScript* script = *scriptp; if (script->runtimeFromAnyThread() == runtime() && IsForwarded(script)) *scriptp = Forwarded(script); } void MovingTracer::onLazyScriptEdge(LazyScript** lazyp) { LazyScript* lazy = *lazyp; if (lazy->runtimeFromAnyThread() == runtime() && IsForwarded(lazy)) *lazyp = Forwarded(lazy); } void MovingTracer::onBaseShapeEdge(BaseShape** basep) { BaseShape* base = *basep; if (base->runtimeFromAnyThread() == runtime() && IsForwarded(base)) *basep = Forwarded(base); } void MovingTracer::onScopeEdge(Scope** scopep) { Scope* scope = *scopep; if (scope->runtimeFromAnyThread() == runtime() && IsForwarded(scope)) *scopep = Forwarded(scope); } void Zone::prepareForCompacting() { FreeOp* fop = runtimeFromMainThread()->defaultFreeOp(); discardJitCode(fop); } void GCRuntime::sweepTypesAfterCompacting(Zone* zone) { FreeOp* fop = rt->defaultFreeOp(); zone->beginSweepTypes(fop, rt->gc.releaseObservedTypes && !zone->isPreservingCode()); AutoClearTypeInferenceStateOnOOM oom(zone); for (auto script = zone->cellIter<JSScript>(); !script.done(); script.next()) script->maybeSweepTypes(&oom); for (auto group = zone->cellIter<ObjectGroup>(); !group.done(); group.next()) group->maybeSweep(&oom); zone->types.endSweep(rt); } void GCRuntime::sweepZoneAfterCompacting(Zone* zone) { MOZ_ASSERT(zone->isCollecting()); FreeOp* fop = rt->defaultFreeOp(); sweepTypesAfterCompacting(zone); zone->sweepBreakpoints(fop); zone->sweepWeakMaps(); for (auto* cache : zone->weakCaches_) cache->sweep(); for (CompartmentsInZoneIter c(zone); !c.done(); c.next()) { c->objectGroups.sweep(fop); c->sweepRegExps(); c->sweepSavedStacks(); c->sweepGlobalObject(fop); c->sweepSelfHostingScriptSource(); c->sweepDebugEnvironments(); c->sweepJitCompartment(fop); c->sweepNativeIterators(); c->sweepTemplateObjects(); } } template <typename T> static inline void UpdateCellPointers(MovingTracer* trc, T* cell) { cell->fixupAfterMovingGC(); cell->traceChildren(trc); } template <typename T> static void UpdateArenaPointersTyped(MovingTracer* trc, Arena* arena, JS::TraceKind traceKind) { for (ArenaCellIterUnderGC i(arena); !i.done(); i.next()) UpdateCellPointers(trc, reinterpret_cast<T*>(i.getCell())); } /* * Update the internal pointers for all cells in an arena. */ static void UpdateArenaPointers(MovingTracer* trc, Arena* arena) { AllocKind kind = arena->getAllocKind(); switch (kind) { #define EXPAND_CASE(allocKind, traceKind, type, sizedType) \ case AllocKind::allocKind: \ UpdateArenaPointersTyped<type>(trc, arena, JS::TraceKind::traceKind); \ return; FOR_EACH_ALLOCKIND(EXPAND_CASE) #undef EXPAND_CASE default: MOZ_CRASH("Invalid alloc kind for UpdateArenaPointers"); } } namespace js { namespace gc { struct ArenaListSegment { Arena* begin; Arena* end; }; struct ArenasToUpdate { ArenasToUpdate(Zone* zone, AllocKinds kinds); bool done() { return kind == AllocKind::LIMIT; } ArenaListSegment getArenasToUpdate(AutoLockHelperThreadState& lock, unsigned maxLength); private: AllocKinds kinds; // Selects which thing kinds to update Zone* zone; // Zone to process AllocKind kind; // Current alloc kind to process Arena* arena; // Next arena to process AllocKind nextAllocKind(AllocKind i) { return AllocKind(uint8_t(i) + 1); } bool shouldProcessKind(AllocKind kind); Arena* next(AutoLockHelperThreadState& lock); }; ArenasToUpdate::ArenasToUpdate(Zone* zone, AllocKinds kinds) : kinds(kinds), zone(zone), kind(AllocKind::FIRST), arena(nullptr) { MOZ_ASSERT(zone->isGCCompacting()); } Arena* ArenasToUpdate::next(AutoLockHelperThreadState& lock) { // Find the next arena to update. // // This iterates through the GC thing kinds filtered by shouldProcessKind(), // and then through thea arenas of that kind. All state is held in the // object and we just return when we find an arena. for (; kind < AllocKind::LIMIT; kind = nextAllocKind(kind)) { if (kinds.contains(kind)) { if (!arena) arena = zone->arenas.getFirstArena(kind); else arena = arena->next; if (arena) return arena; } } MOZ_ASSERT(!arena); MOZ_ASSERT(done()); return nullptr; } ArenaListSegment ArenasToUpdate::getArenasToUpdate(AutoLockHelperThreadState& lock, unsigned maxLength) { Arena* begin = next(lock); if (!begin) return { nullptr, nullptr }; Arena* last = begin; unsigned count = 1; while (last->next && count < maxLength) { last = last->next; count++; } arena = last; return { begin, last->next }; } struct UpdatePointersTask : public GCParallelTaskHelper<UpdatePointersTask> { // Maximum number of arenas to update in one block. #ifdef DEBUG static const unsigned MaxArenasToProcess = 16; #else static const unsigned MaxArenasToProcess = 256; #endif UpdatePointersTask(JSRuntime* rt, ArenasToUpdate* source, AutoLockHelperThreadState& lock) : rt_(rt), source_(source) { arenas_.begin = nullptr; arenas_.end = nullptr; } void run(); private: JSRuntime* rt_; ArenasToUpdate* source_; ArenaListSegment arenas_; bool getArenasToUpdate(); void updateArenas(); }; bool UpdatePointersTask::getArenasToUpdate() { AutoLockHelperThreadState lock; arenas_ = source_->getArenasToUpdate(lock, MaxArenasToProcess); return arenas_.begin != nullptr; } void UpdatePointersTask::updateArenas() { MovingTracer trc(rt_); for (Arena* arena = arenas_.begin; arena != arenas_.end; arena = arena->next) UpdateArenaPointers(&trc, arena); } /* virtual */ void UpdatePointersTask::run() { while (getArenasToUpdate()) updateArenas(); } } // namespace gc } // namespace js static const size_t MinCellUpdateBackgroundTasks = 2; static const size_t MaxCellUpdateBackgroundTasks = 8; static size_t CellUpdateBackgroundTaskCount() { if (!CanUseExtraThreads()) return 0; size_t targetTaskCount = HelperThreadState().cpuCount / 2; return Min(Max(targetTaskCount, MinCellUpdateBackgroundTasks), MaxCellUpdateBackgroundTasks); } static bool CanUpdateKindInBackground(AllocKind kind) { // We try to update as many GC things in parallel as we can, but there are // kinds for which this might not be safe: // - we assume JSObjects that are foreground finalized are not safe to // update in parallel // - updating a shape touches child shapes in fixupShapeTreeAfterMovingGC() if (!js::gc::IsBackgroundFinalized(kind) || IsShapeAllocKind(kind)) return false; return true; } static AllocKinds ForegroundUpdateKinds(AllocKinds kinds) { AllocKinds result; for (AllocKind kind : kinds) { if (!CanUpdateKindInBackground(kind)) result += kind; } return result; } void GCRuntime::updateTypeDescrObjects(MovingTracer* trc, Zone* zone) { zone->typeDescrObjects.sweep(); for (auto r = zone->typeDescrObjects.all(); !r.empty(); r.popFront()) UpdateCellPointers(trc, r.front()); } void GCRuntime::updateCellPointers(MovingTracer* trc, Zone* zone, AllocKinds kinds, size_t bgTaskCount) { AllocKinds fgKinds = bgTaskCount == 0 ? kinds : ForegroundUpdateKinds(kinds); AllocKinds bgKinds = kinds - fgKinds; ArenasToUpdate fgArenas(zone, fgKinds); ArenasToUpdate bgArenas(zone, bgKinds); Maybe<UpdatePointersTask> fgTask; Maybe<UpdatePointersTask> bgTasks[MaxCellUpdateBackgroundTasks]; size_t tasksStarted = 0; { AutoLockHelperThreadState lock; fgTask.emplace(rt, &fgArenas, lock); for (size_t i = 0; i < bgTaskCount && !bgArenas.done(); i++) { bgTasks[i].emplace(rt, &bgArenas, lock); startTask(*bgTasks[i], gcstats::PHASE_COMPACT_UPDATE_CELLS, lock); tasksStarted++; } } fgTask->runFromMainThread(rt); { AutoLockHelperThreadState lock; for (size_t i = 0; i < tasksStarted; i++) joinTask(*bgTasks[i], gcstats::PHASE_COMPACT_UPDATE_CELLS, lock); } } // After cells have been relocated any pointers to a cell's old locations must // be updated to point to the new location. This happens by iterating through // all cells in heap and tracing their children (non-recursively) to update // them. // // This is complicated by the fact that updating a GC thing sometimes depends on // making use of other GC things. After a moving GC these things may not be in // a valid state since they may contain pointers which have not been updated // yet. // // The main dependencies are: // // - Updating a JSObject makes use of its shape // - Updating a typed object makes use of its type descriptor object // // This means we require at least three phases for update: // // 1) shapes // 2) typed object type descriptor objects // 3) all other objects // // Also, there can be data races calling IsForwarded() on the new location of a // cell that is being updated in parallel on another thread. This can be avoided // by updating some kinds of cells in different phases. This is done for JSScripts // and LazyScripts, and JSScripts and Scopes. // // Since we want to minimize the number of phases, we put everything else into // the first phase and label it the 'misc' phase. static const AllocKinds UpdatePhaseMisc { AllocKind::SCRIPT, AllocKind::BASE_SHAPE, AllocKind::SHAPE, AllocKind::ACCESSOR_SHAPE, AllocKind::OBJECT_GROUP, AllocKind::STRING, AllocKind::JITCODE }; static const AllocKinds UpdatePhaseObjects { AllocKind::LAZY_SCRIPT, AllocKind::SCOPE, AllocKind::FUNCTION, AllocKind::FUNCTION_EXTENDED, AllocKind::OBJECT0, AllocKind::OBJECT0_BACKGROUND, AllocKind::OBJECT2, AllocKind::OBJECT2_BACKGROUND, AllocKind::OBJECT4, AllocKind::OBJECT4_BACKGROUND, AllocKind::OBJECT8, AllocKind::OBJECT8_BACKGROUND, AllocKind::OBJECT12, AllocKind::OBJECT12_BACKGROUND, AllocKind::OBJECT16, AllocKind::OBJECT16_BACKGROUND }; void GCRuntime::updateAllCellPointers(MovingTracer* trc, Zone* zone) { AutoDisableProxyCheck noProxyCheck(rt); // These checks assert when run in parallel. size_t bgTaskCount = CellUpdateBackgroundTaskCount(); updateCellPointers(trc, zone, UpdatePhaseMisc, bgTaskCount); // Update TypeDescrs before all other objects as typed objects access these // objects when we trace them. updateTypeDescrObjects(trc, zone); updateCellPointers(trc, zone, UpdatePhaseObjects, bgTaskCount); } /* * Update pointers to relocated cells by doing a full heap traversal and sweep. * * The latter is necessary to update weak references which are not marked as * part of the traversal. */ void GCRuntime::updatePointersToRelocatedCells(Zone* zone, AutoLockForExclusiveAccess& lock) { MOZ_ASSERT(!rt->isBeingDestroyed()); MOZ_ASSERT(zone->isGCCompacting()); gcstats::AutoPhase ap(stats, gcstats::PHASE_COMPACT_UPDATE); MovingTracer trc(rt); zone->fixupAfterMovingGC(); // Fixup compartment global pointers as these get accessed during marking. for (CompartmentsInZoneIter comp(zone); !comp.done(); comp.next()) comp->fixupAfterMovingGC(); JSCompartment::fixupCrossCompartmentWrappersAfterMovingGC(&trc); rt->spsProfiler.fixupStringsMapAfterMovingGC(); // Iterate through all cells that can contain relocatable pointers to update // them. Since updating each cell is independent we try to parallelize this // as much as possible. updateAllCellPointers(&trc, zone); // Mark roots to update them. { traceRuntimeForMajorGC(&trc, lock); gcstats::AutoPhase ap(stats, gcstats::PHASE_MARK_ROOTS); Debugger::markAll(&trc); Debugger::markIncomingCrossCompartmentEdges(&trc); WeakMapBase::markAll(zone, &trc); for (CompartmentsInZoneIter c(zone); !c.done(); c.next()) { c->trace(&trc); if (c->watchpointMap) c->watchpointMap->markAll(&trc); } // Mark all gray roots, making sure we call the trace callback to get the // current set. if (JSTraceDataOp op = grayRootTracer.op) (*op)(&trc, grayRootTracer.data); } // Sweep everything to fix up weak pointers WatchpointMap::sweepAll(rt); Debugger::sweepAll(rt->defaultFreeOp()); jit::JitRuntime::SweepJitcodeGlobalTable(rt); rt->gc.sweepZoneAfterCompacting(zone); // Type inference may put more blocks here to free. blocksToFreeAfterSweeping.freeAll(); // Call callbacks to get the rest of the system to fixup other untraced pointers. callWeakPointerZoneGroupCallbacks(); for (CompartmentsInZoneIter comp(zone); !comp.done(); comp.next()) callWeakPointerCompartmentCallbacks(comp); if (rt->sweepZoneCallback) rt->sweepZoneCallback(zone); } void GCRuntime::protectAndHoldArenas(Arena* arenaList) { for (Arena* arena = arenaList; arena; ) { MOZ_ASSERT(arena->allocated()); Arena* next = arena->next; if (!next) { // Prepend to hold list before we protect the memory. arena->next = relocatedArenasToRelease; relocatedArenasToRelease = arenaList; } ProtectPages(arena, ArenaSize); arena = next; } } void GCRuntime::unprotectHeldRelocatedArenas() { for (Arena* arena = relocatedArenasToRelease; arena; arena = arena->next) { UnprotectPages(arena, ArenaSize); MOZ_ASSERT(arena->allocated()); } } void GCRuntime::releaseRelocatedArenas(Arena* arenaList) { AutoLockGC lock(rt); releaseRelocatedArenasWithoutUnlocking(arenaList, lock); } void GCRuntime::releaseRelocatedArenasWithoutUnlocking(Arena* arenaList, const AutoLockGC& lock) { // Release the relocated arenas, now containing only forwarding pointers unsigned count = 0; while (arenaList) { Arena* arena = arenaList; arenaList = arenaList->next; // Clear the mark bits arena->unmarkAll(); // Mark arena as empty arena->setAsFullyUnused(); #if defined(JS_CRASH_DIAGNOSTICS) JS_POISON(reinterpret_cast<void*>(arena->thingsStart()), JS_MOVED_TENURED_PATTERN, arena->getThingsSpan()); #endif releaseArena(arena, lock); ++count; } } // In debug mode we don't always release relocated arenas straight away. // Sometimes protect them instead and hold onto them until the next GC sweep // phase to catch any pointers to them that didn't get forwarded. void GCRuntime::releaseHeldRelocatedArenas() { #ifdef DEBUG unprotectHeldRelocatedArenas(); Arena* arenas = relocatedArenasToRelease; relocatedArenasToRelease = nullptr; releaseRelocatedArenas(arenas); #endif } void GCRuntime::releaseHeldRelocatedArenasWithoutUnlocking(const AutoLockGC& lock) { #ifdef DEBUG unprotectHeldRelocatedArenas(); releaseRelocatedArenasWithoutUnlocking(relocatedArenasToRelease, lock); relocatedArenasToRelease = nullptr; #endif } void ReleaseArenaList(JSRuntime* rt, Arena* arena, const AutoLockGC& lock) { Arena* next; for (; arena; arena = next) { next = arena->next; rt->gc.releaseArena(arena, lock); } } ArenaLists::~ArenaLists() { AutoLockGC lock(runtime_); for (auto i : AllAllocKinds()) { /* * We can only call this during the shutdown after the last GC when * the background finalization is disabled. */ MOZ_ASSERT(backgroundFinalizeState[i] == BFS_DONE); ReleaseArenaList(runtime_, arenaLists[i].head(), lock); } ReleaseArenaList(runtime_, incrementalSweptArenas.head(), lock); for (auto i : ObjectAllocKinds()) ReleaseArenaList(runtime_, savedObjectArenas[i].head(), lock); ReleaseArenaList(runtime_, savedEmptyObjectArenas, lock); } void ArenaLists::finalizeNow(FreeOp* fop, const FinalizePhase& phase) { gcstats::AutoPhase ap(fop->runtime()->gc.stats, phase.statsPhase); for (auto kind : phase.kinds) finalizeNow(fop, kind, RELEASE_ARENAS, nullptr); } void ArenaLists::finalizeNow(FreeOp* fop, AllocKind thingKind, KeepArenasEnum keepArenas, Arena** empty) { MOZ_ASSERT(!IsBackgroundFinalized(thingKind)); forceFinalizeNow(fop, thingKind, keepArenas, empty); } void ArenaLists::forceFinalizeNow(FreeOp* fop, AllocKind thingKind, KeepArenasEnum keepArenas, Arena** empty) { MOZ_ASSERT(backgroundFinalizeState[thingKind] == BFS_DONE); Arena* arenas = arenaLists[thingKind].head(); if (!arenas) return; arenaLists[thingKind].clear(); size_t thingsPerArena = Arena::thingsPerArena(thingKind); SortedArenaList finalizedSorted(thingsPerArena); auto unlimited = SliceBudget::unlimited(); FinalizeArenas(fop, &arenas, finalizedSorted, thingKind, unlimited, keepArenas); MOZ_ASSERT(!arenas); if (empty) { MOZ_ASSERT(keepArenas == KEEP_ARENAS); finalizedSorted.extractEmpty(empty); } arenaLists[thingKind] = finalizedSorted.toArenaList(); } void ArenaLists::queueForForegroundSweep(FreeOp* fop, const FinalizePhase& phase) { gcstats::AutoPhase ap(fop->runtime()->gc.stats, phase.statsPhase); for (auto kind : phase.kinds) queueForForegroundSweep(fop, kind); } void ArenaLists::queueForForegroundSweep(FreeOp* fop, AllocKind thingKind) { MOZ_ASSERT(!IsBackgroundFinalized(thingKind)); MOZ_ASSERT(backgroundFinalizeState[thingKind] == BFS_DONE); MOZ_ASSERT(!arenaListsToSweep[thingKind]); arenaListsToSweep[thingKind] = arenaLists[thingKind].head(); arenaLists[thingKind].clear(); } void ArenaLists::queueForBackgroundSweep(FreeOp* fop, const FinalizePhase& phase) { gcstats::AutoPhase ap(fop->runtime()->gc.stats, phase.statsPhase); for (auto kind : phase.kinds) queueForBackgroundSweep(fop, kind); } inline void ArenaLists::queueForBackgroundSweep(FreeOp* fop, AllocKind thingKind) { MOZ_ASSERT(IsBackgroundFinalized(thingKind)); ArenaList* al = &arenaLists[thingKind]; if (al->isEmpty()) { MOZ_ASSERT(backgroundFinalizeState[thingKind] == BFS_DONE); return; } MOZ_ASSERT(backgroundFinalizeState[thingKind] == BFS_DONE); arenaListsToSweep[thingKind] = al->head(); al->clear(); backgroundFinalizeState[thingKind] = BFS_RUN; } /*static*/ void ArenaLists::backgroundFinalize(FreeOp* fop, Arena* listHead, Arena** empty) { MOZ_ASSERT(listHead); MOZ_ASSERT(empty); AllocKind thingKind = listHead->getAllocKind(); Zone* zone = listHead->zone; size_t thingsPerArena = Arena::thingsPerArena(thingKind); SortedArenaList finalizedSorted(thingsPerArena); auto unlimited = SliceBudget::unlimited(); FinalizeArenas(fop, &listHead, finalizedSorted, thingKind, unlimited, KEEP_ARENAS); MOZ_ASSERT(!listHead); finalizedSorted.extractEmpty(empty); // When arenas are queued for background finalization, all arenas are moved // to arenaListsToSweep[], leaving the arenaLists[] empty. However, new // arenas may be allocated before background finalization finishes; now that // finalization is complete, we want to merge these lists back together. ArenaLists* lists = &zone->arenas; ArenaList* al = &lists->arenaLists[thingKind]; // Flatten |finalizedSorted| into a regular ArenaList. ArenaList finalized = finalizedSorted.toArenaList(); // We must take the GC lock to be able to safely modify the ArenaList; // however, this does not by itself make the changes visible to all threads, // as not all threads take the GC lock to read the ArenaLists. // That safety is provided by the ReleaseAcquire memory ordering of the // background finalize state, which we explicitly set as the final step. { AutoLockGC lock(lists->runtime_); MOZ_ASSERT(lists->backgroundFinalizeState[thingKind] == BFS_RUN); // Join |al| and |finalized| into a single list. *al = finalized.insertListWithCursorAtEnd(*al); lists->arenaListsToSweep[thingKind] = nullptr; } lists->backgroundFinalizeState[thingKind] = BFS_DONE; } void ArenaLists::queueForegroundObjectsForSweep(FreeOp* fop) { gcstats::AutoPhase ap(fop->runtime()->gc.stats, gcstats::PHASE_SWEEP_OBJECT); #ifdef DEBUG for (auto i : ObjectAllocKinds()) MOZ_ASSERT(savedObjectArenas[i].isEmpty()); MOZ_ASSERT(savedEmptyObjectArenas == nullptr); #endif // Foreground finalized objects must be finalized at the beginning of the // sweep phase, before control can return to the mutator. Otherwise, // mutator behavior can resurrect certain objects whose references would // otherwise have been erased by the finalizer. finalizeNow(fop, AllocKind::OBJECT0, KEEP_ARENAS, &savedEmptyObjectArenas); finalizeNow(fop, AllocKind::OBJECT2, KEEP_ARENAS, &savedEmptyObjectArenas); finalizeNow(fop, AllocKind::OBJECT4, KEEP_ARENAS, &savedEmptyObjectArenas); finalizeNow(fop, AllocKind::OBJECT8, KEEP_ARENAS, &savedEmptyObjectArenas); finalizeNow(fop, AllocKind::OBJECT12, KEEP_ARENAS, &savedEmptyObjectArenas); finalizeNow(fop, AllocKind::OBJECT16, KEEP_ARENAS, &savedEmptyObjectArenas); // Prevent the arenas from having new objects allocated into them. We need // to know which objects are marked while we incrementally sweep dead // references from type information. savedObjectArenas[AllocKind::OBJECT0] = arenaLists[AllocKind::OBJECT0].copyAndClear(); savedObjectArenas[AllocKind::OBJECT2] = arenaLists[AllocKind::OBJECT2].copyAndClear(); savedObjectArenas[AllocKind::OBJECT4] = arenaLists[AllocKind::OBJECT4].copyAndClear(); savedObjectArenas[AllocKind::OBJECT8] = arenaLists[AllocKind::OBJECT8].copyAndClear(); savedObjectArenas[AllocKind::OBJECT12] = arenaLists[AllocKind::OBJECT12].copyAndClear(); savedObjectArenas[AllocKind::OBJECT16] = arenaLists[AllocKind::OBJECT16].copyAndClear(); } void ArenaLists::mergeForegroundSweptObjectArenas() { AutoLockGC lock(runtime_); ReleaseArenaList(runtime_, savedEmptyObjectArenas, lock); savedEmptyObjectArenas = nullptr; mergeSweptArenas(AllocKind::OBJECT0); mergeSweptArenas(AllocKind::OBJECT2); mergeSweptArenas(AllocKind::OBJECT4); mergeSweptArenas(AllocKind::OBJECT8); mergeSweptArenas(AllocKind::OBJECT12); mergeSweptArenas(AllocKind::OBJECT16); } inline void ArenaLists::mergeSweptArenas(AllocKind thingKind) { ArenaList* al = &arenaLists[thingKind]; ArenaList* saved = &savedObjectArenas[thingKind]; *al = saved->insertListWithCursorAtEnd(*al); saved->clear(); } void ArenaLists::queueForegroundThingsForSweep(FreeOp* fop) { gcShapeArenasToUpdate = arenaListsToSweep[AllocKind::SHAPE]; gcAccessorShapeArenasToUpdate = arenaListsToSweep[AllocKind::ACCESSOR_SHAPE]; gcObjectGroupArenasToUpdate = arenaListsToSweep[AllocKind::OBJECT_GROUP]; gcScriptArenasToUpdate = arenaListsToSweep[AllocKind::SCRIPT]; } SliceBudget::SliceBudget() : timeBudget(UnlimitedTimeBudget), workBudget(UnlimitedWorkBudget) { makeUnlimited(); } SliceBudget::SliceBudget(TimeBudget time) : timeBudget(time), workBudget(UnlimitedWorkBudget) { if (time.budget < 0) { makeUnlimited(); } else { // Note: TimeBudget(0) is equivalent to WorkBudget(CounterReset). deadline = PRMJ_Now() + time.budget * PRMJ_USEC_PER_MSEC; counter = CounterReset; } } SliceBudget::SliceBudget(WorkBudget work) : timeBudget(UnlimitedTimeBudget), workBudget(work) { if (work.budget < 0) { makeUnlimited(); } else { deadline = 0; counter = work.budget; } } int SliceBudget::describe(char* buffer, size_t maxlen) const { if (isUnlimited()) return snprintf(buffer, maxlen, "unlimited"); else if (isWorkBudget()) return snprintf(buffer, maxlen, "work(%" PRId64 ")", workBudget.budget); else return snprintf(buffer, maxlen, "%" PRId64 "ms", timeBudget.budget); } bool SliceBudget::checkOverBudget() { bool over = PRMJ_Now() >= deadline; if (!over) counter = CounterReset; return over; } void js::MarkCompartmentActive(InterpreterFrame* fp) { fp->script()->compartment()->zone()->active = true; } void GCRuntime::requestMajorGC(JS::gcreason::Reason reason) { MOZ_ASSERT(!CurrentThreadIsPerformingGC()); if (majorGCRequested()) return; majorGCTriggerReason = reason; // There's no need to use RequestInterruptUrgent here. It's slower because // it has to interrupt (looping) Ion code, but loops in Ion code that // affect GC will have an explicit interrupt check. rt->requestInterrupt(JSRuntime::RequestInterruptCanWait); } void GCRuntime::requestMinorGC(JS::gcreason::Reason reason) { MOZ_ASSERT(CurrentThreadCanAccessRuntime(rt)); MOZ_ASSERT(!CurrentThreadIsPerformingGC()); if (minorGCRequested()) return; minorGCTriggerReason = reason; // See comment in requestMajorGC. rt->requestInterrupt(JSRuntime::RequestInterruptCanWait); } bool GCRuntime::triggerGC(JS::gcreason::Reason reason) { /* * Don't trigger GCs if this is being called off the main thread from * onTooMuchMalloc(). */ if (!CurrentThreadCanAccessRuntime(rt)) return false; /* GC is already running. */ if (rt->isHeapCollecting()) return false; JS::PrepareForFullGC(rt->contextFromMainThread()); requestMajorGC(reason); return true; } void GCRuntime::maybeAllocTriggerZoneGC(Zone* zone, const AutoLockGC& lock) { size_t usedBytes = zone->usage.gcBytes(); size_t thresholdBytes = zone->threshold.gcTriggerBytes(); size_t igcThresholdBytes = thresholdBytes * tunables.zoneAllocThresholdFactor(); if (usedBytes >= thresholdBytes) { // The threshold has been surpassed, immediately trigger a GC, // which will be done non-incrementally. triggerZoneGC(zone, JS::gcreason::ALLOC_TRIGGER); } else if (usedBytes >= igcThresholdBytes) { // Reduce the delay to the start of the next incremental slice. if (zone->gcDelayBytes < ArenaSize) zone->gcDelayBytes = 0; else zone->gcDelayBytes -= ArenaSize; if (!zone->gcDelayBytes) { // Start or continue an in progress incremental GC. We do this // to try to avoid performing non-incremental GCs on zones // which allocate a lot of data, even when incremental slices // can't be triggered via scheduling in the event loop. triggerZoneGC(zone, JS::gcreason::ALLOC_TRIGGER); // Delay the next slice until a certain amount of allocation // has been performed. zone->gcDelayBytes = tunables.zoneAllocDelayBytes(); } } } bool GCRuntime::triggerZoneGC(Zone* zone, JS::gcreason::Reason reason) { /* Zones in use by a thread with an exclusive context can't be collected. */ if (!CurrentThreadCanAccessRuntime(rt)) { MOZ_ASSERT(zone->usedByExclusiveThread || zone->isAtomsZone()); return false; } /* GC is already running. */ if (rt->isHeapCollecting()) return false; if (zone->isAtomsZone()) { /* We can't do a zone GC of the atoms compartment. */ if (rt->keepAtoms()) { /* Skip GC and retrigger later, since atoms zone won't be collected * if keepAtoms is true. */ fullGCForAtomsRequested_ = true; return false; } MOZ_RELEASE_ASSERT(triggerGC(reason)); return true; } PrepareZoneForGC(zone); requestMajorGC(reason); return true; } void GCRuntime::maybeGC(Zone* zone) { MOZ_ASSERT(CurrentThreadCanAccessRuntime(rt)); if (gcIfRequested()) return; if (zone->usage.gcBytes() > 1024 * 1024 && zone->usage.gcBytes() >= zone->threshold.allocTrigger(schedulingState.inHighFrequencyGCMode()) && !isIncrementalGCInProgress() && !isBackgroundSweeping()) { PrepareZoneForGC(zone); startGC(GC_NORMAL, JS::gcreason::EAGER_ALLOC_TRIGGER); } } // Do all possible decommit immediately from the current thread without // releasing the GC lock or allocating any memory. void GCRuntime::decommitAllWithoutUnlocking(const AutoLockGC& lock) { MOZ_ASSERT(emptyChunks(lock).count() == 0); for (ChunkPool::Iter chunk(availableChunks(lock)); !chunk.done(); chunk.next()) chunk->decommitAllArenasWithoutUnlocking(lock); MOZ_ASSERT(availableChunks(lock).verify()); } void GCRuntime::startDecommit() { MOZ_ASSERT(CurrentThreadCanAccessRuntime(rt)); MOZ_ASSERT(!decommitTask.isRunning()); // If we are allocating heavily enough to trigger "high freqency" GC, then // skip decommit so that we do not compete with the mutator. if (schedulingState.inHighFrequencyGCMode()) return; BackgroundDecommitTask::ChunkVector toDecommit; { AutoLockGC lock(rt); // Verify that all entries in the empty chunks pool are already decommitted. for (ChunkPool::Iter chunk(emptyChunks(lock)); !chunk.done(); chunk.next()) MOZ_ASSERT(!chunk->info.numArenasFreeCommitted); // Since we release the GC lock while doing the decommit syscall below, // it is dangerous to iterate the available list directly, as the main // thread could modify it concurrently. Instead, we build and pass an // explicit Vector containing the Chunks we want to visit. MOZ_ASSERT(availableChunks(lock).verify()); for (ChunkPool::Iter iter(availableChunks(lock)); !iter.done(); iter.next()) { if (!toDecommit.append(iter.get())) { // The OOM handler does a full, immediate decommit. return onOutOfMallocMemory(lock); } } } decommitTask.setChunksToScan(toDecommit); if (sweepOnBackgroundThread && decommitTask.start()) return; decommitTask.runFromMainThread(rt); } void js::gc::BackgroundDecommitTask::setChunksToScan(ChunkVector &chunks) { MOZ_ASSERT(CurrentThreadCanAccessRuntime(runtime)); MOZ_ASSERT(!isRunning()); MOZ_ASSERT(toDecommit.empty()); Swap(toDecommit, chunks); } /* virtual */ void js::gc::BackgroundDecommitTask::run() { AutoLockGC lock(runtime); for (Chunk* chunk : toDecommit) { // The arena list is not doubly-linked, so we have to work in the free // list order and not in the natural order. while (chunk->info.numArenasFreeCommitted) { bool ok = chunk->decommitOneFreeArena(runtime, lock); // If we are low enough on memory that we can't update the page // tables, or if we need to return for any other reason, break out // of the loop. if (cancel_ || !ok) break; } } toDecommit.clearAndFree(); ChunkPool toFree = runtime->gc.expireEmptyChunkPool(lock); if (toFree.count()) { AutoUnlockGC unlock(lock); FreeChunkPool(runtime, toFree); } } void GCRuntime::sweepBackgroundThings(ZoneList& zones, LifoAlloc& freeBlocks) { freeBlocks.freeAll(); if (zones.isEmpty()) return; // We must finalize thing kinds in the order specified by BackgroundFinalizePhases. Arena* emptyArenas = nullptr; FreeOp fop(nullptr); for (unsigned phase = 0 ; phase < ArrayLength(BackgroundFinalizePhases) ; ++phase) { for (Zone* zone = zones.front(); zone; zone = zone->nextZone()) { for (auto kind : BackgroundFinalizePhases[phase].kinds) { Arena* arenas = zone->arenas.arenaListsToSweep[kind]; MOZ_RELEASE_ASSERT(uintptr_t(arenas) != uintptr_t(-1)); if (arenas) ArenaLists::backgroundFinalize(&fop, arenas, &emptyArenas); } } } AutoLockGC lock(rt); // Release swept arenas, dropping and reaquiring the lock every so often to // avoid blocking the main thread from allocating chunks. static const size_t LockReleasePeriod = 32; size_t releaseCount = 0; Arena* next; for (Arena* arena = emptyArenas; arena; arena = next) { next = arena->next; rt->gc.releaseArena(arena, lock); releaseCount++; if (releaseCount % LockReleasePeriod == 0) { lock.unlock(); lock.lock(); } } while (!zones.isEmpty()) zones.removeFront(); } void GCRuntime::assertBackgroundSweepingFinished() { #ifdef DEBUG MOZ_ASSERT(backgroundSweepZones.isEmpty()); for (ZonesIter zone(rt, WithAtoms); !zone.done(); zone.next()) { for (auto i : AllAllocKinds()) { MOZ_ASSERT(!zone->arenas.arenaListsToSweep[i]); MOZ_ASSERT(zone->arenas.doneBackgroundFinalize(i)); } } MOZ_ASSERT(blocksToFreeAfterSweeping.computedSizeOfExcludingThis() == 0); #endif } unsigned js::GetCPUCount() { static unsigned ncpus = 0; if (ncpus == 0) { # ifdef XP_WIN SYSTEM_INFO sysinfo; GetSystemInfo(&sysinfo); ncpus = unsigned(sysinfo.dwNumberOfProcessors); # else long n = sysconf(_SC_NPROCESSORS_ONLN); ncpus = (n > 0) ? unsigned(n) : 1; # endif } return ncpus; } void GCHelperState::finish() { // Wait for any lingering background sweeping to finish. waitBackgroundSweepEnd(); } GCHelperState::State GCHelperState::state(const AutoLockGC&) { return state_; } void GCHelperState::setState(State state, const AutoLockGC&) { state_ = state; } void GCHelperState::startBackgroundThread(State newState, const AutoLockGC& lock, const AutoLockHelperThreadState& helperLock) { MOZ_ASSERT(!thread && state(lock) == IDLE && newState != IDLE); setState(newState, lock); { AutoEnterOOMUnsafeRegion noOOM; if (!HelperThreadState().gcHelperWorklist(helperLock).append(this)) noOOM.crash("Could not add to pending GC helpers list"); } HelperThreadState().notifyAll(GlobalHelperThreadState::PRODUCER, helperLock); } void GCHelperState::waitForBackgroundThread(js::AutoLockGC& lock) { done.wait(lock.guard()); } void GCHelperState::work() { MOZ_ASSERT(CanUseExtraThreads()); AutoLockGC lock(rt); MOZ_ASSERT(thread.isNothing()); thread = mozilla::Some(ThisThread::GetId()); TraceLoggerThread* logger = TraceLoggerForCurrentThread(); switch (state(lock)) { case IDLE: MOZ_CRASH("GC helper triggered on idle state"); break; case SWEEPING: { AutoTraceLog logSweeping(logger, TraceLogger_GCSweeping); doSweep(lock); MOZ_ASSERT(state(lock) == SWEEPING); break; } } setState(IDLE, lock); thread.reset(); done.notify_all(); } void GCRuntime::queueZonesForBackgroundSweep(ZoneList& zones) { AutoLockHelperThreadState helperLock; AutoLockGC lock(rt); backgroundSweepZones.transferFrom(zones); helperState.maybeStartBackgroundSweep(lock, helperLock); } void GCRuntime::freeUnusedLifoBlocksAfterSweeping(LifoAlloc* lifo) { MOZ_ASSERT(rt->isHeapBusy()); AutoLockGC lock(rt); blocksToFreeAfterSweeping.transferUnusedFrom(lifo); } void GCRuntime::freeAllLifoBlocksAfterSweeping(LifoAlloc* lifo) { MOZ_ASSERT(rt->isHeapBusy()); AutoLockGC lock(rt); blocksToFreeAfterSweeping.transferFrom(lifo); } void GCRuntime::freeAllLifoBlocksAfterMinorGC(LifoAlloc* lifo) { MOZ_ASSERT(CurrentThreadCanAccessRuntime(rt)); blocksToFreeAfterMinorGC.transferFrom(lifo); } void GCHelperState::maybeStartBackgroundSweep(const AutoLockGC& lock, const AutoLockHelperThreadState& helperLock) { MOZ_ASSERT(CanUseExtraThreads()); if (state(lock) == IDLE) startBackgroundThread(SWEEPING, lock, helperLock); } void GCHelperState::waitBackgroundSweepEnd() { AutoLockGC lock(rt); while (state(lock) == SWEEPING) waitForBackgroundThread(lock); if (!rt->gc.isIncrementalGCInProgress()) rt->gc.assertBackgroundSweepingFinished(); } void GCHelperState::doSweep(AutoLockGC& lock) { // The main thread may call queueZonesForBackgroundSweep() while this is // running so we must check there is no more work to do before exiting. do { while (!rt->gc.backgroundSweepZones.isEmpty()) { AutoSetThreadIsSweeping threadIsSweeping; ZoneList zones; zones.transferFrom(rt->gc.backgroundSweepZones); LifoAlloc freeLifoAlloc(JSRuntime::TEMP_LIFO_ALLOC_PRIMARY_CHUNK_SIZE); freeLifoAlloc.transferFrom(&rt->gc.blocksToFreeAfterSweeping); AutoUnlockGC unlock(lock); rt->gc.sweepBackgroundThings(zones, freeLifoAlloc); } } while (!rt->gc.backgroundSweepZones.isEmpty()); } bool GCHelperState::onBackgroundThread() { return thread.isSome() && *thread == ThisThread::GetId(); } bool GCRuntime::shouldReleaseObservedTypes() { bool releaseTypes = false; /* We may miss the exact target GC due to resets. */ if (majorGCNumber >= jitReleaseNumber) releaseTypes = true; if (releaseTypes) jitReleaseNumber = majorGCNumber + JIT_SCRIPT_RELEASE_TYPES_PERIOD; return releaseTypes; } struct IsAboutToBeFinalizedFunctor { template <typename T> bool operator()(Cell** t) { mozilla::DebugOnly<const Cell*> prior = *t; bool result = IsAboutToBeFinalizedUnbarriered(reinterpret_cast<T**>(t)); // Sweep should not have to deal with moved pointers, since moving GC // handles updating the UID table manually. MOZ_ASSERT(*t == prior); return result; } }; /* static */ bool UniqueIdGCPolicy::needsSweep(Cell** cell, uint64_t*) { return DispatchTraceKindTyped(IsAboutToBeFinalizedFunctor(), (*cell)->getTraceKind(), cell); } void JS::Zone::sweepUniqueIds(js::FreeOp* fop) { uniqueIds_.sweep(); } /* * It's simpler if we preserve the invariant that every zone has at least one * compartment. If we know we're deleting the entire zone, then * SweepCompartments is allowed to delete all compartments. In this case, * |keepAtleastOne| is false. If some objects remain in the zone so that it * cannot be deleted, then we set |keepAtleastOne| to true, which prohibits * SweepCompartments from deleting every compartment. Instead, it preserves an * arbitrary compartment in the zone. */ void Zone::sweepCompartments(FreeOp* fop, bool keepAtleastOne, bool destroyingRuntime) { JSRuntime* rt = runtimeFromMainThread(); JSDestroyCompartmentCallback callback = rt->destroyCompartmentCallback; JSCompartment** read = compartments.begin(); JSCompartment** end = compartments.end(); JSCompartment** write = read; bool foundOne = false; while (read < end) { JSCompartment* comp = *read++; MOZ_ASSERT(!rt->isAtomsCompartment(comp)); /* * Don't delete the last compartment if all the ones before it were * deleted and keepAtleastOne is true. */ bool dontDelete = read == end && !foundOne && keepAtleastOne; if ((!comp->marked && !dontDelete) || destroyingRuntime) { if (callback) callback(fop, comp); if (comp->principals()) JS_DropPrincipals(rt->contextFromMainThread(), comp->principals()); js_delete(comp); rt->gc.stats.sweptCompartment(); } else { *write++ = comp; foundOne = true; } } compartments.shrinkTo(write - compartments.begin()); MOZ_ASSERT_IF(keepAtleastOne, !compartments.empty()); } void GCRuntime::sweepZones(FreeOp* fop, bool destroyingRuntime) { MOZ_ASSERT_IF(destroyingRuntime, numActiveZoneIters == 0); MOZ_ASSERT_IF(destroyingRuntime, arenasEmptyAtShutdown); if (rt->gc.numActiveZoneIters) return; assertBackgroundSweepingFinished(); JSZoneCallback callback = rt->destroyZoneCallback; /* Skip the atomsCompartment zone. */ Zone** read = zones.begin() + 1; Zone** end = zones.end(); Zone** write = read; MOZ_ASSERT(zones.length() >= 1); MOZ_ASSERT(zones[0]->isAtomsZone()); while (read < end) { Zone* zone = *read++; if (zone->wasGCStarted()) { MOZ_ASSERT(!zone->isQueuedForBackgroundSweep()); const bool zoneIsDead = zone->arenas.arenaListsAreEmpty() && !zone->hasMarkedCompartments(); if (zoneIsDead || destroyingRuntime) { // We have just finished sweeping, so we should have freed any // empty arenas back to their Chunk for future allocation. zone->arenas.checkEmptyFreeLists(); // We are about to delete the Zone; this will leave the Zone* // in the arena header dangling if there are any arenas // remaining at this point. #ifdef DEBUG if (!zone->arenas.checkEmptyArenaLists()) arenasEmptyAtShutdown = false; #endif if (callback) callback(zone); zone->sweepCompartments(fop, false, destroyingRuntime); MOZ_ASSERT(zone->compartments.empty()); MOZ_ASSERT_IF(arenasEmptyAtShutdown, zone->typeDescrObjects.empty()); fop->delete_(zone); stats.sweptZone(); continue; } zone->sweepCompartments(fop, true, destroyingRuntime); } *write++ = zone; } zones.shrinkTo(write - zones.begin()); } #ifdef DEBUG static const char* AllocKindToAscii(AllocKind kind) { switch(kind) { #define MAKE_CASE(allocKind, traceKind, type, sizedType) \ case AllocKind:: allocKind: return #allocKind; FOR_EACH_ALLOCKIND(MAKE_CASE) #undef MAKE_CASE default: MOZ_CRASH("Unknown AllocKind in AllocKindToAscii"); } } #endif // DEBUG bool ArenaLists::checkEmptyArenaList(AllocKind kind) { size_t num_live = 0; #ifdef DEBUG if (!arenaLists[kind].isEmpty()) { size_t max_cells = 20; char *env = getenv("JS_GC_MAX_LIVE_CELLS"); if (env && *env) max_cells = atol(env); for (Arena* current = arenaLists[kind].head(); current; current = current->next) { for (ArenaCellIterUnderGC i(current); !i.done(); i.next()) { TenuredCell* t = i.getCell(); MOZ_ASSERT(t->isMarked(), "unmarked cells should have been finalized"); if (++num_live <= max_cells) { fprintf(stderr, "ERROR: GC found live Cell %p of kind %s at shutdown\n", t, AllocKindToAscii(kind)); } } } fprintf(stderr, "ERROR: GC found %" PRIuSIZE " live Cells at shutdown\n", num_live); } #endif // DEBUG return num_live == 0; } void GCRuntime::purgeRuntime(AutoLockForExclusiveAccess& lock) { for (GCCompartmentsIter comp(rt); !comp.done(); comp.next()) comp->purge(); freeUnusedLifoBlocksAfterSweeping(&rt->tempLifoAlloc); rt->interpreterStack().purge(rt); JSContext* cx = rt->contextFromMainThread(); cx->caches.gsnCache.purge(); cx->caches.envCoordinateNameCache.purge(); cx->caches.newObjectCache.purge(); cx->caches.nativeIterCache.purge(); cx->caches.uncompressedSourceCache.purge(); if (cx->caches.evalCache.initialized()) cx->caches.evalCache.clear(); rt->mainThread.frontendCollectionPool.purge(); if (auto cache = rt->maybeThisRuntimeSharedImmutableStrings()) cache->purge(); rt->promiseTasksToDestroy.lock()->clear(); } bool GCRuntime::shouldPreserveJITCode(JSCompartment* comp, int64_t currentTime, JS::gcreason::Reason reason, bool canAllocateMoreCode) { if (cleanUpEverything) return false; if (!canAllocateMoreCode) return false; if (alwaysPreserveCode) return true; if (comp->preserveJitCode()) return true; if (comp->lastAnimationTime + PRMJ_USEC_PER_SEC >= currentTime) return true; if (reason == JS::gcreason::DEBUG_GC) return true; return false; } #ifdef DEBUG class CompartmentCheckTracer : public JS::CallbackTracer { void onChild(const JS::GCCellPtr& thing) override; public: explicit CompartmentCheckTracer(JSRuntime* rt) : JS::CallbackTracer(rt), src(nullptr), zone(nullptr), compartment(nullptr) {} Cell* src; JS::TraceKind srcKind; Zone* zone; JSCompartment* compartment; }; namespace { struct IsDestComparatorFunctor { JS::GCCellPtr dst_; explicit IsDestComparatorFunctor(JS::GCCellPtr dst) : dst_(dst) {} template <typename T> bool operator()(T* t) { return (*t) == dst_.asCell(); } }; } // namespace (anonymous) static bool InCrossCompartmentMap(JSObject* src, JS::GCCellPtr dst) { JSCompartment* srccomp = src->compartment(); if (dst.is<JSObject>()) { Value key = ObjectValue(dst.as<JSObject>()); if (WrapperMap::Ptr p = srccomp->lookupWrapper(key)) { if (*p->value().unsafeGet() == ObjectValue(*src)) return true; } } /* * If the cross-compartment edge is caused by the debugger, then we don't * know the right hashtable key, so we have to iterate. */ for (JSCompartment::WrapperEnum e(srccomp); !e.empty(); e.popFront()) { if (e.front().mutableKey().applyToWrapped(IsDestComparatorFunctor(dst)) && ToMarkable(e.front().value().unbarrieredGet()) == src) { return true; } } return false; } struct MaybeCompartmentFunctor { template <typename T> JSCompartment* operator()(T* t) { return t->maybeCompartment(); } }; void CompartmentCheckTracer::onChild(const JS::GCCellPtr& thing) { JSCompartment* comp = DispatchTyped(MaybeCompartmentFunctor(), thing); if (comp && compartment) { MOZ_ASSERT(comp == compartment || runtime()->isAtomsCompartment(comp) || (srcKind == JS::TraceKind::Object && InCrossCompartmentMap(static_cast<JSObject*>(src), thing))); } else { TenuredCell* tenured = TenuredCell::fromPointer(thing.asCell()); Zone* thingZone = tenured->zoneFromAnyThread(); MOZ_ASSERT(thingZone == zone || thingZone->isAtomsZone()); } } void GCRuntime::checkForCompartmentMismatches() { if (disableStrictProxyCheckingCount) return; CompartmentCheckTracer trc(rt); AutoAssertEmptyNursery empty(rt); for (ZonesIter zone(rt, SkipAtoms); !zone.done(); zone.next()) { trc.zone = zone; for (auto thingKind : AllAllocKinds()) { for (auto i = zone->cellIter<TenuredCell>(thingKind, empty); !i.done(); i.next()) { trc.src = i.getCell(); trc.srcKind = MapAllocToTraceKind(thingKind); trc.compartment = DispatchTraceKindTyped(MaybeCompartmentFunctor(), trc.src, trc.srcKind); js::TraceChildren(&trc, trc.src, trc.srcKind); } } } } #endif static void RelazifyFunctions(Zone* zone, AllocKind kind) { MOZ_ASSERT(kind == AllocKind::FUNCTION || kind == AllocKind::FUNCTION_EXTENDED); JSRuntime* rt = zone->runtimeFromMainThread(); AutoAssertEmptyNursery empty(rt); for (auto i = zone->cellIter<JSObject>(kind, empty); !i.done(); i.next()) { JSFunction* fun = &i->as<JSFunction>(); if (fun->hasScript()) fun->maybeRelazify(rt); } } static bool ShouldCollectZone(Zone* zone, JS::gcreason::Reason reason) { // Normally we collect all scheduled zones. if (reason != JS::gcreason::COMPARTMENT_REVIVED) return zone->isGCScheduled(); // If we are repeating a GC because we noticed dead compartments haven't // been collected, then only collect zones containing those compartments. for (CompartmentsInZoneIter comp(zone); !comp.done(); comp.next()) { if (comp->scheduledForDestruction) return true; } return false; } bool GCRuntime::beginMarkPhase(JS::gcreason::Reason reason, AutoLockForExclusiveAccess& lock) { int64_t currentTime = PRMJ_Now(); #ifdef DEBUG if (fullCompartmentChecks) checkForCompartmentMismatches(); #endif isFull = true; bool any = false; for (ZonesIter zone(rt, WithAtoms); !zone.done(); zone.next()) { /* Assert that zone state is as we expect */ MOZ_ASSERT(!zone->isCollecting()); MOZ_ASSERT(!zone->compartments.empty()); #ifdef DEBUG for (auto i : AllAllocKinds()) MOZ_ASSERT(!zone->arenas.arenaListsToSweep[i]); #endif /* Set up which zones will be collected. */ if (ShouldCollectZone(zone, reason)) { if (!zone->isAtomsZone()) { any = true; zone->setGCState(Zone::Mark); } } else { isFull = false; } zone->setPreservingCode(false); } // Discard JIT code more aggressively if the process is approaching its // executable code limit. bool canAllocateMoreCode = jit::CanLikelyAllocateMoreExecutableMemory(); for (CompartmentsIter c(rt, WithAtoms); !c.done(); c.next()) { c->marked = false; c->scheduledForDestruction = false; c->maybeAlive = c->hasBeenEntered() || !c->zone()->isGCScheduled(); if (shouldPreserveJITCode(c, currentTime, reason, canAllocateMoreCode)) c->zone()->setPreservingCode(true); } if (!rt->gc.cleanUpEverything && canAllocateMoreCode) { if (JSCompartment* comp = jit::TopmostIonActivationCompartment(rt)) comp->zone()->setPreservingCode(true); } /* * Atoms are not in the cross-compartment map. So if there are any * zones that are not being collected, we are not allowed to collect * atoms. Otherwise, the non-collected zones could contain pointers * to atoms that we would miss. * * keepAtoms() will only change on the main thread, which we are currently * on. If the value of keepAtoms() changes between GC slices, then we'll * cancel the incremental GC. See IsIncrementalGCSafe. */ if (isFull && !rt->keepAtoms()) { Zone* atomsZone = rt->atomsCompartment(lock)->zone(); if (atomsZone->isGCScheduled()) { MOZ_ASSERT(!atomsZone->isCollecting()); atomsZone->setGCState(Zone::Mark); any = true; } } /* Check that at least one zone is scheduled for collection. */ if (!any) return false; /* * Ensure that after the start of a collection we don't allocate into any * existing arenas, as this can cause unreachable things to be marked. */ if (isIncremental) { for (GCZonesIter zone(rt); !zone.done(); zone.next()) zone->arenas.prepareForIncrementalGC(); } MemProfiler::MarkTenuredStart(rt); marker.start(); GCMarker* gcmarker = ▮ /* For non-incremental GC the following sweep discards the jit code. */ if (isIncremental) { js::CancelOffThreadIonCompile(rt, JS::Zone::Mark); for (GCZonesIter zone(rt); !zone.done(); zone.next()) { gcstats::AutoPhase ap(stats, gcstats::PHASE_MARK_DISCARD_CODE); zone->discardJitCode(rt->defaultFreeOp()); } } /* * Relazify functions after discarding JIT code (we can't relazify * functions with JIT code) and before the actual mark phase, so that * the current GC can collect the JSScripts we're unlinking here. * We do this only when we're performing a shrinking GC, as too much * relazification can cause performance issues when we have to reparse * the same functions over and over. */ if (invocationKind == GC_SHRINK) { { gcstats::AutoPhase ap(stats, gcstats::PHASE_RELAZIFY_FUNCTIONS); for (GCZonesIter zone(rt); !zone.done(); zone.next()) { if (zone->isSelfHostingZone()) continue; RelazifyFunctions(zone, AllocKind::FUNCTION); RelazifyFunctions(zone, AllocKind::FUNCTION_EXTENDED); } } /* Purge ShapeTables. */ gcstats::AutoPhase ap(stats, gcstats::PHASE_PURGE_SHAPE_TABLES); for (GCZonesIter zone(rt); !zone.done(); zone.next()) { if (zone->keepShapeTables() || zone->isSelfHostingZone()) continue; for (auto baseShape = zone->cellIter<BaseShape>(); !baseShape.done(); baseShape.next()) baseShape->maybePurgeTable(); } } startNumber = number; /* * We must purge the runtime at the beginning of an incremental GC. The * danger if we purge later is that the snapshot invariant of incremental * GC will be broken, as follows. If some object is reachable only through * some cache (say the dtoaCache) then it will not be part of the snapshot. * If we purge after root marking, then the mutator could obtain a pointer * to the object and start using it. This object might never be marked, so * a GC hazard would exist. */ { gcstats::AutoPhase ap(stats, gcstats::PHASE_PURGE); purgeRuntime(lock); } /* * Mark phase. */ gcstats::AutoPhase ap1(stats, gcstats::PHASE_MARK); { gcstats::AutoPhase ap(stats, gcstats::PHASE_UNMARK); for (GCZonesIter zone(rt); !zone.done(); zone.next()) { /* Unmark everything in the zones being collected. */ zone->arenas.unmarkAll(); } for (GCZonesIter zone(rt); !zone.done(); zone.next()) { /* Unmark all weak maps in the zones being collected. */ WeakMapBase::unmarkZone(zone); } } traceRuntimeForMajorGC(gcmarker, lock); gcstats::AutoPhase ap2(stats, gcstats::PHASE_MARK_ROOTS); if (isIncremental) { bufferGrayRoots(); markCompartments(); } return true; } void GCRuntime::markCompartments() { gcstats::AutoPhase ap(stats, gcstats::PHASE_MARK_COMPARTMENTS); /* * This code ensures that if a compartment is "dead", then it will be * collected in this GC. A compartment is considered dead if its maybeAlive * flag is false. The maybeAlive flag is set if: * (1) the compartment has been entered (set in beginMarkPhase() above) * (2) the compartment is not being collected (set in beginMarkPhase() * above) * (3) an object in the compartment was marked during root marking, either * as a black root or a gray root (set in RootMarking.cpp), or * (4) the compartment has incoming cross-compartment edges from another * compartment that has maybeAlive set (set by this method). * * If the maybeAlive is false, then we set the scheduledForDestruction flag. * At the end of the GC, we look for compartments where * scheduledForDestruction is true. These are compartments that were somehow * "revived" during the incremental GC. If any are found, we do a special, * non-incremental GC of those compartments to try to collect them. * * Compartments can be revived for a variety of reasons. On reason is bug * 811587, where a reflector that was dead can be revived by DOM code that * still refers to the underlying DOM node. * * Read barriers and allocations can also cause revival. This might happen * during a function like JS_TransplantObject, which iterates over all * compartments, live or dead, and operates on their objects. See bug 803376 * for details on this problem. To avoid the problem, we try to avoid * allocation and read barriers during JS_TransplantObject and the like. */ /* Propagate the maybeAlive flag via cross-compartment edges. */ Vector<JSCompartment*, 0, js::SystemAllocPolicy> workList; for (CompartmentsIter comp(rt, SkipAtoms); !comp.done(); comp.next()) { if (comp->maybeAlive) { if (!workList.append(comp)) return; } } while (!workList.empty()) { JSCompartment* comp = workList.popCopy(); for (JSCompartment::WrapperEnum e(comp); !e.empty(); e.popFront()) { if (e.front().key().is<JSString*>()) continue; JSCompartment* dest = e.front().mutableKey().compartment(); if (dest && !dest->maybeAlive) { dest->maybeAlive = true; if (!workList.append(dest)) return; } } } /* Set scheduleForDestruction based on maybeAlive. */ for (GCCompartmentsIter comp(rt); !comp.done(); comp.next()) { MOZ_ASSERT(!comp->scheduledForDestruction); if (!comp->maybeAlive && !rt->isAtomsCompartment(comp)) comp->scheduledForDestruction = true; } } template <class ZoneIterT> void GCRuntime::markWeakReferences(gcstats::Phase phase) { MOZ_ASSERT(marker.isDrained()); gcstats::AutoPhase ap1(stats, phase); marker.enterWeakMarkingMode(); // TODO bug 1167452: Make weak marking incremental auto unlimited = SliceBudget::unlimited(); MOZ_RELEASE_ASSERT(marker.drainMarkStack(unlimited)); for (;;) { bool markedAny = false; if (!marker.isWeakMarkingTracer()) { for (ZoneIterT zone(rt); !zone.done(); zone.next()) markedAny |= WeakMapBase::markZoneIteratively(zone, &marker); } for (CompartmentsIterT<ZoneIterT> c(rt); !c.done(); c.next()) { if (c->watchpointMap) markedAny |= c->watchpointMap->markIteratively(&marker); } markedAny |= Debugger::markAllIteratively(&marker); markedAny |= jit::JitRuntime::MarkJitcodeGlobalTableIteratively(&marker); if (!markedAny) break; auto unlimited = SliceBudget::unlimited(); MOZ_RELEASE_ASSERT(marker.drainMarkStack(unlimited)); } MOZ_ASSERT(marker.isDrained()); marker.leaveWeakMarkingMode(); } void GCRuntime::markWeakReferencesInCurrentGroup(gcstats::Phase phase) { markWeakReferences<GCZoneGroupIter>(phase); } template <class ZoneIterT, class CompartmentIterT> void GCRuntime::markGrayReferences(gcstats::Phase phase) { gcstats::AutoPhase ap(stats, phase); if (hasBufferedGrayRoots()) { for (ZoneIterT zone(rt); !zone.done(); zone.next()) markBufferedGrayRoots(zone); } else { MOZ_ASSERT(!isIncremental); if (JSTraceDataOp op = grayRootTracer.op) (*op)(&marker, grayRootTracer.data); } auto unlimited = SliceBudget::unlimited(); MOZ_RELEASE_ASSERT(marker.drainMarkStack(unlimited)); } void GCRuntime::markGrayReferencesInCurrentGroup(gcstats::Phase phase) { markGrayReferences<GCZoneGroupIter, GCCompartmentGroupIter>(phase); } void GCRuntime::markAllWeakReferences(gcstats::Phase phase) { markWeakReferences<GCZonesIter>(phase); } void GCRuntime::markAllGrayReferences(gcstats::Phase phase) { markGrayReferences<GCZonesIter, GCCompartmentsIter>(phase); } static void DropStringWrappers(JSRuntime* rt) { /* * String "wrappers" are dropped on GC because their presence would require * us to sweep the wrappers in all compartments every time we sweep a * compartment group. */ for (CompartmentsIter c(rt, SkipAtoms); !c.done(); c.next()) { for (JSCompartment::WrapperEnum e(c); !e.empty(); e.popFront()) { if (e.front().key().is<JSString*>()) e.removeFront(); } } } /* * Group zones that must be swept at the same time. * * If compartment A has an edge to an unmarked object in compartment B, then we * must not sweep A in a later slice than we sweep B. That's because a write * barrier in A could lead to the unmarked object in B becoming marked. * However, if we had already swept that object, we would be in trouble. * * If we consider these dependencies as a graph, then all the compartments in * any strongly-connected component of this graph must be swept in the same * slice. * * Tarjan's algorithm is used to calculate the components. */ namespace { struct AddOutgoingEdgeFunctor { bool needsEdge_; ZoneComponentFinder& finder_; AddOutgoingEdgeFunctor(bool needsEdge, ZoneComponentFinder& finder) : needsEdge_(needsEdge), finder_(finder) {} template <typename T> void operator()(T tp) { TenuredCell& other = (*tp)->asTenured(); /* * Add edge to wrapped object compartment if wrapped object is not * marked black to indicate that wrapper compartment not be swept * after wrapped compartment. */ if (needsEdge_) { JS::Zone* zone = other.zone(); if (zone->isGCMarking()) finder_.addEdgeTo(zone); } } }; } // namespace (anonymous) void JSCompartment::findOutgoingEdges(ZoneComponentFinder& finder) { for (js::WrapperMap::Enum e(crossCompartmentWrappers); !e.empty(); e.popFront()) { CrossCompartmentKey& key = e.front().mutableKey(); MOZ_ASSERT(!key.is<JSString*>()); bool needsEdge = true; if (key.is<JSObject*>()) { TenuredCell& other = key.as<JSObject*>()->asTenured(); needsEdge = !other.isMarked(BLACK) || other.isMarked(GRAY); } key.applyToWrapped(AddOutgoingEdgeFunctor(needsEdge, finder)); } } void Zone::findOutgoingEdges(ZoneComponentFinder& finder) { /* * Any compartment may have a pointer to an atom in the atoms * compartment, and these aren't in the cross compartment map. */ JSRuntime* rt = runtimeFromMainThread(); Zone* atomsZone = rt->atomsCompartment(finder.lock)->zone(); if (atomsZone->isGCMarking()) finder.addEdgeTo(atomsZone); for (CompartmentsInZoneIter comp(this); !comp.done(); comp.next()) comp->findOutgoingEdges(finder); for (ZoneSet::Range r = gcZoneGroupEdges.all(); !r.empty(); r.popFront()) { if (r.front()->isGCMarking()) finder.addEdgeTo(r.front()); } Debugger::findZoneEdges(this, finder); } bool GCRuntime::findInterZoneEdges() { /* * Weakmaps which have keys with delegates in a different zone introduce the * need for zone edges from the delegate's zone to the weakmap zone. * * Since the edges point into and not away from the zone the weakmap is in * we must find these edges in advance and store them in a set on the Zone. * If we run out of memory, we fall back to sweeping everything in one * group. */ for (GCZonesIter zone(rt); !zone.done(); zone.next()) { if (!WeakMapBase::findInterZoneEdges(zone)) return false; } return true; } void GCRuntime::findZoneGroups(AutoLockForExclusiveAccess& lock) { #ifdef DEBUG for (ZonesIter zone(rt, WithAtoms); !zone.done(); zone.next()) MOZ_ASSERT(zone->gcZoneGroupEdges.empty()); #endif JSContext* cx = rt->contextFromMainThread(); ZoneComponentFinder finder(cx->nativeStackLimit[StackForSystemCode], lock); if (!isIncremental || !findInterZoneEdges()) finder.useOneComponent(); for (GCZonesIter zone(rt); !zone.done(); zone.next()) { MOZ_ASSERT(zone->isGCMarking()); finder.addNode(zone); } zoneGroups = finder.getResultsList(); currentZoneGroup = zoneGroups; zoneGroupIndex = 0; for (GCZonesIter zone(rt); !zone.done(); zone.next()) zone->gcZoneGroupEdges.clear(); #ifdef DEBUG for (Zone* head = currentZoneGroup; head; head = head->nextGroup()) { for (Zone* zone = head; zone; zone = zone->nextNodeInGroup()) MOZ_ASSERT(zone->isGCMarking()); } MOZ_ASSERT_IF(!isIncremental, !currentZoneGroup->nextGroup()); for (ZonesIter zone(rt, WithAtoms); !zone.done(); zone.next()) MOZ_ASSERT(zone->gcZoneGroupEdges.empty()); #endif } static void ResetGrayList(JSCompartment* comp); void GCRuntime::getNextZoneGroup() { currentZoneGroup = currentZoneGroup->nextGroup(); ++zoneGroupIndex; if (!currentZoneGroup) { abortSweepAfterCurrentGroup = false; return; } for (Zone* zone = currentZoneGroup; zone; zone = zone->nextNodeInGroup()) { MOZ_ASSERT(zone->isGCMarking()); MOZ_ASSERT(!zone->isQueuedForBackgroundSweep()); } if (!isIncremental) ZoneComponentFinder::mergeGroups(currentZoneGroup); if (abortSweepAfterCurrentGroup) { MOZ_ASSERT(!isIncremental); for (GCZoneGroupIter zone(rt); !zone.done(); zone.next()) { MOZ_ASSERT(!zone->gcNextGraphComponent); MOZ_ASSERT(zone->isGCMarking()); zone->setNeedsIncrementalBarrier(false, Zone::UpdateJit); zone->setGCState(Zone::NoGC); zone->gcGrayRoots.clearAndFree(); } for (GCCompartmentGroupIter comp(rt); !comp.done(); comp.next()) ResetGrayList(comp); abortSweepAfterCurrentGroup = false; currentZoneGroup = nullptr; } } /* * Gray marking: * * At the end of collection, anything reachable from a gray root that has not * otherwise been marked black must be marked gray. * * This means that when marking things gray we must not allow marking to leave * the current compartment group, as that could result in things being marked * grey when they might subsequently be marked black. To achieve this, when we * find a cross compartment pointer we don't mark the referent but add it to a * singly-linked list of incoming gray pointers that is stored with each * compartment. * * The list head is stored in JSCompartment::gcIncomingGrayPointers and contains * cross compartment wrapper objects. The next pointer is stored in the second * extra slot of the cross compartment wrapper. * * The list is created during gray marking when one of the * MarkCrossCompartmentXXX functions is called for a pointer that leaves the * current compartent group. This calls DelayCrossCompartmentGrayMarking to * push the referring object onto the list. * * The list is traversed and then unlinked in * MarkIncomingCrossCompartmentPointers. */ static bool IsGrayListObject(JSObject* obj) { MOZ_ASSERT(obj); return obj->is<CrossCompartmentWrapperObject>() && !IsDeadProxyObject(obj); } /* static */ unsigned ProxyObject::grayLinkExtraSlot(JSObject* obj) { MOZ_ASSERT(IsGrayListObject(obj)); return 1; } #ifdef DEBUG static void AssertNotOnGrayList(JSObject* obj) { MOZ_ASSERT_IF(IsGrayListObject(obj), GetProxyExtra(obj, ProxyObject::grayLinkExtraSlot(obj)).isUndefined()); } #endif static void AssertNoWrappersInGrayList(JSRuntime* rt) { #ifdef DEBUG for (CompartmentsIter c(rt, SkipAtoms); !c.done(); c.next()) { MOZ_ASSERT(!c->gcIncomingGrayPointers); for (JSCompartment::WrapperEnum e(c); !e.empty(); e.popFront()) { if (!e.front().key().is<JSString*>()) AssertNotOnGrayList(&e.front().value().unbarrieredGet().toObject()); } } #endif } static JSObject* CrossCompartmentPointerReferent(JSObject* obj) { MOZ_ASSERT(IsGrayListObject(obj)); return &obj->as<ProxyObject>().private_().toObject(); } static JSObject* NextIncomingCrossCompartmentPointer(JSObject* prev, bool unlink) { unsigned slot = ProxyObject::grayLinkExtraSlot(prev); JSObject* next = GetProxyExtra(prev, slot).toObjectOrNull(); MOZ_ASSERT_IF(next, IsGrayListObject(next)); if (unlink) SetProxyExtra(prev, slot, UndefinedValue()); return next; } void js::DelayCrossCompartmentGrayMarking(JSObject* src) { MOZ_ASSERT(IsGrayListObject(src)); /* Called from MarkCrossCompartmentXXX functions. */ unsigned slot = ProxyObject::grayLinkExtraSlot(src); JSObject* dest = CrossCompartmentPointerReferent(src); JSCompartment* comp = dest->compartment(); if (GetProxyExtra(src, slot).isUndefined()) { SetProxyExtra(src, slot, ObjectOrNullValue(comp->gcIncomingGrayPointers)); comp->gcIncomingGrayPointers = src; } else { MOZ_ASSERT(GetProxyExtra(src, slot).isObjectOrNull()); } #ifdef DEBUG /* * Assert that the object is in our list, also walking the list to check its * integrity. */ JSObject* obj = comp->gcIncomingGrayPointers; bool found = false; while (obj) { if (obj == src) found = true; obj = NextIncomingCrossCompartmentPointer(obj, false); } MOZ_ASSERT(found); #endif } static void MarkIncomingCrossCompartmentPointers(JSRuntime* rt, const uint32_t color) { MOZ_ASSERT(color == BLACK || color == GRAY); static const gcstats::Phase statsPhases[] = { gcstats::PHASE_SWEEP_MARK_INCOMING_BLACK, gcstats::PHASE_SWEEP_MARK_INCOMING_GRAY }; gcstats::AutoPhase ap1(rt->gc.stats, statsPhases[color]); bool unlinkList = color == GRAY; for (GCCompartmentGroupIter c(rt); !c.done(); c.next()) { MOZ_ASSERT_IF(color == GRAY, c->zone()->isGCMarkingGray()); MOZ_ASSERT_IF(color == BLACK, c->zone()->isGCMarkingBlack()); MOZ_ASSERT_IF(c->gcIncomingGrayPointers, IsGrayListObject(c->gcIncomingGrayPointers)); for (JSObject* src = c->gcIncomingGrayPointers; src; src = NextIncomingCrossCompartmentPointer(src, unlinkList)) { JSObject* dst = CrossCompartmentPointerReferent(src); MOZ_ASSERT(dst->compartment() == c); if (color == GRAY) { if (IsMarkedUnbarriered(rt, &src) && src->asTenured().isMarked(GRAY)) TraceManuallyBarrieredEdge(&rt->gc.marker, &dst, "cross-compartment gray pointer"); } else { if (IsMarkedUnbarriered(rt, &src) && !src->asTenured().isMarked(GRAY)) TraceManuallyBarrieredEdge(&rt->gc.marker, &dst, "cross-compartment black pointer"); } } if (unlinkList) c->gcIncomingGrayPointers = nullptr; } auto unlimited = SliceBudget::unlimited(); MOZ_RELEASE_ASSERT(rt->gc.marker.drainMarkStack(unlimited)); } static bool RemoveFromGrayList(JSObject* wrapper) { if (!IsGrayListObject(wrapper)) return false; unsigned slot = ProxyObject::grayLinkExtraSlot(wrapper); if (GetProxyExtra(wrapper, slot).isUndefined()) return false; /* Not on our list. */ JSObject* tail = GetProxyExtra(wrapper, slot).toObjectOrNull(); SetProxyExtra(wrapper, slot, UndefinedValue()); JSCompartment* comp = CrossCompartmentPointerReferent(wrapper)->compartment(); JSObject* obj = comp->gcIncomingGrayPointers; if (obj == wrapper) { comp->gcIncomingGrayPointers = tail; return true; } while (obj) { unsigned slot = ProxyObject::grayLinkExtraSlot(obj); JSObject* next = GetProxyExtra(obj, slot).toObjectOrNull(); if (next == wrapper) { SetProxyExtra(obj, slot, ObjectOrNullValue(tail)); return true; } obj = next; } MOZ_CRASH("object not found in gray link list"); } static void ResetGrayList(JSCompartment* comp) { JSObject* src = comp->gcIncomingGrayPointers; while (src) src = NextIncomingCrossCompartmentPointer(src, true); comp->gcIncomingGrayPointers = nullptr; } void js::NotifyGCNukeWrapper(JSObject* obj) { /* * References to target of wrapper are being removed, we no longer have to * remember to mark it. */ RemoveFromGrayList(obj); } enum { JS_GC_SWAP_OBJECT_A_REMOVED = 1 << 0, JS_GC_SWAP_OBJECT_B_REMOVED = 1 << 1 }; unsigned js::NotifyGCPreSwap(JSObject* a, JSObject* b) { /* * Two objects in the same compartment are about to have had their contents * swapped. If either of them are in our gray pointer list, then we remove * them from the lists, returning a bitset indicating what happened. */ return (RemoveFromGrayList(a) ? JS_GC_SWAP_OBJECT_A_REMOVED : 0) | (RemoveFromGrayList(b) ? JS_GC_SWAP_OBJECT_B_REMOVED : 0); } void js::NotifyGCPostSwap(JSObject* a, JSObject* b, unsigned removedFlags) { /* * Two objects in the same compartment have had their contents swapped. If * either of them were in our gray pointer list, we re-add them again. */ if (removedFlags & JS_GC_SWAP_OBJECT_A_REMOVED) DelayCrossCompartmentGrayMarking(b); if (removedFlags & JS_GC_SWAP_OBJECT_B_REMOVED) DelayCrossCompartmentGrayMarking(a); } void GCRuntime::endMarkingZoneGroup() { gcstats::AutoPhase ap(stats, gcstats::PHASE_SWEEP_MARK); /* * Mark any incoming black pointers from previously swept compartments * whose referents are not marked. This can occur when gray cells become * black by the action of UnmarkGray. */ MarkIncomingCrossCompartmentPointers(rt, BLACK); markWeakReferencesInCurrentGroup(gcstats::PHASE_SWEEP_MARK_WEAK); /* * Change state of current group to MarkGray to restrict marking to this * group. Note that there may be pointers to the atoms compartment, and * these will be marked through, as they are not marked with * MarkCrossCompartmentXXX. */ for (GCZoneGroupIter zone(rt); !zone.done(); zone.next()) { MOZ_ASSERT(zone->isGCMarkingBlack()); zone->setGCState(Zone::MarkGray); } marker.setMarkColorGray(); /* Mark incoming gray pointers from previously swept compartments. */ MarkIncomingCrossCompartmentPointers(rt, GRAY); /* Mark gray roots and mark transitively inside the current compartment group. */ markGrayReferencesInCurrentGroup(gcstats::PHASE_SWEEP_MARK_GRAY); markWeakReferencesInCurrentGroup(gcstats::PHASE_SWEEP_MARK_GRAY_WEAK); /* Restore marking state. */ for (GCZoneGroupIter zone(rt); !zone.done(); zone.next()) { MOZ_ASSERT(zone->isGCMarkingGray()); zone->setGCState(Zone::Mark); } MOZ_ASSERT(marker.isDrained()); marker.setMarkColorBlack(); } template <typename Derived> class GCSweepTask : public GCParallelTaskHelper<Derived> { GCSweepTask(const GCSweepTask&) = delete; protected: JSRuntime* runtime; public: explicit GCSweepTask(JSRuntime* rt) : runtime(rt) {} GCSweepTask(GCSweepTask&& other) : GCParallelTaskHelper<Derived>(mozilla::Move(other)), runtime(other.runtime) {} }; // Causes the given WeakCache to be swept when run. class SweepWeakCacheTask : public GCSweepTask<SweepWeakCacheTask> { JS::WeakCache<void*>& cache; SweepWeakCacheTask(const SweepWeakCacheTask&) = delete; public: SweepWeakCacheTask(JSRuntime* rt, JS::WeakCache<void*>& wc) : GCSweepTask(rt), cache(wc) {} SweepWeakCacheTask(SweepWeakCacheTask&& other) : GCSweepTask(mozilla::Move(other)), cache(other.cache) {} void run() { cache.sweep(); } }; #define MAKE_GC_SWEEP_TASK(name) \ class name : public GCSweepTask<name> { \ public: \ void run(); \ explicit name (JSRuntime* rt) : GCSweepTask(rt) {} \ } MAKE_GC_SWEEP_TASK(SweepAtomsTask); MAKE_GC_SWEEP_TASK(SweepCCWrappersTask); MAKE_GC_SWEEP_TASK(SweepBaseShapesTask); MAKE_GC_SWEEP_TASK(SweepInitialShapesTask); MAKE_GC_SWEEP_TASK(SweepObjectGroupsTask); MAKE_GC_SWEEP_TASK(SweepRegExpsTask); MAKE_GC_SWEEP_TASK(SweepMiscTask); #undef MAKE_GC_SWEEP_TASK /* virtual */ void SweepAtomsTask::run() { runtime->sweepAtoms(); for (CompartmentsIter comp(runtime, SkipAtoms); !comp.done(); comp.next()) comp->sweepVarNames(); } /* virtual */ void SweepCCWrappersTask::run() { for (GCCompartmentGroupIter c(runtime); !c.done(); c.next()) c->sweepCrossCompartmentWrappers(); } /* virtual */ void SweepObjectGroupsTask::run() { for (GCCompartmentGroupIter c(runtime); !c.done(); c.next()) c->objectGroups.sweep(runtime->defaultFreeOp()); } /* virtual */ void SweepRegExpsTask::run() { for (GCCompartmentGroupIter c(runtime); !c.done(); c.next()) c->sweepRegExps(); } /* virtual */ void SweepMiscTask::run() { for (GCCompartmentGroupIter c(runtime); !c.done(); c.next()) { c->sweepSavedStacks(); c->sweepSelfHostingScriptSource(); c->sweepNativeIterators(); } } void GCRuntime::startTask(GCParallelTask& task, gcstats::Phase phase, AutoLockHelperThreadState& locked) { if (!task.startWithLockHeld(locked)) { AutoUnlockHelperThreadState unlock(locked); gcstats::AutoPhase ap(stats, phase); task.runFromMainThread(rt); } } void GCRuntime::joinTask(GCParallelTask& task, gcstats::Phase phase, AutoLockHelperThreadState& locked) { gcstats::AutoPhase ap(stats, task, phase); task.joinWithLockHeld(locked); } using WeakCacheTaskVector = mozilla::Vector<SweepWeakCacheTask, 0, SystemAllocPolicy>; static void SweepWeakCachesFromMainThread(JSRuntime* rt) { for (GCZoneGroupIter zone(rt); !zone.done(); zone.next()) { for (JS::WeakCache<void*>* cache : zone->weakCaches_) { SweepWeakCacheTask task(rt, *cache); task.runFromMainThread(rt); } } } static WeakCacheTaskVector PrepareWeakCacheTasks(JSRuntime* rt) { WeakCacheTaskVector out; for (GCZoneGroupIter zone(rt); !zone.done(); zone.next()) { for (JS::WeakCache<void*>* cache : zone->weakCaches_) { if (!out.append(SweepWeakCacheTask(rt, *cache))) { SweepWeakCachesFromMainThread(rt); return WeakCacheTaskVector(); } } } return out; } void GCRuntime::beginSweepingZoneGroup(AutoLockForExclusiveAccess& lock) { /* * Begin sweeping the group of zones in gcCurrentZoneGroup, * performing actions that must be done before yielding to caller. */ bool sweepingAtoms = false; for (GCZoneGroupIter zone(rt); !zone.done(); zone.next()) { /* Set the GC state to sweeping. */ MOZ_ASSERT(zone->isGCMarking()); zone->setGCState(Zone::Sweep); /* Purge the ArenaLists before sweeping. */ zone->arenas.purge(); if (zone->isAtomsZone()) sweepingAtoms = true; if (rt->sweepZoneCallback) rt->sweepZoneCallback(zone); #ifdef DEBUG zone->gcLastZoneGroupIndex = zoneGroupIndex; #endif } FreeOp fop(rt); SweepAtomsTask sweepAtomsTask(rt); SweepCCWrappersTask sweepCCWrappersTask(rt); SweepObjectGroupsTask sweepObjectGroupsTask(rt); SweepRegExpsTask sweepRegExpsTask(rt); SweepMiscTask sweepMiscTask(rt); WeakCacheTaskVector sweepCacheTasks = PrepareWeakCacheTasks(rt); for (GCZoneGroupIter zone(rt); !zone.done(); zone.next()) { /* Clear all weakrefs that point to unmarked things. */ for (auto edge : zone->gcWeakRefs) { /* Edges may be present multiple times, so may already be nulled. */ if (*edge && IsAboutToBeFinalizedDuringSweep(**edge)) *edge = nullptr; } zone->gcWeakRefs.clear(); /* No need to look up any more weakmap keys from this zone group. */ AutoEnterOOMUnsafeRegion oomUnsafe; if (!zone->gcWeakKeys.clear()) oomUnsafe.crash("clearing weak keys in beginSweepingZoneGroup()"); } { gcstats::AutoPhase ap(stats, gcstats::PHASE_FINALIZE_START); callFinalizeCallbacks(&fop, JSFINALIZE_GROUP_START); { gcstats::AutoPhase ap2(stats, gcstats::PHASE_WEAK_ZONEGROUP_CALLBACK); callWeakPointerZoneGroupCallbacks(); } { gcstats::AutoPhase ap2(stats, gcstats::PHASE_WEAK_COMPARTMENT_CALLBACK); for (GCZoneGroupIter zone(rt); !zone.done(); zone.next()) { for (CompartmentsInZoneIter comp(zone); !comp.done(); comp.next()) callWeakPointerCompartmentCallbacks(comp); } } } if (sweepingAtoms) { AutoLockHelperThreadState helperLock; startTask(sweepAtomsTask, gcstats::PHASE_SWEEP_ATOMS, helperLock); } { gcstats::AutoPhase ap(stats, gcstats::PHASE_SWEEP_COMPARTMENTS); gcstats::AutoSCC scc(stats, zoneGroupIndex); { AutoLockHelperThreadState helperLock; startTask(sweepCCWrappersTask, gcstats::PHASE_SWEEP_CC_WRAPPER, helperLock); startTask(sweepObjectGroupsTask, gcstats::PHASE_SWEEP_TYPE_OBJECT, helperLock); startTask(sweepRegExpsTask, gcstats::PHASE_SWEEP_REGEXP, helperLock); startTask(sweepMiscTask, gcstats::PHASE_SWEEP_MISC, helperLock); for (auto& task : sweepCacheTasks) startTask(task, gcstats::PHASE_SWEEP_MISC, helperLock); } // The remainder of the of the tasks run in parallel on the main // thread until we join, below. { gcstats::AutoPhase ap(stats, gcstats::PHASE_SWEEP_MISC); // Cancel any active or pending off thread compilations. js::CancelOffThreadIonCompile(rt, JS::Zone::Sweep); for (GCCompartmentGroupIter c(rt); !c.done(); c.next()) { c->sweepGlobalObject(&fop); c->sweepDebugEnvironments(); c->sweepJitCompartment(&fop); c->sweepTemplateObjects(); } for (GCZoneGroupIter zone(rt); !zone.done(); zone.next()) zone->sweepWeakMaps(); // Bug 1071218: the following two methods have not yet been // refactored to work on a single zone-group at once. // Collect watch points associated with unreachable objects. WatchpointMap::sweepAll(rt); // Detach unreachable debuggers and global objects from each other. Debugger::sweepAll(&fop); // Sweep entries containing about-to-be-finalized JitCode and // update relocated TypeSet::Types inside the JitcodeGlobalTable. jit::JitRuntime::SweepJitcodeGlobalTable(rt); } { gcstats::AutoPhase apdc(stats, gcstats::PHASE_SWEEP_DISCARD_CODE); for (GCZoneGroupIter zone(rt); !zone.done(); zone.next()) zone->discardJitCode(&fop); } { gcstats::AutoPhase ap1(stats, gcstats::PHASE_SWEEP_TYPES); gcstats::AutoPhase ap2(stats, gcstats::PHASE_SWEEP_TYPES_BEGIN); for (GCZoneGroupIter zone(rt); !zone.done(); zone.next()) zone->beginSweepTypes(&fop, releaseObservedTypes && !zone->isPreservingCode()); } { gcstats::AutoPhase ap(stats, gcstats::PHASE_SWEEP_BREAKPOINT); for (GCZoneGroupIter zone(rt); !zone.done(); zone.next()) zone->sweepBreakpoints(&fop); } { gcstats::AutoPhase ap(stats, gcstats::PHASE_SWEEP_BREAKPOINT); for (GCZoneGroupIter zone(rt); !zone.done(); zone.next()) zone->sweepUniqueIds(&fop); } } if (sweepingAtoms) { gcstats::AutoPhase ap(stats, gcstats::PHASE_SWEEP_SYMBOL_REGISTRY); rt->symbolRegistry(lock).sweep(); } // Rejoin our off-main-thread tasks. if (sweepingAtoms) { AutoLockHelperThreadState helperLock; joinTask(sweepAtomsTask, gcstats::PHASE_SWEEP_ATOMS, helperLock); } { gcstats::AutoPhase ap(stats, gcstats::PHASE_SWEEP_COMPARTMENTS); gcstats::AutoSCC scc(stats, zoneGroupIndex); AutoLockHelperThreadState helperLock; joinTask(sweepCCWrappersTask, gcstats::PHASE_SWEEP_CC_WRAPPER, helperLock); joinTask(sweepObjectGroupsTask, gcstats::PHASE_SWEEP_TYPE_OBJECT, helperLock); joinTask(sweepRegExpsTask, gcstats::PHASE_SWEEP_REGEXP, helperLock); joinTask(sweepMiscTask, gcstats::PHASE_SWEEP_MISC, helperLock); for (auto& task : sweepCacheTasks) joinTask(task, gcstats::PHASE_SWEEP_MISC, helperLock); } /* * Queue all GC things in all zones for sweeping, either in the * foreground or on the background thread. * * Note that order is important here for the background case. * * Objects are finalized immediately but this may change in the future. */ for (GCZoneGroupIter zone(rt); !zone.done(); zone.next()) { gcstats::AutoSCC scc(stats, zoneGroupIndex); zone->arenas.queueForegroundObjectsForSweep(&fop); } for (GCZoneGroupIter zone(rt); !zone.done(); zone.next()) { gcstats::AutoSCC scc(stats, zoneGroupIndex); for (unsigned i = 0; i < ArrayLength(IncrementalFinalizePhases); ++i) zone->arenas.queueForForegroundSweep(&fop, IncrementalFinalizePhases[i]); } for (GCZoneGroupIter zone(rt); !zone.done(); zone.next()) { gcstats::AutoSCC scc(stats, zoneGroupIndex); for (unsigned i = 0; i < ArrayLength(BackgroundFinalizePhases); ++i) zone->arenas.queueForBackgroundSweep(&fop, BackgroundFinalizePhases[i]); } for (GCZoneGroupIter zone(rt); !zone.done(); zone.next()) { gcstats::AutoSCC scc(stats, zoneGroupIndex); zone->arenas.queueForegroundThingsForSweep(&fop); } sweepingTypes = true; finalizePhase = 0; sweepZone = currentZoneGroup; sweepKind = AllocKind::FIRST; { gcstats::AutoPhase ap(stats, gcstats::PHASE_FINALIZE_END); callFinalizeCallbacks(&fop, JSFINALIZE_GROUP_END); } } void GCRuntime::endSweepingZoneGroup() { /* Update the GC state for zones we have swept. */ for (GCZoneGroupIter zone(rt); !zone.done(); zone.next()) { MOZ_ASSERT(zone->isGCSweeping()); AutoLockGC lock(rt); zone->setGCState(Zone::Finished); zone->threshold.updateAfterGC(zone->usage.gcBytes(), invocationKind, tunables, schedulingState, lock); } /* Start background thread to sweep zones if required. */ ZoneList zones; for (GCZoneGroupIter zone(rt); !zone.done(); zone.next()) zones.append(zone); if (sweepOnBackgroundThread) queueZonesForBackgroundSweep(zones); else sweepBackgroundThings(zones, blocksToFreeAfterSweeping); /* Reset the list of arenas marked as being allocated during sweep phase. */ while (Arena* arena = arenasAllocatedDuringSweep) { arenasAllocatedDuringSweep = arena->getNextAllocDuringSweep(); arena->unsetAllocDuringSweep(); } } void GCRuntime::beginSweepPhase(bool destroyingRuntime, AutoLockForExclusiveAccess& lock) { /* * Sweep phase. * * Finalize as we sweep, outside of lock but with rt->isHeapBusy() * true so that any attempt to allocate a GC-thing from a finalizer will * fail, rather than nest badly and leave the unmarked newborn to be swept. */ MOZ_ASSERT(!abortSweepAfterCurrentGroup); AutoSetThreadIsSweeping threadIsSweeping; releaseHeldRelocatedArenas(); gcstats::AutoPhase ap(stats, gcstats::PHASE_SWEEP); sweepOnBackgroundThread = !destroyingRuntime && !TraceEnabled() && CanUseExtraThreads(); releaseObservedTypes = shouldReleaseObservedTypes(); AssertNoWrappersInGrayList(rt); DropStringWrappers(rt); findZoneGroups(lock); endMarkingZoneGroup(); beginSweepingZoneGroup(lock); } bool ArenaLists::foregroundFinalize(FreeOp* fop, AllocKind thingKind, SliceBudget& sliceBudget, SortedArenaList& sweepList) { if (!arenaListsToSweep[thingKind] && incrementalSweptArenas.isEmpty()) return true; if (!FinalizeArenas(fop, &arenaListsToSweep[thingKind], sweepList, thingKind, sliceBudget, RELEASE_ARENAS)) { incrementalSweptArenaKind = thingKind; incrementalSweptArenas = sweepList.toArenaList(); return false; } // Clear any previous incremental sweep state we may have saved. incrementalSweptArenas.clear(); // Join |arenaLists[thingKind]| and |sweepList| into a single list. ArenaList finalized = sweepList.toArenaList(); arenaLists[thingKind] = finalized.insertListWithCursorAtEnd(arenaLists[thingKind]); return true; } GCRuntime::IncrementalProgress GCRuntime::drainMarkStack(SliceBudget& sliceBudget, gcstats::Phase phase) { /* Run a marking slice and return whether the stack is now empty. */ gcstats::AutoPhase ap(stats, phase); return marker.drainMarkStack(sliceBudget) ? Finished : NotFinished; } static void SweepThing(Shape* shape) { if (!shape->isMarked()) shape->sweep(); } static void SweepThing(JSScript* script, AutoClearTypeInferenceStateOnOOM* oom) { script->maybeSweepTypes(oom); } static void SweepThing(ObjectGroup* group, AutoClearTypeInferenceStateOnOOM* oom) { group->maybeSweep(oom); } template <typename T, typename... Args> static bool SweepArenaList(Arena** arenasToSweep, SliceBudget& sliceBudget, Args... args) { while (Arena* arena = *arenasToSweep) { for (ArenaCellIterUnderGC i(arena); !i.done(); i.next()) SweepThing(i.get<T>(), args...); *arenasToSweep = (*arenasToSweep)->next; AllocKind kind = MapTypeToFinalizeKind<T>::kind; sliceBudget.step(Arena::thingsPerArena(kind)); if (sliceBudget.isOverBudget()) return false; } return true; } GCRuntime::IncrementalProgress GCRuntime::sweepPhase(SliceBudget& sliceBudget, AutoLockForExclusiveAccess& lock) { AutoSetThreadIsSweeping threadIsSweeping; gcstats::AutoPhase ap(stats, gcstats::PHASE_SWEEP); FreeOp fop(rt); if (drainMarkStack(sliceBudget, gcstats::PHASE_SWEEP_MARK) == NotFinished) return NotFinished; for (;;) { // Sweep dead type information stored in scripts and object groups, but // don't finalize them yet. We have to sweep dead information from both // live and dead scripts and object groups, so that no dead references // remain in them. Type inference can end up crawling these zones // again, such as for TypeCompartment::markSetsUnknown, and if this // happens after sweeping for the zone group finishes we won't be able // to determine which things in the zone are live. if (sweepingTypes) { gcstats::AutoPhase ap1(stats, gcstats::PHASE_SWEEP_COMPARTMENTS); gcstats::AutoPhase ap2(stats, gcstats::PHASE_SWEEP_TYPES); for (; sweepZone; sweepZone = sweepZone->nextNodeInGroup()) { ArenaLists& al = sweepZone->arenas; AutoClearTypeInferenceStateOnOOM oom(sweepZone); if (!SweepArenaList<JSScript>(&al.gcScriptArenasToUpdate, sliceBudget, &oom)) return NotFinished; if (!SweepArenaList<ObjectGroup>( &al.gcObjectGroupArenasToUpdate, sliceBudget, &oom)) { return NotFinished; } // Finish sweeping type information in the zone. { gcstats::AutoPhase ap(stats, gcstats::PHASE_SWEEP_TYPES_END); sweepZone->types.endSweep(rt); } // Foreground finalized objects have already been finalized, // and now their arenas can be reclaimed by freeing empty ones // and making non-empty ones available for allocation. al.mergeForegroundSweptObjectArenas(); } sweepZone = currentZoneGroup; sweepingTypes = false; } /* Finalize foreground finalized things. */ for (; finalizePhase < ArrayLength(IncrementalFinalizePhases) ; ++finalizePhase) { gcstats::AutoPhase ap(stats, IncrementalFinalizePhases[finalizePhase].statsPhase); for (; sweepZone; sweepZone = sweepZone->nextNodeInGroup()) { Zone* zone = sweepZone; for (auto kind : SomeAllocKinds(sweepKind, AllocKind::LIMIT)) { if (!IncrementalFinalizePhases[finalizePhase].kinds.contains(kind)) continue; /* Set the number of things per arena for this AllocKind. */ size_t thingsPerArena = Arena::thingsPerArena(kind); incrementalSweepList.setThingsPerArena(thingsPerArena); if (!zone->arenas.foregroundFinalize(&fop, kind, sliceBudget, incrementalSweepList)) { sweepKind = kind; return NotFinished; } /* Reset the slots of the sweep list that we used. */ incrementalSweepList.reset(thingsPerArena); } sweepKind = AllocKind::FIRST; } sweepZone = currentZoneGroup; } /* Remove dead shapes from the shape tree, but don't finalize them yet. */ { gcstats::AutoPhase ap(stats, gcstats::PHASE_SWEEP_SHAPE); for (; sweepZone; sweepZone = sweepZone->nextNodeInGroup()) { ArenaLists& al = sweepZone->arenas; if (!SweepArenaList<Shape>(&al.gcShapeArenasToUpdate, sliceBudget)) return NotFinished; if (!SweepArenaList<AccessorShape>(&al.gcAccessorShapeArenasToUpdate, sliceBudget)) return NotFinished; } } endSweepingZoneGroup(); getNextZoneGroup(); if (!currentZoneGroup) return Finished; endMarkingZoneGroup(); beginSweepingZoneGroup(lock); } } void GCRuntime::endSweepPhase(bool destroyingRuntime, AutoLockForExclusiveAccess& lock) { AutoSetThreadIsSweeping threadIsSweeping; gcstats::AutoPhase ap(stats, gcstats::PHASE_SWEEP); FreeOp fop(rt); MOZ_ASSERT_IF(destroyingRuntime, !sweepOnBackgroundThread); /* * Recalculate whether GC was full or not as this may have changed due to * newly created zones. Can only change from full to not full. */ if (isFull) { for (ZonesIter zone(rt, WithAtoms); !zone.done(); zone.next()) { if (!zone->isCollecting()) { isFull = false; break; } } } { gcstats::AutoPhase ap(stats, gcstats::PHASE_DESTROY); /* * Sweep script filenames after sweeping functions in the generic loop * above. In this way when a scripted function's finalizer destroys the * script and calls rt->destroyScriptHook, the hook can still access the * script's filename. See bug 323267. */ SweepScriptData(rt, lock); /* Clear out any small pools that we're hanging on to. */ if (jit::JitRuntime* jitRuntime = rt->jitRuntime()) { jitRuntime->execAlloc().purge(); jitRuntime->backedgeExecAlloc().purge(); } } { gcstats::AutoPhase ap(stats, gcstats::PHASE_FINALIZE_END); callFinalizeCallbacks(&fop, JSFINALIZE_COLLECTION_END); /* If we finished a full GC, then the gray bits are correct. */ if (isFull) rt->setGCGrayBitsValid(true); } #ifdef DEBUG for (ZonesIter zone(rt, WithAtoms); !zone.done(); zone.next()) { for (auto i : AllAllocKinds()) { MOZ_ASSERT_IF(!IsBackgroundFinalized(i) || !sweepOnBackgroundThread, !zone->arenas.arenaListsToSweep[i]); } } #endif AssertNoWrappersInGrayList(rt); } void GCRuntime::beginCompactPhase() { MOZ_ASSERT(!isBackgroundSweeping()); gcstats::AutoPhase ap(stats, gcstats::PHASE_COMPACT); MOZ_ASSERT(zonesToMaybeCompact.isEmpty()); for (GCZonesIter zone(rt); !zone.done(); zone.next()) { if (CanRelocateZone(zone)) zonesToMaybeCompact.append(zone); } MOZ_ASSERT(!relocatedArenasToRelease); startedCompacting = true; } GCRuntime::IncrementalProgress GCRuntime::compactPhase(JS::gcreason::Reason reason, SliceBudget& sliceBudget, AutoLockForExclusiveAccess& lock) { MOZ_ASSERT(rt->gc.nursery.isEmpty()); assertBackgroundSweepingFinished(); MOZ_ASSERT(startedCompacting); gcstats::AutoPhase ap(stats, gcstats::PHASE_COMPACT); Arena* relocatedArenas = nullptr; while (!zonesToMaybeCompact.isEmpty()) { // TODO: JSScripts can move. If the sampler interrupts the GC in the // middle of relocating an arena, invalid JSScript pointers may be // accessed. Suppress all sampling until a finer-grained solution can be // found. See bug 1295775. AutoSuppressProfilerSampling suppressSampling(rt); Zone* zone = zonesToMaybeCompact.front(); MOZ_ASSERT(zone->isGCFinished()); zone->setGCState(Zone::Compact); if (relocateArenas(zone, reason, relocatedArenas, sliceBudget)) updatePointersToRelocatedCells(zone, lock); zone->setGCState(Zone::Finished); zonesToMaybeCompact.removeFront(); if (sliceBudget.isOverBudget()) break; } if (ShouldProtectRelocatedArenas(reason)) protectAndHoldArenas(relocatedArenas); else releaseRelocatedArenas(relocatedArenas); // Clear caches that can contain cell pointers. JSContext* cx = rt->contextFromMainThread(); cx->caches.newObjectCache.purge(); cx->caches.nativeIterCache.purge(); if (cx->caches.evalCache.initialized()) cx->caches.evalCache.clear(); #ifdef DEBUG CheckHashTablesAfterMovingGC(rt); #endif return zonesToMaybeCompact.isEmpty() ? Finished : NotFinished; } void GCRuntime::endCompactPhase(JS::gcreason::Reason reason) { startedCompacting = false; } void GCRuntime::finishCollection(JS::gcreason::Reason reason) { assertBackgroundSweepingFinished(); MOZ_ASSERT(marker.isDrained()); marker.stop(); clearBufferedGrayRoots(); MemProfiler::SweepTenured(rt); uint64_t currentTime = PRMJ_Now(); schedulingState.updateHighFrequencyMode(lastGCTime, currentTime, tunables); for (ZonesIter zone(rt, WithAtoms); !zone.done(); zone.next()) { if (zone->isCollecting()) { MOZ_ASSERT(zone->isGCFinished()); zone->setGCState(Zone::NoGC); zone->active = false; } MOZ_ASSERT(!zone->isCollecting()); MOZ_ASSERT(!zone->wasGCStarted()); } MOZ_ASSERT(zonesToMaybeCompact.isEmpty()); lastGCTime = currentTime; } static const char* HeapStateToLabel(JS::HeapState heapState) { switch (heapState) { case JS::HeapState::MinorCollecting: return "js::Nursery::collect"; case JS::HeapState::MajorCollecting: return "js::GCRuntime::collect"; case JS::HeapState::Tracing: return "JS_IterateCompartments"; case JS::HeapState::Idle: case JS::HeapState::CycleCollecting: MOZ_CRASH("Should never have an Idle or CC heap state when pushing GC pseudo frames!"); } MOZ_ASSERT_UNREACHABLE("Should have exhausted every JS::HeapState variant!"); return nullptr; } /* Start a new heap session. */ AutoTraceSession::AutoTraceSession(JSRuntime* rt, JS::HeapState heapState) : lock(rt), runtime(rt), prevState(rt->heapState()), pseudoFrame(rt, HeapStateToLabel(heapState), ProfileEntry::Category::GC) { MOZ_ASSERT(prevState == JS::HeapState::Idle); MOZ_ASSERT(heapState != JS::HeapState::Idle); MOZ_ASSERT_IF(heapState == JS::HeapState::MajorCollecting, rt->gc.nursery.isEmpty()); rt->setHeapState(heapState); } AutoTraceSession::~AutoTraceSession() { MOZ_ASSERT(runtime->isHeapBusy()); runtime->setHeapState(prevState); } void GCRuntime::resetIncrementalGC(gc::AbortReason reason, AutoLockForExclusiveAccess& lock) { MOZ_ASSERT(reason != gc::AbortReason::None); switch (incrementalState) { case State::NotActive: return; case State::MarkRoots: MOZ_CRASH("resetIncrementalGC did not expect MarkRoots state"); break; case State::Mark: { /* Cancel any ongoing marking. */ marker.reset(); marker.stop(); clearBufferedGrayRoots(); for (GCCompartmentsIter c(rt); !c.done(); c.next()) ResetGrayList(c); for (GCZonesIter zone(rt); !zone.done(); zone.next()) { MOZ_ASSERT(zone->isGCMarking()); zone->setNeedsIncrementalBarrier(false, Zone::UpdateJit); zone->setGCState(Zone::NoGC); } blocksToFreeAfterSweeping.freeAll(); incrementalState = State::NotActive; MOZ_ASSERT(!marker.shouldCheckCompartments()); break; } case State::Sweep: { marker.reset(); for (CompartmentsIter c(rt, SkipAtoms); !c.done(); c.next()) c->scheduledForDestruction = false; /* Finish sweeping the current zone group, then abort. */ abortSweepAfterCurrentGroup = true; /* Don't perform any compaction after sweeping. */ bool wasCompacting = isCompacting; isCompacting = false; auto unlimited = SliceBudget::unlimited(); incrementalCollectSlice(unlimited, JS::gcreason::RESET, lock); isCompacting = wasCompacting; { gcstats::AutoPhase ap(stats, gcstats::PHASE_WAIT_BACKGROUND_THREAD); rt->gc.waitBackgroundSweepOrAllocEnd(); } break; } case State::Finalize: { { gcstats::AutoPhase ap(stats, gcstats::PHASE_WAIT_BACKGROUND_THREAD); rt->gc.waitBackgroundSweepOrAllocEnd(); } bool wasCompacting = isCompacting; isCompacting = false; auto unlimited = SliceBudget::unlimited(); incrementalCollectSlice(unlimited, JS::gcreason::RESET, lock); isCompacting = wasCompacting; break; } case State::Compact: { bool wasCompacting = isCompacting; isCompacting = true; startedCompacting = true; zonesToMaybeCompact.clear(); auto unlimited = SliceBudget::unlimited(); incrementalCollectSlice(unlimited, JS::gcreason::RESET, lock); isCompacting = wasCompacting; break; } case State::Decommit: { auto unlimited = SliceBudget::unlimited(); incrementalCollectSlice(unlimited, JS::gcreason::RESET, lock); break; } } stats.reset(reason); #ifdef DEBUG assertBackgroundSweepingFinished(); for (ZonesIter zone(rt, WithAtoms); !zone.done(); zone.next()) { MOZ_ASSERT(!zone->isCollecting()); MOZ_ASSERT(!zone->needsIncrementalBarrier()); MOZ_ASSERT(!zone->isOnList()); } MOZ_ASSERT(zonesToMaybeCompact.isEmpty()); MOZ_ASSERT(incrementalState == State::NotActive); #endif } namespace { class AutoGCSlice { public: explicit AutoGCSlice(JSRuntime* rt); ~AutoGCSlice(); private: JSRuntime* runtime; AutoSetThreadIsPerformingGC performingGC; }; } /* anonymous namespace */ AutoGCSlice::AutoGCSlice(JSRuntime* rt) : runtime(rt) { /* * During incremental GC, the compartment's active flag determines whether * there are stack frames active for any of its scripts. Normally this flag * is set at the beginning of the mark phase. During incremental GC, we also * set it at the start of every phase. */ for (ActivationIterator iter(rt); !iter.done(); ++iter) iter->compartment()->zone()->active = true; for (GCZonesIter zone(rt); !zone.done(); zone.next()) { /* * Clear needsIncrementalBarrier early so we don't do any write * barriers during GC. We don't need to update the Ion barriers (which * is expensive) because Ion code doesn't run during GC. If need be, * we'll update the Ion barriers in ~AutoGCSlice. */ if (zone->isGCMarking()) { MOZ_ASSERT(zone->needsIncrementalBarrier()); zone->setNeedsIncrementalBarrier(false, Zone::DontUpdateJit); } else { MOZ_ASSERT(!zone->needsIncrementalBarrier()); } } } AutoGCSlice::~AutoGCSlice() { /* We can't use GCZonesIter if this is the end of the last slice. */ for (ZonesIter zone(runtime, WithAtoms); !zone.done(); zone.next()) { if (zone->isGCMarking()) { zone->setNeedsIncrementalBarrier(true, Zone::UpdateJit); zone->arenas.purge(); } else { zone->setNeedsIncrementalBarrier(false, Zone::UpdateJit); } } } static bool IsShutdownGC(JS::gcreason::Reason reason) { return reason == JS::gcreason::SHUTDOWN_CC || reason == JS::gcreason::DESTROY_RUNTIME; } static bool ShouldCleanUpEverything(JS::gcreason::Reason reason, JSGCInvocationKind gckind) { // During shutdown, we must clean everything up, for the sake of leak // detection. When a runtime has no contexts, or we're doing a GC before a // shutdown CC, those are strong indications that we're shutting down. return IsShutdownGC(reason) || gckind == GC_SHRINK; } void GCRuntime::incrementalCollectSlice(SliceBudget& budget, JS::gcreason::Reason reason, AutoLockForExclusiveAccess& lock) { AutoGCSlice slice(rt); bool destroyingRuntime = (reason == JS::gcreason::DESTROY_RUNTIME); gc::State initialState = incrementalState; MOZ_ASSERT_IF(isIncrementalGCInProgress(), isIncremental); isIncremental = !budget.isUnlimited(); switch (incrementalState) { case State::NotActive: initialReason = reason; cleanUpEverything = ShouldCleanUpEverything(reason, invocationKind); isCompacting = shouldCompact(); lastMarkSlice = false; incrementalState = State::MarkRoots; MOZ_FALLTHROUGH; case State::MarkRoots: if (!beginMarkPhase(reason, lock)) { incrementalState = State::NotActive; return; } incrementalState = State::Mark; MOZ_FALLTHROUGH; case State::Mark: AutoGCRooter::traceAllWrappers(&marker); /* If we needed delayed marking for gray roots, then collect until done. */ if (!hasBufferedGrayRoots()) { budget.makeUnlimited(); isIncremental = false; } if (drainMarkStack(budget, gcstats::PHASE_MARK) == NotFinished) break; MOZ_ASSERT(marker.isDrained()); /* * In incremental GCs where we have already performed more than once * slice we yield after marking with the aim of starting the sweep in * the next slice, since the first slice of sweeping can be expensive. * * This is modified by the various zeal modes. We don't yield in * IncrementalRootsThenFinish mode and we always yield in * IncrementalMarkAllThenFinish mode. * * We will need to mark anything new on the stack when we resume, so * we stay in Mark state. */ if (!lastMarkSlice && isIncremental && initialState == State::Mark) { lastMarkSlice = true; break; } incrementalState = State::Sweep; /* * This runs to completion, but we don't continue if the budget is * now exhasted. */ beginSweepPhase(destroyingRuntime, lock); if (budget.isOverBudget()) break; MOZ_FALLTHROUGH; case State::Sweep: if (sweepPhase(budget, lock) == NotFinished) break; endSweepPhase(destroyingRuntime, lock); incrementalState = State::Finalize; MOZ_FALLTHROUGH; case State::Finalize: { gcstats::AutoPhase ap(stats, gcstats::PHASE_WAIT_BACKGROUND_THREAD); // Yield until background finalization is done. if (isIncremental) { // Poll for end of background sweeping AutoLockGC lock(rt); if (isBackgroundSweeping()) break; } else { waitBackgroundSweepEnd(); } } { // Re-sweep the zones list, now that background finalization is // finished to actually remove and free dead zones. gcstats::AutoPhase ap1(stats, gcstats::PHASE_SWEEP); gcstats::AutoPhase ap2(stats, gcstats::PHASE_DESTROY); AutoSetThreadIsSweeping threadIsSweeping; FreeOp fop(rt); sweepZones(&fop, destroyingRuntime); } MOZ_ASSERT(!startedCompacting); incrementalState = State::Compact; // Always yield before compacting since it is not incremental. if (isCompacting && isIncremental) break; MOZ_FALLTHROUGH; case State::Compact: if (isCompacting) { if (!startedCompacting) beginCompactPhase(); if (compactPhase(reason, budget, lock) == NotFinished) break; endCompactPhase(reason); } startDecommit(); incrementalState = State::Decommit; MOZ_FALLTHROUGH; case State::Decommit: { gcstats::AutoPhase ap(stats, gcstats::PHASE_WAIT_BACKGROUND_THREAD); // Yield until background decommit is done. if (isIncremental && decommitTask.isRunning()) break; decommitTask.join(); } finishCollection(reason); incrementalState = State::NotActive; break; } } gc::AbortReason gc::IsIncrementalGCUnsafe(JSRuntime* rt) { MOZ_ASSERT(!rt->mainThread.suppressGC); if (rt->keepAtoms()) return gc::AbortReason::KeepAtomsSet; if (!rt->gc.isIncrementalGCAllowed()) return gc::AbortReason::IncrementalDisabled; return gc::AbortReason::None; } void GCRuntime::budgetIncrementalGC(JS::gcreason::Reason reason, SliceBudget& budget, AutoLockForExclusiveAccess& lock) { AbortReason unsafeReason = IsIncrementalGCUnsafe(rt); if (unsafeReason == AbortReason::None) { if (reason == JS::gcreason::COMPARTMENT_REVIVED) unsafeReason = gc::AbortReason::CompartmentRevived; else if (mode != JSGC_MODE_INCREMENTAL) unsafeReason = gc::AbortReason::ModeChange; } if (unsafeReason != AbortReason::None) { resetIncrementalGC(unsafeReason, lock); budget.makeUnlimited(); stats.nonincremental(unsafeReason); return; } if (isTooMuchMalloc()) { budget.makeUnlimited(); stats.nonincremental(AbortReason::MallocBytesTrigger); } bool reset = false; for (ZonesIter zone(rt, WithAtoms); !zone.done(); zone.next()) { if (zone->usage.gcBytes() >= zone->threshold.gcTriggerBytes()) { budget.makeUnlimited(); stats.nonincremental(AbortReason::GCBytesTrigger); } if (isIncrementalGCInProgress() && zone->isGCScheduled() != zone->wasGCStarted()) reset = true; if (zone->isTooMuchMalloc()) { budget.makeUnlimited(); stats.nonincremental(AbortReason::MallocBytesTrigger); } } if (reset) resetIncrementalGC(AbortReason::ZoneChange, lock); } namespace { class AutoScheduleZonesForGC { JSRuntime* rt_; public: explicit AutoScheduleZonesForGC(JSRuntime* rt) : rt_(rt) { for (ZonesIter zone(rt_, WithAtoms); !zone.done(); zone.next()) { if (rt->gc.gcMode() == JSGC_MODE_GLOBAL) zone->scheduleGC(); /* This is a heuristic to avoid resets. */ if (rt->gc.isIncrementalGCInProgress() && zone->needsIncrementalBarrier()) zone->scheduleGC(); /* This is a heuristic to reduce the total number of collections. */ if (zone->usage.gcBytes() >= zone->threshold.allocTrigger(rt->gc.schedulingState.inHighFrequencyGCMode())) { zone->scheduleGC(); } } } ~AutoScheduleZonesForGC() { for (ZonesIter zone(rt_, WithAtoms); !zone.done(); zone.next()) zone->unscheduleGC(); } }; /* * An invariant of our GC/CC interaction is that there must not ever be any * black to gray edges in the system. It is possible to violate this with * simple compartmental GC. For example, in GC[n], we collect in both * compartmentA and compartmentB, and mark both sides of the cross-compartment * edge gray. Later in GC[n+1], we only collect compartmentA, but this time * mark it black. Now we are violating the invariants and must fix it somehow. * * To prevent this situation, we explicitly detect the black->gray state when * marking cross-compartment edges -- see ShouldMarkCrossCompartment -- adding * each violating edges to foundBlackGrayEdges. After we leave the trace * session for each GC slice, we "ExposeToActiveJS" on each of these edges * (which we cannot do safely from the guts of the GC). */ class AutoExposeLiveCrossZoneEdges { BlackGrayEdgeVector* edges; public: explicit AutoExposeLiveCrossZoneEdges(BlackGrayEdgeVector* edgesPtr) : edges(edgesPtr) { MOZ_ASSERT(edges->empty()); } ~AutoExposeLiveCrossZoneEdges() { for (auto& target : *edges) { MOZ_ASSERT(target); MOZ_ASSERT(!target->zone()->isCollecting()); UnmarkGrayCellRecursively(target, target->getTraceKind()); } edges->clear(); } }; } /* anonymous namespace */ /* * Run one GC "cycle" (either a slice of incremental GC or an entire * non-incremental GC. We disable inlining to ensure that the bottom of the * stack with possible GC roots recorded in MarkRuntime excludes any pointers we * use during the marking implementation. * * Returns true if we "reset" an existing incremental GC, which would force us * to run another cycle. */ MOZ_NEVER_INLINE bool GCRuntime::gcCycle(bool nonincrementalByAPI, SliceBudget& budget, JS::gcreason::Reason reason) { // Note that the following is allowed to re-enter GC in the finalizer. AutoNotifyGCActivity notify(*this); gcstats::AutoGCSlice agc(stats, scanZonesBeforeGC(), invocationKind, budget, reason); AutoExposeLiveCrossZoneEdges aelcze(&foundBlackGrayEdges); evictNursery(reason); AutoTraceSession session(rt, JS::HeapState::MajorCollecting); majorGCTriggerReason = JS::gcreason::NO_REASON; interFrameGC = true; number++; if (!isIncrementalGCInProgress()) incMajorGcNumber(); // It's ok if threads other than the main thread have suppressGC set, as // they are operating on zones which will not be collected from here. MOZ_ASSERT(!rt->mainThread.suppressGC); // Assert if this is a GC unsafe region. verifyIsSafeToGC(); { gcstats::AutoPhase ap(stats, gcstats::PHASE_WAIT_BACKGROUND_THREAD); // Background finalization and decommit are finished by defininition // before we can start a new GC session. if (!isIncrementalGCInProgress()) { assertBackgroundSweepingFinished(); MOZ_ASSERT(!decommitTask.isRunning()); } // We must also wait for background allocation to finish so we can // avoid taking the GC lock when manipulating the chunks during the GC. // The background alloc task can run between slices, so we must wait // for it at the start of every slice. allocTask.cancel(GCParallelTask::CancelAndWait); } State prevState = incrementalState; if (nonincrementalByAPI) { // Reset any in progress incremental GC if this was triggered via the // API. This isn't required for correctness, but sometimes during tests // the caller expects this GC to collect certain objects, and we need // to make sure to collect everything possible. if (reason != JS::gcreason::ALLOC_TRIGGER) resetIncrementalGC(gc::AbortReason::NonIncrementalRequested, session.lock); stats.nonincremental(gc::AbortReason::NonIncrementalRequested); budget.makeUnlimited(); } else { budgetIncrementalGC(reason, budget, session.lock); } /* The GC was reset, so we need a do-over. */ if (prevState != State::NotActive && !isIncrementalGCInProgress()) return true; TraceMajorGCStart(); incrementalCollectSlice(budget, reason, session.lock); chunkAllocationSinceLastGC = false; /* Clear gcMallocBytes for all zones. */ for (ZonesIter zone(rt, WithAtoms); !zone.done(); zone.next()) zone->resetGCMallocBytes(); resetMallocBytes(); TraceMajorGCEnd(); return false; } gcstats::ZoneGCStats GCRuntime::scanZonesBeforeGC() { gcstats::ZoneGCStats zoneStats; for (ZonesIter zone(rt, WithAtoms); !zone.done(); zone.next()) { zoneStats.zoneCount++; if (zone->isGCScheduled()) { zoneStats.collectedZoneCount++; zoneStats.collectedCompartmentCount += zone->compartments.length(); } } for (CompartmentsIter c(rt, WithAtoms); !c.done(); c.next()) zoneStats.compartmentCount++; return zoneStats; } // The GC can only clean up scheduledForDestruction compartments that were // marked live by a barrier (e.g. by RemapWrappers from a navigation event). // It is also common to have compartments held live because they are part of a // cycle in gecko, e.g. involving the HTMLDocument wrapper. In this case, we // need to run the CycleCollector in order to remove these edges before the // compartment can be freed. void GCRuntime::maybeDoCycleCollection() { const static double ExcessiveGrayCompartments = 0.8; const static size_t LimitGrayCompartments = 200; size_t compartmentsTotal = 0; size_t compartmentsGray = 0; for (CompartmentsIter c(rt, SkipAtoms); !c.done(); c.next()) { ++compartmentsTotal; GlobalObject* global = c->unsafeUnbarrieredMaybeGlobal(); if (global && global->asTenured().isMarked(GRAY)) ++compartmentsGray; } double grayFraction = double(compartmentsGray) / double(compartmentsTotal); if (grayFraction > ExcessiveGrayCompartments || compartmentsGray > LimitGrayCompartments) callDoCycleCollectionCallback(rt->contextFromMainThread()); } void GCRuntime::checkCanCallAPI() { MOZ_RELEASE_ASSERT(CurrentThreadCanAccessRuntime(rt)); /* If we attempt to invoke the GC while we are running in the GC, assert. */ MOZ_RELEASE_ASSERT(!rt->isHeapBusy()); MOZ_ASSERT(isAllocAllowed()); } bool GCRuntime::checkIfGCAllowedInCurrentState(JS::gcreason::Reason reason) { if (rt->mainThread.suppressGC) return false; // Only allow shutdown GCs when we're destroying the runtime. This keeps // the GC callback from triggering a nested GC and resetting global state. if (rt->isBeingDestroyed() && !IsShutdownGC(reason)) return false; return true; } bool GCRuntime::shouldRepeatForDeadZone(JS::gcreason::Reason reason) { MOZ_ASSERT_IF(reason == JS::gcreason::COMPARTMENT_REVIVED, !isIncremental); if (!isIncremental || isIncrementalGCInProgress()) return false; for (CompartmentsIter c(rt, SkipAtoms); !c.done(); c.next()) { if (c->scheduledForDestruction) return true; } return false; } void GCRuntime::collect(bool nonincrementalByAPI, SliceBudget budget, JS::gcreason::Reason reason) { // Checks run for each request, even if we do not actually GC. checkCanCallAPI(); // Check if we are allowed to GC at this time before proceeding. if (!checkIfGCAllowedInCurrentState(reason)) return; AutoTraceLog logGC(TraceLoggerForMainThread(rt), TraceLogger_GC); AutoEnqueuePendingParseTasksAfterGC aept(*this); AutoScheduleZonesForGC asz(rt); bool repeat = false; do { poked = false; bool wasReset = gcCycle(nonincrementalByAPI, budget, reason); bool repeatForDeadZone = false; if (poked && cleanUpEverything) { /* Need to re-schedule all zones for GC. */ JS::PrepareForFullGC(rt->contextFromMainThread()); } else if (shouldRepeatForDeadZone(reason) && !wasReset) { /* * This code makes an extra effort to collect compartments that we * thought were dead at the start of the GC. See the large comment * in beginMarkPhase. */ repeatForDeadZone = true; reason = JS::gcreason::COMPARTMENT_REVIVED; } /* * If we reset an existing GC, we need to start a new one. Also, we * repeat GCs that happen during shutdown (the gcShouldCleanUpEverything * case) until we can be sure that no additional garbage is created * (which typically happens if roots are dropped during finalizers). */ repeat = (poked && cleanUpEverything) || wasReset || repeatForDeadZone; } while (repeat); if (reason == JS::gcreason::COMPARTMENT_REVIVED) maybeDoCycleCollection(); } js::AutoEnqueuePendingParseTasksAfterGC::~AutoEnqueuePendingParseTasksAfterGC() { if (!OffThreadParsingMustWaitForGC(gc_.rt)) EnqueuePendingParseTasksAfterGC(gc_.rt); } SliceBudget GCRuntime::defaultBudget(JS::gcreason::Reason reason, int64_t millis) { if (millis == 0) { if (reason == JS::gcreason::ALLOC_TRIGGER) millis = defaultSliceBudget(); else if (schedulingState.inHighFrequencyGCMode() && tunables.isDynamicMarkSliceEnabled()) millis = defaultSliceBudget() * IGC_MARK_SLICE_MULTIPLIER; else millis = defaultSliceBudget(); } return SliceBudget(TimeBudget(millis)); } void GCRuntime::gc(JSGCInvocationKind gckind, JS::gcreason::Reason reason) { invocationKind = gckind; collect(true, SliceBudget::unlimited(), reason); } void GCRuntime::startGC(JSGCInvocationKind gckind, JS::gcreason::Reason reason, int64_t millis) { MOZ_ASSERT(!isIncrementalGCInProgress()); if (!JS::IsIncrementalGCEnabled(rt->contextFromMainThread())) { gc(gckind, reason); return; } invocationKind = gckind; collect(false, defaultBudget(reason, millis), reason); } void GCRuntime::gcSlice(JS::gcreason::Reason reason, int64_t millis) { MOZ_ASSERT(isIncrementalGCInProgress()); collect(false, defaultBudget(reason, millis), reason); } void GCRuntime::finishGC(JS::gcreason::Reason reason) { MOZ_ASSERT(isIncrementalGCInProgress()); // If we're not collecting because we're out of memory then skip the // compacting phase if we need to finish an ongoing incremental GC // non-incrementally to avoid janking the browser. if (!IsOOMReason(initialReason)) { if (incrementalState == State::Compact) { abortGC(); return; } isCompacting = false; } collect(false, SliceBudget::unlimited(), reason); } void GCRuntime::abortGC() { checkCanCallAPI(); MOZ_ASSERT(!rt->mainThread.suppressGC); AutoEnqueuePendingParseTasksAfterGC aept(*this); gcstats::AutoGCSlice agc(stats, scanZonesBeforeGC(), invocationKind, SliceBudget::unlimited(), JS::gcreason::ABORT_GC); evictNursery(JS::gcreason::ABORT_GC); AutoTraceSession session(rt, JS::HeapState::MajorCollecting); number++; resetIncrementalGC(gc::AbortReason::AbortRequested, session.lock); } void GCRuntime::notifyDidPaint() { MOZ_ASSERT(CurrentThreadCanAccessRuntime(rt)); if (isIncrementalGCInProgress() && !interFrameGC && tunables.areRefreshFrameSlicesEnabled()) { JS::PrepareForIncrementalGC(rt->contextFromMainThread()); gcSlice(JS::gcreason::REFRESH_FRAME); } interFrameGC = false; } static bool ZonesSelected(JSRuntime* rt) { for (ZonesIter zone(rt, WithAtoms); !zone.done(); zone.next()) { if (zone->isGCScheduled()) return true; } return false; } void GCRuntime::startDebugGC(JSGCInvocationKind gckind, SliceBudget& budget) { MOZ_ASSERT(!isIncrementalGCInProgress()); if (!ZonesSelected(rt)) JS::PrepareForFullGC(rt->contextFromMainThread()); invocationKind = gckind; collect(false, budget, JS::gcreason::DEBUG_GC); } void GCRuntime::debugGCSlice(SliceBudget& budget) { MOZ_ASSERT(isIncrementalGCInProgress()); if (!ZonesSelected(rt)) JS::PrepareForIncrementalGC(rt->contextFromMainThread()); collect(false, budget, JS::gcreason::DEBUG_GC); } /* Schedule a full GC unless a zone will already be collected. */ void js::PrepareForDebugGC(JSRuntime* rt) { if (!ZonesSelected(rt)) JS::PrepareForFullGC(rt->contextFromMainThread()); } void GCRuntime::onOutOfMallocMemory() { // Stop allocating new chunks. allocTask.cancel(GCParallelTask::CancelAndWait); // Make sure we release anything queued for release. decommitTask.join(); // Wait for background free of nursery huge slots to finish. nursery.waitBackgroundFreeEnd(); AutoLockGC lock(rt); onOutOfMallocMemory(lock); } void GCRuntime::onOutOfMallocMemory(const AutoLockGC& lock) { // Release any relocated arenas we may be holding on to, without releasing // the GC lock. releaseHeldRelocatedArenasWithoutUnlocking(lock); // Throw away any excess chunks we have lying around. freeEmptyChunks(rt, lock); // Immediately decommit as many arenas as possible in the hopes that this // might let the OS scrape together enough pages to satisfy the failing // malloc request. decommitAllWithoutUnlocking(lock); } void GCRuntime::minorGC(JS::gcreason::Reason reason, gcstats::Phase phase) { MOZ_ASSERT(!rt->isHeapBusy()); if (rt->mainThread.suppressGC) return; gcstats::AutoPhase ap(stats, phase); minorGCTriggerReason = JS::gcreason::NO_REASON; TraceLoggerThread* logger = TraceLoggerForMainThread(rt); AutoTraceLog logMinorGC(logger, TraceLogger_MinorGC); nursery.collect(rt, reason); MOZ_ASSERT(nursery.isEmpty()); blocksToFreeAfterMinorGC.freeAll(); { AutoLockGC lock(rt); for (ZonesIter zone(rt, WithAtoms); !zone.done(); zone.next()) maybeAllocTriggerZoneGC(zone, lock); } } void GCRuntime::disableGenerationalGC() { if (isGenerationalGCEnabled()) { evictNursery(JS::gcreason::API); nursery.disable(); } ++rt->gc.generationalDisabled; } void GCRuntime::enableGenerationalGC() { MOZ_ASSERT(generationalDisabled > 0); --generationalDisabled; if (generationalDisabled == 0) nursery.enable(); } bool GCRuntime::gcIfRequested() { // This method returns whether a major GC was performed. if (minorGCRequested()) minorGC(minorGCTriggerReason); if (majorGCRequested()) { if (!isIncrementalGCInProgress()) startGC(GC_NORMAL, majorGCTriggerReason); else gcSlice(majorGCTriggerReason); return true; } return false; } void js::gc::FinishGC(JSContext* cx) { if (JS::IsIncrementalGCInProgress(cx)) { JS::PrepareForIncrementalGC(cx); JS::FinishIncrementalGC(cx, JS::gcreason::API); } cx->gc.nursery.waitBackgroundFreeEnd(); } AutoPrepareForTracing::AutoPrepareForTracing(JSContext* cx, ZoneSelector selector) { js::gc::FinishGC(cx); session_.emplace(cx); } JSCompartment* js::NewCompartment(JSContext* cx, Zone* zone, JSPrincipals* principals, const JS::CompartmentOptions& options) { JSRuntime* rt = cx->runtime(); JS_AbortIfWrongThread(cx); ScopedJSDeletePtr<Zone> zoneHolder; if (!zone) { zone = cx->new_<Zone>(rt); if (!zone) return nullptr; zoneHolder.reset(zone); const JSPrincipals* trusted = rt->trustedPrincipals(); bool isSystem = principals && principals == trusted; if (!zone->init(isSystem)) { ReportOutOfMemory(cx); return nullptr; } } ScopedJSDeletePtr<JSCompartment> compartment(cx->new_<JSCompartment>(zone, options)); if (!compartment || !compartment->init(cx)) return nullptr; // Set up the principals. JS_SetCompartmentPrincipals(compartment, principals); AutoLockGC lock(rt); if (!zone->compartments.append(compartment.get())) { ReportOutOfMemory(cx); return nullptr; } if (zoneHolder && !rt->gc.zones.append(zone)) { ReportOutOfMemory(cx); return nullptr; } zoneHolder.forget(); return compartment.forget(); } void gc::MergeCompartments(JSCompartment* source, JSCompartment* target) { // The source compartment must be specifically flagged as mergable. This // also implies that the compartment is not visible to the debugger. MOZ_ASSERT(source->creationOptions_.mergeable()); MOZ_ASSERT(source->creationOptions_.invisibleToDebugger()); MOZ_ASSERT(source->creationOptions().addonIdOrNull() == target->creationOptions().addonIdOrNull()); JSContext* cx = source->contextFromMainThread(); AutoPrepareForTracing prepare(cx, SkipAtoms); // Cleanup tables and other state in the source compartment that will be // meaningless after merging into the target compartment. source->clearTables(); source->zone()->clearTables(); source->unsetIsDebuggee(); // The delazification flag indicates the presence of LazyScripts in a // compartment for the Debugger API, so if the source compartment created // LazyScripts, the flag must be propagated to the target compartment. if (source->needsDelazificationForDebugger()) target->scheduleDelazificationForDebugger(); // Release any relocated arenas which we may be holding on to as they might // be in the source zone cx->gc.releaseHeldRelocatedArenas(); // Fixup compartment pointers in source to refer to target, and make sure // type information generations are in sync. for (auto script = source->zone()->cellIter<JSScript>(); !script.done(); script.next()) { MOZ_ASSERT(script->compartment() == source); script->compartment_ = target; script->setTypesGeneration(target->zone()->types.generation); } for (auto group = source->zone()->cellIter<ObjectGroup>(); !group.done(); group.next()) { group->setGeneration(target->zone()->types.generation); group->compartment_ = target; } // Fixup zone pointers in source's zone to refer to target's zone. for (auto thingKind : AllAllocKinds()) { for (ArenaIter aiter(source->zone(), thingKind); !aiter.done(); aiter.next()) { Arena* arena = aiter.get(); arena->zone = target->zone(); } } // The source should be the only compartment in its zone. for (CompartmentsInZoneIter c(source->zone()); !c.done(); c.next()) MOZ_ASSERT(c.get() == source); // Merge the allocator, stats and UIDs in source's zone into target's zone. target->zone()->arenas.adoptArenas(cx, &source->zone()->arenas); target->zone()->usage.adopt(source->zone()->usage); target->zone()->adoptUniqueIds(source->zone()); // Merge other info in source's zone into target's zone. target->zone()->types.typeLifoAlloc.transferFrom(&source->zone()->types.typeLifoAlloc); } void GCRuntime::setFullCompartmentChecks(bool enabled) { MOZ_ASSERT(!rt->isHeapMajorCollecting()); fullCompartmentChecks = enabled; } #ifdef DEBUG /* Should only be called manually under gdb */ void PreventGCDuringInteractiveDebug() { TlsPerThreadData.get()->suppressGC++; } #endif void js::ReleaseAllJITCode(FreeOp* fop) { js::CancelOffThreadIonCompile(fop->runtime()); for (ZonesIter zone(fop->runtime(), SkipAtoms); !zone.done(); zone.next()) { zone->setPreservingCode(false); zone->discardJitCode(fop); } } void js::PurgeJITCaches(Zone* zone) { /* Discard Ion caches. */ for (auto script = zone->cellIter<JSScript>(); !script.done(); script.next()) jit::PurgeCaches(script); } void ArenaLists::normalizeBackgroundFinalizeState(AllocKind thingKind) { ArenaLists::BackgroundFinalizeState* bfs = &backgroundFinalizeState[thingKind]; switch (*bfs) { case BFS_DONE: break; default: MOZ_ASSERT_UNREACHABLE("Background finalization in progress, but it should not be."); break; } } void ArenaLists::adoptArenas(JSRuntime* rt, ArenaLists* fromArenaLists) { // GC should be inactive, but still take the lock as a kind of read fence. AutoLockGC lock(rt); fromArenaLists->purge(); for (auto thingKind : AllAllocKinds()) { // When we enter a parallel section, we join the background // thread, and we do not run GC while in the parallel section, // so no finalizer should be active! normalizeBackgroundFinalizeState(thingKind); fromArenaLists->normalizeBackgroundFinalizeState(thingKind); ArenaList* fromList = &fromArenaLists->arenaLists[thingKind]; ArenaList* toList = &arenaLists[thingKind]; fromList->check(); toList->check(); Arena* next; for (Arena* fromArena = fromList->head(); fromArena; fromArena = next) { // Copy fromArena->next before releasing/reinserting. next = fromArena->next; MOZ_ASSERT(!fromArena->isEmpty()); toList->insertAtCursor(fromArena); } fromList->clear(); toList->check(); } } bool ArenaLists::containsArena(JSRuntime* rt, Arena* needle) { AutoLockGC lock(rt); ArenaList& list = arenaLists[needle->getAllocKind()]; for (Arena* arena = list.head(); arena; arena = arena->next) { if (arena == needle) return true; } return false; } AutoSuppressGC::AutoSuppressGC(ExclusiveContext* cx) : suppressGC_(cx->perThreadData->suppressGC) { suppressGC_++; } AutoSuppressGC::AutoSuppressGC(JSCompartment* comp) : suppressGC_(comp->runtimeFromMainThread()->mainThread.suppressGC) { suppressGC_++; } AutoSuppressGC::AutoSuppressGC(JSContext* cx) : suppressGC_(cx->mainThread().suppressGC) { suppressGC_++; } bool js::UninlinedIsInsideNursery(const gc::Cell* cell) { return IsInsideNursery(cell); } #ifdef DEBUG AutoDisableProxyCheck::AutoDisableProxyCheck(JSRuntime* rt) : gc(rt->gc) { gc.disableStrictProxyChecking(); } AutoDisableProxyCheck::~AutoDisableProxyCheck() { gc.enableStrictProxyChecking(); } JS_FRIEND_API(void) JS::AssertGCThingMustBeTenured(JSObject* obj) { MOZ_ASSERT(obj->isTenured() && (!IsNurseryAllocable(obj->asTenured().getAllocKind()) || obj->getClass()->hasFinalize())); } JS_FRIEND_API(void) JS::AssertGCThingIsNotAnObjectSubclass(Cell* cell) { MOZ_ASSERT(cell); MOZ_ASSERT(cell->getTraceKind() != JS::TraceKind::Object); } JS_FRIEND_API(void) js::gc::AssertGCThingHasType(js::gc::Cell* cell, JS::TraceKind kind) { if (!cell) MOZ_ASSERT(kind == JS::TraceKind::Null); else if (IsInsideNursery(cell)) MOZ_ASSERT(kind == JS::TraceKind::Object); else MOZ_ASSERT(MapAllocToTraceKind(cell->asTenured().getAllocKind()) == kind); } JS_PUBLIC_API(size_t) JS::GetGCNumber() { JSRuntime* rt = js::TlsPerThreadData.get()->runtimeFromMainThread(); if (!rt) return 0; return rt->gc.gcNumber(); } #endif JS::AutoAssertNoGC::AutoAssertNoGC() : gc(nullptr), gcNumber(0) { js::PerThreadData* data = js::TlsPerThreadData.get(); if (data) { /* * GC's from off-thread will always assert, so off-thread is implicitly * AutoAssertNoGC. We still need to allow AutoAssertNoGC to be used in * code that works from both threads, however. We also use this to * annotate the off thread run loops. */ JSRuntime* runtime = data->runtimeIfOnOwnerThread(); if (runtime) { gc = &runtime->gc; gcNumber = gc->gcNumber(); gc->enterUnsafeRegion(); } } } JS::AutoAssertNoGC::AutoAssertNoGC(JSRuntime* rt) : gc(&rt->gc), gcNumber(rt->gc.gcNumber()) { gc->enterUnsafeRegion(); } JS::AutoAssertNoGC::AutoAssertNoGC(JSContext* cx) : gc(&cx->gc), gcNumber(cx->gc.gcNumber()) { gc->enterUnsafeRegion(); } JS::AutoAssertNoGC::~AutoAssertNoGC() { if (gc) { gc->leaveUnsafeRegion(); /* * The following backstop assertion should never fire: if we bumped the * gcNumber, we should have asserted because inUnsafeRegion was true. */ MOZ_ASSERT(gcNumber == gc->gcNumber(), "GC ran inside an AutoAssertNoGC scope."); } } JS::AutoAssertOnBarrier::AutoAssertOnBarrier(JSContext* cx) : context(cx), prev(cx->runtime()->allowGCBarriers()) { context->runtime()->allowGCBarriers_ = false; } JS::AutoAssertOnBarrier::~AutoAssertOnBarrier() { MOZ_ASSERT(!context->runtime()->allowGCBarriers_); context->runtime()->allowGCBarriers_ = prev; } #ifdef DEBUG JS::AutoAssertNoAlloc::AutoAssertNoAlloc(JSContext* cx) : gc(nullptr) { disallowAlloc(cx); } void JS::AutoAssertNoAlloc::disallowAlloc(JSRuntime* rt) { MOZ_ASSERT(!gc); gc = &rt->gc; gc->disallowAlloc(); } JS::AutoAssertNoAlloc::~AutoAssertNoAlloc() { if (gc) gc->allowAlloc(); } AutoAssertNoNurseryAlloc::AutoAssertNoNurseryAlloc(JSRuntime* rt) : gc(rt->gc) { gc.disallowNurseryAlloc(); } AutoAssertNoNurseryAlloc::~AutoAssertNoNurseryAlloc() { gc.allowNurseryAlloc(); } JS::AutoEnterCycleCollection::AutoEnterCycleCollection(JSContext* cx) : runtime(cx->runtime()) { MOZ_ASSERT(!runtime->isHeapBusy()); runtime->setHeapState(HeapState::CycleCollecting); } JS::AutoEnterCycleCollection::~AutoEnterCycleCollection() { MOZ_ASSERT(runtime->isCycleCollecting()); runtime->setHeapState(HeapState::Idle); } #endif JS::AutoAssertGCCallback::AutoAssertGCCallback(JSObject* obj) : AutoSuppressGCAnalysis() { MOZ_ASSERT(obj->runtimeFromMainThread()->isHeapCollecting()); } JS_FRIEND_API(const char*) JS::GCTraceKindToAscii(JS::TraceKind kind) { switch(kind) { #define MAP_NAME(name, _0, _1) case JS::TraceKind::name: return #name; JS_FOR_EACH_TRACEKIND(MAP_NAME); #undef MAP_NAME default: return "Invalid"; } } JS::GCCellPtr::GCCellPtr(const Value& v) : ptr(0) { if (v.isString()) ptr = checkedCast(v.toString(), JS::TraceKind::String); else if (v.isObject()) ptr = checkedCast(&v.toObject(), JS::TraceKind::Object); else if (v.isSymbol()) ptr = checkedCast(v.toSymbol(), JS::TraceKind::Symbol); else if (v.isPrivateGCThing()) ptr = checkedCast(v.toGCThing(), v.toGCThing()->getTraceKind()); else ptr = checkedCast(nullptr, JS::TraceKind::Null); } JS::TraceKind JS::GCCellPtr::outOfLineKind() const { MOZ_ASSERT((ptr & OutOfLineTraceKindMask) == OutOfLineTraceKindMask); MOZ_ASSERT(asCell()->isTenured()); return MapAllocToTraceKind(asCell()->asTenured().getAllocKind()); } bool JS::GCCellPtr::mayBeOwnedByOtherRuntime() const { return (is<JSString>() && as<JSString>().isPermanentAtom()) || (is<Symbol>() && as<Symbol>().isWellKnownSymbol()); } #ifdef JSGC_HASH_TABLE_CHECKS void js::gc::CheckHashTablesAfterMovingGC(JSRuntime* rt) { /* * Check that internal hash tables no longer have any pointers to things * that have been moved. */ rt->spsProfiler.checkStringsMapAfterMovingGC(); for (ZonesIter zone(rt, SkipAtoms); !zone.done(); zone.next()) { zone->checkUniqueIdTableAfterMovingGC(); zone->checkInitialShapesTableAfterMovingGC(); zone->checkBaseShapeTableAfterMovingGC(); JS::AutoCheckCannotGC nogc; for (auto baseShape = zone->cellIter<BaseShape>(); !baseShape.done(); baseShape.next()) { if (ShapeTable* table = baseShape->maybeTable(nogc)) table->checkAfterMovingGC(); } } for (CompartmentsIter c(rt, SkipAtoms); !c.done(); c.next()) { c->objectGroups.checkTablesAfterMovingGC(); c->dtoaCache.checkCacheAfterMovingGC(); c->checkWrapperMapAfterMovingGC(); c->checkScriptMapsAfterMovingGC(); if (c->debugEnvs) c->debugEnvs->checkHashTablesAfterMovingGC(rt); } } #endif JS_PUBLIC_API(void) JS::PrepareZoneForGC(Zone* zone) { zone->scheduleGC(); } JS_PUBLIC_API(void) JS::PrepareForFullGC(JSContext* cx) { for (ZonesIter zone(cx, WithAtoms); !zone.done(); zone.next()) zone->scheduleGC(); } JS_PUBLIC_API(void) JS::PrepareForIncrementalGC(JSContext* cx) { if (!JS::IsIncrementalGCInProgress(cx)) return; for (ZonesIter zone(cx, WithAtoms); !zone.done(); zone.next()) { if (zone->wasGCStarted()) PrepareZoneForGC(zone); } } JS_PUBLIC_API(bool) JS::IsGCScheduled(JSContext* cx) { for (ZonesIter zone(cx, WithAtoms); !zone.done(); zone.next()) { if (zone->isGCScheduled()) return true; } return false; } JS_PUBLIC_API(void) JS::SkipZoneForGC(Zone* zone) { zone->unscheduleGC(); } JS_PUBLIC_API(void) JS::GCForReason(JSContext* cx, JSGCInvocationKind gckind, gcreason::Reason reason) { MOZ_ASSERT(gckind == GC_NORMAL || gckind == GC_SHRINK); cx->gc.gc(gckind, reason); } JS_PUBLIC_API(void) JS::StartIncrementalGC(JSContext* cx, JSGCInvocationKind gckind, gcreason::Reason reason, int64_t millis) { MOZ_ASSERT(gckind == GC_NORMAL || gckind == GC_SHRINK); cx->gc.startGC(gckind, reason, millis); } JS_PUBLIC_API(void) JS::IncrementalGCSlice(JSContext* cx, gcreason::Reason reason, int64_t millis) { cx->gc.gcSlice(reason, millis); } JS_PUBLIC_API(void) JS::FinishIncrementalGC(JSContext* cx, gcreason::Reason reason) { cx->gc.finishGC(reason); } JS_PUBLIC_API(void) JS::AbortIncrementalGC(JSContext* cx) { cx->gc.abortGC(); } char16_t* JS::GCDescription::formatSliceMessage(JSContext* cx) const { UniqueChars cstr = cx->gc.stats.formatCompactSliceMessage(); size_t nchars = strlen(cstr.get()); UniqueTwoByteChars out(js_pod_malloc<char16_t>(nchars + 1)); if (!out) return nullptr; out.get()[nchars] = 0; CopyAndInflateChars(out.get(), cstr.get(), nchars); return out.release(); } char16_t* JS::GCDescription::formatSummaryMessage(JSContext* cx) const { UniqueChars cstr = cx->gc.stats.formatCompactSummaryMessage(); size_t nchars = strlen(cstr.get()); UniqueTwoByteChars out(js_pod_malloc<char16_t>(nchars + 1)); if (!out) return nullptr; out.get()[nchars] = 0; CopyAndInflateChars(out.get(), cstr.get(), nchars); return out.release(); } JS::dbg::GarbageCollectionEvent::Ptr JS::GCDescription::toGCEvent(JSContext* cx) const { return JS::dbg::GarbageCollectionEvent::Create(cx, cx->gc.stats, cx->gc.majorGCCount()); } char16_t* JS::GCDescription::formatJSON(JSContext* cx, uint64_t timestamp) const { UniqueChars cstr = cx->gc.stats.formatJsonMessage(timestamp); size_t nchars = strlen(cstr.get()); UniqueTwoByteChars out(js_pod_malloc<char16_t>(nchars + 1)); if (!out) return nullptr; out.get()[nchars] = 0; CopyAndInflateChars(out.get(), cstr.get(), nchars); return out.release(); } JS_PUBLIC_API(JS::GCSliceCallback) JS::SetGCSliceCallback(JSContext* cx, GCSliceCallback callback) { return cx->gc.setSliceCallback(callback); } JS_PUBLIC_API(JS::DoCycleCollectionCallback) JS::SetDoCycleCollectionCallback(JSContext* cx, JS::DoCycleCollectionCallback callback) { return cx->gc.setDoCycleCollectionCallback(callback); } JS_PUBLIC_API(JS::GCNurseryCollectionCallback) JS::SetGCNurseryCollectionCallback(JSContext* cx, GCNurseryCollectionCallback callback) { return cx->gc.setNurseryCollectionCallback(callback); } JS_PUBLIC_API(void) JS::DisableIncrementalGC(JSContext* cx) { cx->gc.disallowIncrementalGC(); } JS_PUBLIC_API(bool) JS::IsIncrementalGCEnabled(JSContext* cx) { return cx->gc.isIncrementalGCEnabled(); } JS_PUBLIC_API(bool) JS::IsIncrementalGCInProgress(JSContext* cx) { return cx->gc.isIncrementalGCInProgress(); } JS_PUBLIC_API(bool) JS::IsIncrementalBarrierNeeded(JSContext* cx) { if (cx->isHeapBusy()) return false; auto state = cx->gc.state(); return state != gc::State::NotActive && state <= gc::State::Sweep; } struct IncrementalReferenceBarrierFunctor { template <typename T> void operator()(T* t) { T::writeBarrierPre(t); } }; JS_PUBLIC_API(void) JS::IncrementalReferenceBarrier(GCCellPtr thing) { if (!thing) return; DispatchTyped(IncrementalReferenceBarrierFunctor(), thing); } JS_PUBLIC_API(void) JS::IncrementalValueBarrier(const Value& v) { js::GCPtrValue::writeBarrierPre(v); } JS_PUBLIC_API(void) JS::IncrementalObjectBarrier(JSObject* obj) { if (!obj) return; MOZ_ASSERT(!obj->zone()->runtimeFromMainThread()->isHeapMajorCollecting()); JSObject::writeBarrierPre(obj); } JS_PUBLIC_API(bool) JS::WasIncrementalGC(JSContext* cx) { return cx->gc.isIncrementalGc(); } JS::AutoDisableGenerationalGC::AutoDisableGenerationalGC(JSRuntime* rt) : gc(&rt->gc) { gc->disableGenerationalGC(); } JS::AutoDisableGenerationalGC::~AutoDisableGenerationalGC() { gc->enableGenerationalGC(); } JS_PUBLIC_API(bool) JS::IsGenerationalGCEnabled(JSRuntime* rt) { return rt->gc.isGenerationalGCEnabled(); } uint64_t js::gc::NextCellUniqueId(JSRuntime* rt) { return rt->gc.nextCellUniqueId(); } namespace js { namespace gc { namespace MemInfo { static bool GCBytesGetter(JSContext* cx, unsigned argc, Value* vp) { CallArgs args = CallArgsFromVp(argc, vp); args.rval().setNumber(double(cx->runtime()->gc.usage.gcBytes())); return true; } static bool GCMaxBytesGetter(JSContext* cx, unsigned argc, Value* vp) { CallArgs args = CallArgsFromVp(argc, vp); args.rval().setNumber(double(cx->runtime()->gc.tunables.gcMaxBytes())); return true; } static bool MallocBytesGetter(JSContext* cx, unsigned argc, Value* vp) { CallArgs args = CallArgsFromVp(argc, vp); args.rval().setNumber(double(cx->runtime()->gc.getMallocBytes())); return true; } static bool MaxMallocGetter(JSContext* cx, unsigned argc, Value* vp) { CallArgs args = CallArgsFromVp(argc, vp); args.rval().setNumber(double(cx->runtime()->gc.maxMallocBytesAllocated())); return true; } static bool GCHighFreqGetter(JSContext* cx, unsigned argc, Value* vp) { CallArgs args = CallArgsFromVp(argc, vp); args.rval().setBoolean(cx->runtime()->gc.schedulingState.inHighFrequencyGCMode()); return true; } static bool GCNumberGetter(JSContext* cx, unsigned argc, Value* vp) { CallArgs args = CallArgsFromVp(argc, vp); args.rval().setNumber(double(cx->runtime()->gc.gcNumber())); return true; } static bool MajorGCCountGetter(JSContext* cx, unsigned argc, Value* vp) { CallArgs args = CallArgsFromVp(argc, vp); args.rval().setNumber(double(cx->runtime()->gc.majorGCCount())); return true; } static bool MinorGCCountGetter(JSContext* cx, unsigned argc, Value* vp) { CallArgs args = CallArgsFromVp(argc, vp); args.rval().setNumber(double(cx->runtime()->gc.minorGCCount())); return true; } static bool ZoneGCBytesGetter(JSContext* cx, unsigned argc, Value* vp) { CallArgs args = CallArgsFromVp(argc, vp); args.rval().setNumber(double(cx->zone()->usage.gcBytes())); return true; } static bool ZoneGCTriggerBytesGetter(JSContext* cx, unsigned argc, Value* vp) { CallArgs args = CallArgsFromVp(argc, vp); args.rval().setNumber(double(cx->zone()->threshold.gcTriggerBytes())); return true; } static bool ZoneGCAllocTriggerGetter(JSContext* cx, unsigned argc, Value* vp) { CallArgs args = CallArgsFromVp(argc, vp); args.rval().setNumber(double(cx->zone()->threshold.allocTrigger(cx->runtime()->gc.schedulingState.inHighFrequencyGCMode()))); return true; } static bool ZoneMallocBytesGetter(JSContext* cx, unsigned argc, Value* vp) { CallArgs args = CallArgsFromVp(argc, vp); args.rval().setNumber(double(cx->zone()->gcMallocBytes)); return true; } static bool ZoneMaxMallocGetter(JSContext* cx, unsigned argc, Value* vp) { CallArgs args = CallArgsFromVp(argc, vp); args.rval().setNumber(double(cx->zone()->gcMaxMallocBytes)); return true; } static bool ZoneGCDelayBytesGetter(JSContext* cx, unsigned argc, Value* vp) { CallArgs args = CallArgsFromVp(argc, vp); args.rval().setNumber(double(cx->zone()->gcDelayBytes)); return true; } static bool ZoneGCHeapGrowthFactorGetter(JSContext* cx, unsigned argc, Value* vp) { CallArgs args = CallArgsFromVp(argc, vp); args.rval().setNumber(cx->zone()->threshold.gcHeapGrowthFactor()); return true; } static bool ZoneGCNumberGetter(JSContext* cx, unsigned argc, Value* vp) { CallArgs args = CallArgsFromVp(argc, vp); args.rval().setNumber(double(cx->zone()->gcNumber())); return true; } #ifdef JS_MORE_DETERMINISTIC static bool DummyGetter(JSContext* cx, unsigned argc, Value* vp) { CallArgs args = CallArgsFromVp(argc, vp); args.rval().setUndefined(); return true; } #endif } /* namespace MemInfo */ JSObject* NewMemoryInfoObject(JSContext* cx) { RootedObject obj(cx, JS_NewObject(cx, nullptr)); if (!obj) return nullptr; using namespace MemInfo; struct NamedGetter { const char* name; JSNative getter; } getters[] = { { "gcBytes", GCBytesGetter }, { "gcMaxBytes", GCMaxBytesGetter }, { "mallocBytesRemaining", MallocBytesGetter }, { "maxMalloc", MaxMallocGetter }, { "gcIsHighFrequencyMode", GCHighFreqGetter }, { "gcNumber", GCNumberGetter }, { "majorGCCount", MajorGCCountGetter }, { "minorGCCount", MinorGCCountGetter } }; for (auto pair : getters) { #ifdef JS_MORE_DETERMINISTIC JSNative getter = DummyGetter; #else JSNative getter = pair.getter; #endif if (!JS_DefineProperty(cx, obj, pair.name, UndefinedHandleValue, JSPROP_ENUMERATE | JSPROP_SHARED, getter, nullptr)) { return nullptr; } } RootedObject zoneObj(cx, JS_NewObject(cx, nullptr)); if (!zoneObj) return nullptr; if (!JS_DefineProperty(cx, obj, "zone", zoneObj, JSPROP_ENUMERATE)) return nullptr; struct NamedZoneGetter { const char* name; JSNative getter; } zoneGetters[] = { { "gcBytes", ZoneGCBytesGetter }, { "gcTriggerBytes", ZoneGCTriggerBytesGetter }, { "gcAllocTrigger", ZoneGCAllocTriggerGetter }, { "mallocBytesRemaining", ZoneMallocBytesGetter }, { "maxMalloc", ZoneMaxMallocGetter }, { "delayBytes", ZoneGCDelayBytesGetter }, { "heapGrowthFactor", ZoneGCHeapGrowthFactorGetter }, { "gcNumber", ZoneGCNumberGetter } }; for (auto pair : zoneGetters) { #ifdef JS_MORE_DETERMINISTIC JSNative getter = DummyGetter; #else JSNative getter = pair.getter; #endif if (!JS_DefineProperty(cx, zoneObj, pair.name, UndefinedHandleValue, JSPROP_ENUMERATE | JSPROP_SHARED, getter, nullptr)) { return nullptr; } } return obj; } const char* StateName(State state) { switch(state) { #define MAKE_CASE(name) case State::name: return #name; GCSTATES(MAKE_CASE) #undef MAKE_CASE } MOZ_MAKE_COMPILER_ASSUME_IS_UNREACHABLE("invalide gc::State enum value"); } void AutoAssertHeapBusy::checkCondition(JSRuntime *rt) { this->rt = rt; MOZ_ASSERT(rt->isHeapBusy()); } void AutoAssertEmptyNursery::checkCondition(JSRuntime *rt) { if (!noAlloc) noAlloc.emplace(rt); this->rt = rt; MOZ_ASSERT(rt->gc.nursery.isEmpty()); } AutoEmptyNursery::AutoEmptyNursery(JSRuntime *rt) : AutoAssertEmptyNursery() { MOZ_ASSERT(!rt->mainThread.suppressGC); rt->gc.stats.suspendPhases(); rt->gc.evictNursery(); rt->gc.stats.resumePhases(); checkCondition(rt); } } /* namespace gc */ } /* namespace js */ #ifdef DEBUG void js::gc::Cell::dump(FILE* fp) const { switch (getTraceKind()) { case JS::TraceKind::Object: reinterpret_cast<const JSObject*>(this)->dump(fp); break; case JS::TraceKind::String: js::DumpString(reinterpret_cast<JSString*>(const_cast<Cell*>(this)), fp); break; case JS::TraceKind::Shape: reinterpret_cast<const Shape*>(this)->dump(fp); break; default: fprintf(fp, "%s(%p)\n", JS::GCTraceKindToAscii(getTraceKind()), (void*) this); } } // For use in a debugger. void js::gc::Cell::dump() const { dump(stderr); } #endif JS_PUBLIC_API(bool) js::gc::detail::CellIsMarkedGrayIfKnown(const Cell* cell) { MOZ_ASSERT(cell); if (!cell->isTenured()) return false; // We ignore the gray marking state of cells and return false in two cases: // // 1) When OOM has caused us to clear the gcGrayBitsValid_ flag. // // 2) When we are in an incremental GC and examine a cell that is in a zone // that is not being collected. Gray targets of CCWs that are marked black // by a barrier will eventually be marked black in the next GC slice. auto tc = &cell->asTenured(); auto rt = tc->runtimeFromMainThread(); if (!rt->areGCGrayBitsValid() || (rt->gc.isIncrementalGCInProgress() && !tc->zone()->wasGCStarted())) { return false; } return detail::CellIsMarkedGray(tc); }