Merge pull request #1065 from win7-7/Improve-dead-compartment-collection

Improve dead compartment collection

11 files changed, 166 insertions, 90 deletions

diff --git a/js/ipc/JavaScriptShared.cpp b/js/ipc/JavaScriptShared.cpp
index 9786243f2..961a3f910 100644
--- a/js/ipc/JavaScriptShared.cpp
+++ b/js/ipc/JavaScriptShared.cpp
@@ -61,6 +61,15 @@ IdToObjectMap::find(ObjectId id)
     return p->value();
 }
 
+JSObject*
+IdToObjectMap::findPreserveColor(ObjectId id)
+{
+    Table::Ptr p = table_.lookup(id);
+    if (!p) 
+        return nullptr;
+    return p->value().unbarrieredGet();
+}
+
 bool
 IdToObjectMap::add(ObjectId id, JSObject* obj)
 {
diff --git a/js/ipc/JavaScriptShared.h b/js/ipc/JavaScriptShared.h
index 4de153826..5ecec7429 100644
--- a/js/ipc/JavaScriptShared.h
+++ b/js/ipc/JavaScriptShared.h
@@ -96,6 +96,7 @@ class IdToObjectMap
 
     bool add(ObjectId id, JSObject* obj);
     JSObject* find(ObjectId id);
+    JSObject* findPreserveColor(ObjectId id);
     void remove(ObjectId id);
 
     void clear();
diff --git a/js/ipc/WrapperAnswer.cpp b/js/ipc/WrapperAnswer.cpp
index fc342bbb6..563f8f90d 100644
--- a/js/ipc/WrapperAnswer.cpp
+++ b/js/ipc/WrapperAnswer.cpp
@@ -789,7 +789,7 @@ WrapperAnswer::RecvDOMInstanceOf(const ObjectId& objId, const int& prototypeID,
 bool
 WrapperAnswer::RecvDropObject(const ObjectId& objId)
 {
-    JSObject* obj = objects_.find(objId);
+    JSObject* obj = objects_.findPreserveColor(objId);
     if (obj) {
         objectIdMap(objId.hasXrayWaiver()).remove(obj);
         objects_.remove(objId);
diff --git a/js/src/builtin/TypedObject.cpp b/js/src/builtin/TypedObject.cpp
index ae74f01bf..0dfc1123a 100644
--- a/js/src/builtin/TypedObject.cpp
+++ b/js/src/builtin/TypedObject.cpp
@@ -652,7 +652,7 @@ ArrayMetaTypeDescr::create(JSContext* cx,
     if (!CreateTraceList(cx, obj))
         return nullptr;
 
-    if (!cx->zone()->typeDescrObjects.put(obj)) {
+    if (!cx->zone()->addTypeDescrObject(cx, obj)) {
         ReportOutOfMemory(cx);
         return nullptr;
     }
@@ -993,8 +993,8 @@ StructMetaTypeDescr::create(JSContext* cx,
     if (!CreateTraceList(cx, descr))
         return nullptr;
 
-    if (!cx->zone()->typeDescrObjects.put(descr) ||
-        !cx->zone()->typeDescrObjects.put(fieldTypeVec))
+    if (!cx->zone()->addTypeDescrObject(cx, descr) ||
+        !cx->zone()->addTypeDescrObject(cx, fieldTypeVec))
     {
         ReportOutOfMemory(cx);
         return nullptr;
@@ -1165,10 +1165,8 @@ DefineSimpleTypeDescr(JSContext* cx,
     if (!CreateTraceList(cx, descr))
         return false;
 
-    if (!cx->zone()->typeDescrObjects.put(descr)) {
-        ReportOutOfMemory(cx);
+    if (!cx->zone()->addTypeDescrObject(cx, descr))
         return false;
-    }
 
     return true;
 }
diff --git a/js/src/gc/GCRuntime.h b/js/src/gc/GCRuntime.h
index 5c2576efd..f102e9ef0 100644
--- a/js/src/gc/GCRuntime.h
+++ b/js/src/gc/GCRuntime.h
@@ -900,7 +900,8 @@ class GCRuntime
 
     void requestMajorGC(JS::gcreason::Reason reason);
     SliceBudget defaultBudget(JS::gcreason::Reason reason, int64_t millis);
-    void budgetIncrementalGC(SliceBudget& budget, AutoLockForExclusiveAccess& lock);
+    void budgetIncrementalGC(JS::gcreason::Reason reason, SliceBudget& budget,
+                             AutoLockForExclusiveAccess& lock);
     void resetIncrementalGC(AbortReason reason, AutoLockForExclusiveAccess& lock);
 
     // Assert if the system state is such that we should never
@@ -915,6 +916,7 @@ class GCRuntime
     void collect(bool nonincrementalByAPI, SliceBudget budget, JS::gcreason::Reason reason) JS_HAZ_GC_CALL;
     MOZ_MUST_USE bool gcCycle(bool nonincrementalByAPI, SliceBudget& budget,
                               JS::gcreason::Reason reason);
+    bool shouldRepeatForDeadZone(JS::gcreason::Reason reason);
     void incrementalCollectSlice(SliceBudget& budget, JS::gcreason::Reason reason,
                                  AutoLockForExclusiveAccess& lock);
 
diff --git a/js/src/gc/RootMarking.cpp b/js/src/gc/RootMarking.cpp
index 93264084b..f5969bc1f 100644
--- a/js/src/gc/RootMarking.cpp
+++ b/js/src/gc/RootMarking.cpp
@@ -478,6 +478,7 @@ js::gc::GCRuntime::bufferGrayRoots()
     for (GCZonesIter zone(rt); !zone.done(); zone.next())
         MOZ_ASSERT(zone->gcGrayRoots.empty());
 
+    gcstats::AutoPhase ap(stats, gcstats::PHASE_BUFFER_GRAY_ROOTS);
 
     BufferGrayRootsTracer grayBufferer(rt);
     if (JSTraceDataOp op = grayRootTracer.op)
@@ -540,4 +541,3 @@ GCRuntime::resetBufferedGrayRoots() const
     for (GCZonesIter zone(rt); !zone.done(); zone.next())
         zone->gcGrayRoots.clearAndFree();
 }
-
diff --git a/js/src/gc/Zone.cpp b/js/src/gc/Zone.cpp
index ed099341c..f0cdde012 100644
--- a/js/src/gc/Zone.cpp
+++ b/js/src/gc/Zone.cpp
@@ -370,6 +370,21 @@ Zone::fixupAfterMovingGC()
     fixupInitialShapeTable();
 }
 
+bool
+Zone::addTypeDescrObject(JSContext* cx, HandleObject obj)
+{
+    // Type descriptor objects are always tenured so we don't need post barriers
+    // on the set.
+    MOZ_ASSERT(!IsInsideNursery(obj));
+    
+    if (!typeDescrObjects.put(obj)) {
+        ReportOutOfMemory(cx);
+        return false;
+    }
+    
+    return true;
+}
+    
 ZoneList::ZoneList()
   : head(nullptr), tail(nullptr)
 {}
diff --git a/js/src/gc/Zone.h b/js/src/gc/Zone.h
index 50d06319d..c8520ed55 100644
--- a/js/src/gc/Zone.h
+++ b/js/src/gc/Zone.h
@@ -349,10 +349,17 @@ struct Zone : public JS::shadow::Zone,
     // Keep track of all TypeDescr and related objects in this compartment.
     // This is used by the GC to trace them all first when compacting, since the
     // TypedObject trace hook may access these objects.
-    using TypeDescrObjectSet = js::GCHashSet<js::HeapPtr<JSObject*>,
-                                             js::MovableCellHasher<js::HeapPtr<JSObject*>>,
+	
+     //
+     // There are no barriers here - the set contains only tenured objects so no
+     // post-barrier is required, and these are weak references so no pre-barrier
+     // is required.
+     using TypeDescrObjectSet = js::GCHashSet<JSObject*,
+                                             js::MovableCellHasher<JSObject*>,
                                              js::SystemAllocPolicy>;
     JS::WeakCache<TypeDescrObjectSet> typeDescrObjects;
+	
+    bool addTypeDescrObject(JSContext* cx, HandleObject obj);
 
 
     // Malloc counter to measure memory pressure for GC scheduling. It runs from
diff --git a/js/src/jsgc.cpp b/js/src/jsgc.cpp
index 8cee9ec09..194468c5d 100644
--- a/js/src/jsgc.cpp
+++ b/js/src/jsgc.cpp
@@ -1524,19 +1524,11 @@ GCMarker::delayMarkingChildren(const void* thing)
 }
 
 inline void
-ArenaLists::prepareForIncrementalGC(JSRuntime* rt)
+ArenaLists::prepareForIncrementalGC()
 {
+    purge();
     for (auto i : AllAllocKinds()) {
-        FreeSpan* span = freeLists[i];
-        if (span != &placeholder) {
-            if (!span->isEmpty()) {
-                Arena* arena = span->getArena();
-                arena->allocatedDuringIncremental = true;
-                rt->gc.marker.delayMarkingArena(arena);
-            } else {
-                freeLists[i] = &placeholder;
-            }
-        }
+        arenaLists[i].moveCursorToEnd(); 
     }
 }
 
@@ -2251,7 +2243,7 @@ GCRuntime::updateTypeDescrObjects(MovingTracer* trc, Zone* zone)
 {
     zone->typeDescrObjects.sweep();
     for (auto r = zone->typeDescrObjects.all(); !r.empty(); r.popFront())
-        UpdateCellPointers(trc, r.front().get());
+        UpdateCellPointers(trc, r.front());
 }
 
 void
@@ -3579,6 +3571,23 @@ RelazifyFunctions(Zone* zone, AllocKind kind)
     }
 }
 
+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)
 {
@@ -3602,7 +3611,7 @@ GCRuntime::beginMarkPhase(JS::gcreason::Reason reason, AutoLockForExclusiveAcces
 #endif
 
         /* Set up which zones will be collected. */
-        if (zone->isGCScheduled()) {
+        if (ShouldCollectZone(zone, reason)) {
             if (!zone->isAtomsZone()) {
                 any = true;
                 zone->setGCState(Zone::Mark);
@@ -3621,7 +3630,7 @@ GCRuntime::beginMarkPhase(JS::gcreason::Reason reason, AutoLockForExclusiveAcces
     for (CompartmentsIter c(rt, WithAtoms); !c.done(); c.next()) {
         c->marked = false;
         c->scheduledForDestruction = false;
-        c->maybeAlive = false;
+        c->maybeAlive = c->hasBeenEntered() || !c->zone()->isGCScheduled();
         if (shouldPreserveJITCode(c, currentTime, reason, canAllocateMoreCode))
             c->zone()->setPreservingCode(true);
     }
@@ -3641,6 +3650,7 @@ GCRuntime::beginMarkPhase(JS::gcreason::Reason reason, AutoLockForExclusiveAcces
      * 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()) {
@@ -3655,15 +3665,12 @@ GCRuntime::beginMarkPhase(JS::gcreason::Reason reason, AutoLockForExclusiveAcces
         return false;
 
     /*
-     * At the end of each incremental slice, we call prepareForIncrementalGC,
-     * which marks objects in all arenas that we're currently allocating
-     * into. This can cause leaks if unreachable objects are in these
-     * arenas. This purge call ensures that we only mark arenas that have had
-     * allocations after the incremental GC started.
+     * 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.purge();
+            zone->arenas.prepareForIncrementalGC();
     }
 
     MemProfiler::MarkTenuredStart(rt);
@@ -3748,12 +3755,10 @@ GCRuntime::beginMarkPhase(JS::gcreason::Reason reason, AutoLockForExclusiveAcces
     gcstats::AutoPhase ap2(stats, gcstats::PHASE_MARK_ROOTS);
 
     if (isIncremental) {
-        gcstats::AutoPhase ap3(stats, gcstats::PHASE_BUFFER_GRAY_ROOTS);
         bufferGrayRoots();
+        markCompartments();
     }
-
-    markCompartments();
-
+     
     return true;
 }
 
@@ -3766,9 +3771,14 @@ GCRuntime::markCompartments()
      * 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 incoming cross-compartment edges, or
-     *   (2) an object in the compartment was marked during root marking, either
-     *       as a black root or a gray root.
+     *   (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
@@ -3786,26 +3796,37 @@ GCRuntime::markCompartments()
      * allocation and read barriers during JS_TransplantObject and the like.
      */
 
-    /* Set the maybeAlive flag based on cross-compartment edges. */
-    for (CompartmentsIter c(rt, SkipAtoms); !c.done(); c.next()) {
-        for (JSCompartment::WrapperEnum e(c); !e.empty(); e.popFront()) {
+    /* 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)
+            if (dest && !dest->maybeAlive) {
                 dest->maybeAlive = true;
+                if (!workList.append(dest))
+                    return;
+            }
         }
     }
 
-    /*
-     * For black roots, code in gc/Marking.cpp will already have set maybeAlive
-     * during MarkRuntime.
-     */
-
-    /* Propogate maybeAlive to scheduleForDestruction. */
-    for (GCCompartmentsIter c(rt); !c.done(); c.next()) {
-        if (!c->maybeAlive && !rt->isAtomsCompartment(c))
-            c->scheduledForDestruction = true;
+	
+    /* 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;
     }
 }
 
@@ -5306,7 +5327,7 @@ AutoGCSlice::~AutoGCSlice()
     for (ZonesIter zone(runtime, WithAtoms); !zone.done(); zone.next()) {
         if (zone->isGCMarking()) {
             zone->setNeedsIncrementalBarrier(true, Zone::UpdateJit);
-            zone->arenas.prepareForIncrementalGC(runtime);
+            zone->arenas.purge();
         } else {
             zone->setNeedsIncrementalBarrier(false, Zone::UpdateJit);
         }
@@ -5487,7 +5508,7 @@ gc::AbortReason
 gc::IsIncrementalGCUnsafe(JSRuntime* rt)
 {
     MOZ_ASSERT(!rt->mainThread.suppressGC);
-
+	
     if (rt->keepAtoms())
         return gc::AbortReason::KeepAtomsSet;
 
@@ -5498,9 +5519,17 @@ gc::IsIncrementalGCUnsafe(JSRuntime* rt)
 }
 
 void
-GCRuntime::budgetIncrementalGC(SliceBudget& budget, AutoLockForExclusiveAccess& lock)
+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();
@@ -5508,12 +5537,7 @@ GCRuntime::budgetIncrementalGC(SliceBudget& budget, AutoLockForExclusiveAccess&
         return;
     }
 
-    if (mode != JSGC_MODE_INCREMENTAL) {
-        resetIncrementalGC(AbortReason::ModeChange, lock);
-        budget.makeUnlimited();
-        stats.nonincremental(AbortReason::ModeChange);
-        return;
-    }
+  
 
     if (isTooMuchMalloc()) {
         budget.makeUnlimited();
@@ -5672,7 +5696,7 @@ GCRuntime::gcCycle(bool nonincrementalByAPI, SliceBudget& budget, JS::gcreason::
         stats.nonincremental(gc::AbortReason::NonIncrementalRequested);
         budget.makeUnlimited();
     } else {
-        budgetIncrementalGC(budget, session.lock);
+        budgetIncrementalGC(reason, budget, session.lock);
     }
 
     /* The GC was reset, so we need a do-over. */
@@ -5764,6 +5788,22 @@ GCRuntime::checkIfGCAllowedInCurrentState(JS::gcreason::Reason reason)
     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)
 {
@@ -5782,27 +5822,23 @@ GCRuntime::collect(bool nonincrementalByAPI, SliceBudget budget, JS::gcreason::R
     do {
         poked = false;
         bool wasReset = gcCycle(nonincrementalByAPI, budget, reason);
-
-        /* Need to re-schedule all zones for GC. */
-        if (poked && cleanUpEverything)
+      
+        bool repeatForDeadZone = false;
+        if (poked && cleanUpEverything) {
+            /* Need to re-schedule all zones for GC. */
             JS::PrepareForFullGC(rt->contextFromMainThread());
 
-        /*
-         * 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.
-         */
-        bool repeatForDeadZone = false;
-        if (!nonincrementalByAPI && !isIncrementalGCInProgress()) {
-            for (CompartmentsIter c(rt, SkipAtoms); !c.done(); c.next()) {
-                if (c->scheduledForDestruction) {
-                    nonincrementalByAPI = true;
-                    repeatForDeadZone = true;
-                    reason = JS::gcreason::COMPARTMENT_REVIVED;
-                    c->zone()->scheduleGC();
-                }
-            }
+       
+        } 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
diff --git a/js/src/jsgc.h b/js/src/jsgc.h
index d3cf31fe7..952fd6bae 100644
--- a/js/src/jsgc.h
+++ b/js/src/jsgc.h
@@ -61,7 +61,8 @@ enum class State {
     D(ModeChange) \
     D(MallocBytesTrigger) \
     D(GCBytesTrigger) \
-    D(ZoneChange)
+    D(ZoneChange) \
+    D(CompartmentRevived)
 enum class AbortReason {
 #define MAKE_REASON(name) name,
     GC_ABORT_REASONS(MAKE_REASON)
@@ -453,6 +454,12 @@ class ArenaList {
         check();
         return !*cursorp_;
     }
+	
+    void moveCursorToEnd() {
+        while (!isCursorAtEnd()) {
+            cursorp_ = &(*cursorp_)->next;
+        }
+    }
 
     // This can return nullptr.
     Arena* arenaAfterCursor() const {
@@ -739,7 +746,7 @@ class ArenaLists
             freeLists[i] = &placeholder;
     }
 
-    inline void prepareForIncrementalGC(JSRuntime* rt);
+    inline void prepareForIncrementalGC();
 
     /* Check if this arena is in use. */
     bool arenaIsInUse(Arena* arena, AllocKind kind) const {
diff --git a/js/src/jswatchpoint.cpp b/js/src/jswatchpoint.cpp
index 3cf43e219..e37323555 100644
--- a/js/src/jswatchpoint.cpp
+++ b/js/src/jswatchpoint.cpp
@@ -185,17 +185,18 @@ WatchpointMap::markAll(JSTracer* trc)
 {
     for (Map::Enum e(map); !e.empty(); e.popFront()) {
         Map::Entry& entry = e.front();
-        WatchKey key = entry.key();
-        WatchKey prior = key;
-        MOZ_ASSERT(JSID_IS_STRING(prior.id) || JSID_IS_INT(prior.id) || JSID_IS_SYMBOL(prior.id));
-
-        TraceEdge(trc, const_cast<PreBarrieredObject*>(&key.object),
-                   "held Watchpoint object");
-        TraceEdge(trc, const_cast<PreBarrieredId*>(&key.id), "WatchKey::id");
+        JSObject* object = entry.key().object;
+        jsid id = entry.key().id;
+        JSObject* priorObject = object;
+        jsid priorId = id;
+        MOZ_ASSERT(JSID_IS_STRING(priorId) || JSID_IS_INT(priorId) || JSID_IS_SYMBOL(priorId));
+
+        TraceManuallyBarrieredEdge(trc, &object, "held Watchpoint object");             
+        TraceManuallyBarrieredEdge(trc, &id, "WatchKey::id");		
         TraceEdge(trc, &entry.value().closure, "Watchpoint::closure");
 
-        if (prior.object != key.object || prior.id != key.id)
-            e.rekeyFront(key);
+        if (priorObject != object || priorId != id)
+            e.rekeyFront(WatchKey(object, id));
     }
 }