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authorMatt A. Tobin <mattatobin@localhost.localdomain>2018-02-02 04:16:08 -0500
committerMatt A. Tobin <mattatobin@localhost.localdomain>2018-02-02 04:16:08 -0500
commit5f8de423f190bbb79a62f804151bc24824fa32d8 (patch)
tree10027f336435511475e392454359edea8e25895d /mozglue/misc/TimeStamp_posix.cpp
parent49ee0794b5d912db1f95dce6eb52d781dc210db5 (diff)
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Add m-esr52 at 52.6.0
Diffstat (limited to 'mozglue/misc/TimeStamp_posix.cpp')
-rw-r--r--mozglue/misc/TimeStamp_posix.cpp362
1 files changed, 362 insertions, 0 deletions
diff --git a/mozglue/misc/TimeStamp_posix.cpp b/mozglue/misc/TimeStamp_posix.cpp
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+++ b/mozglue/misc/TimeStamp_posix.cpp
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+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* 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/. */
+
+//
+// Implement TimeStamp::Now() with POSIX clocks.
+//
+// The "tick" unit for POSIX clocks is simply a nanosecond, as this is
+// the smallest unit of time representable by struct timespec. That
+// doesn't mean that a nanosecond is the resolution of TimeDurations
+// obtained with this API; see TimeDuration::Resolution;
+//
+
+#include <sys/syscall.h>
+#include <time.h>
+#include <unistd.h>
+#include <string.h>
+
+#if defined(__DragonFly__) || defined(__FreeBSD__) \
+ || defined(__NetBSD__) || defined(__OpenBSD__)
+#include <sys/param.h>
+#include <sys/sysctl.h>
+#endif
+
+#if defined(__DragonFly__) || defined(__FreeBSD__)
+#include <sys/user.h>
+#endif
+
+#if defined(__NetBSD__)
+#undef KERN_PROC
+#define KERN_PROC KERN_PROC2
+#define KINFO_PROC struct kinfo_proc2
+#else
+#define KINFO_PROC struct kinfo_proc
+#endif
+
+#if defined(__DragonFly__)
+#define KP_START_SEC kp_start.tv_sec
+#define KP_START_USEC kp_start.tv_usec
+#elif defined(__FreeBSD__)
+#define KP_START_SEC ki_start.tv_sec
+#define KP_START_USEC ki_start.tv_usec
+#else
+#define KP_START_SEC p_ustart_sec
+#define KP_START_USEC p_ustart_usec
+#endif
+
+#include "mozilla/Sprintf.h"
+#include "mozilla/TimeStamp.h"
+#include <pthread.h>
+
+// Estimate of the smallest duration of time we can measure.
+static uint64_t sResolution;
+static uint64_t sResolutionSigDigs;
+
+static const uint16_t kNsPerUs = 1000;
+static const uint64_t kNsPerMs = 1000000;
+static const uint64_t kNsPerSec = 1000000000;
+static const double kNsPerMsd = 1000000.0;
+static const double kNsPerSecd = 1000000000.0;
+
+static uint64_t
+TimespecToNs(const struct timespec& aTs)
+{
+ uint64_t baseNs = uint64_t(aTs.tv_sec) * kNsPerSec;
+ return baseNs + uint64_t(aTs.tv_nsec);
+}
+
+static uint64_t
+ClockTimeNs()
+{
+ struct timespec ts;
+ // this can't fail: we know &ts is valid, and TimeStamp::Startup()
+ // checks that CLOCK_MONOTONIC is supported (and aborts if not)
+ clock_gettime(CLOCK_MONOTONIC, &ts);
+
+ // tv_sec is defined to be relative to an arbitrary point in time,
+ // but it would be madness for that point in time to be earlier than
+ // the Epoch. So we can safely assume that even if time_t is 32
+ // bits, tv_sec won't overflow while the browser is open. Revisit
+ // this argument if we're still building with 32-bit time_t around
+ // the year 2037.
+ return TimespecToNs(ts);
+}
+
+static uint64_t
+ClockResolutionNs()
+{
+ // NB: why not rely on clock_getres()? Two reasons: (i) it might
+ // lie, and (ii) it might return an "ideal" resolution that while
+ // theoretically true, could never be measured in practice. Since
+ // clock_gettime() likely involves a system call on your platform,
+ // the "actual" timing resolution shouldn't be lower than syscall
+ // overhead.
+
+ uint64_t start = ClockTimeNs();
+ uint64_t end = ClockTimeNs();
+ uint64_t minres = (end - start);
+
+ // 10 total trials is arbitrary: what we're trying to avoid by
+ // looping is getting unlucky and being interrupted by a context
+ // switch or signal, or being bitten by paging/cache effects
+ for (int i = 0; i < 9; ++i) {
+ start = ClockTimeNs();
+ end = ClockTimeNs();
+
+ uint64_t candidate = (start - end);
+ if (candidate < minres) {
+ minres = candidate;
+ }
+ }
+
+ if (0 == minres) {
+ // measurable resolution is either incredibly low, ~1ns, or very
+ // high. fall back on clock_getres()
+ struct timespec ts;
+ if (0 == clock_getres(CLOCK_MONOTONIC, &ts)) {
+ minres = TimespecToNs(ts);
+ }
+ }
+
+ if (0 == minres) {
+ // clock_getres probably failed. fall back on NSPR's resolution
+ // assumption
+ minres = 1 * kNsPerMs;
+ }
+
+ return minres;
+}
+
+namespace mozilla {
+
+double
+BaseTimeDurationPlatformUtils::ToSeconds(int64_t aTicks)
+{
+ return double(aTicks) / kNsPerSecd;
+}
+
+double
+BaseTimeDurationPlatformUtils::ToSecondsSigDigits(int64_t aTicks)
+{
+ // don't report a value < mResolution ...
+ int64_t valueSigDigs = sResolution * (aTicks / sResolution);
+ // and chop off insignificant digits
+ valueSigDigs = sResolutionSigDigs * (valueSigDigs / sResolutionSigDigs);
+ return double(valueSigDigs) / kNsPerSecd;
+}
+
+int64_t
+BaseTimeDurationPlatformUtils::TicksFromMilliseconds(double aMilliseconds)
+{
+ double result = aMilliseconds * kNsPerMsd;
+ if (result > INT64_MAX) {
+ return INT64_MAX;
+ } else if (result < INT64_MIN) {
+ return INT64_MIN;
+ }
+
+ return result;
+}
+
+int64_t
+BaseTimeDurationPlatformUtils::ResolutionInTicks()
+{
+ return static_cast<int64_t>(sResolution);
+}
+
+static bool gInitialized = false;
+
+void
+TimeStamp::Startup()
+{
+ if (gInitialized) {
+ return;
+ }
+
+ struct timespec dummy;
+ if (clock_gettime(CLOCK_MONOTONIC, &dummy) != 0) {
+ MOZ_CRASH("CLOCK_MONOTONIC is absent!");
+ }
+
+ sResolution = ClockResolutionNs();
+
+ // find the number of significant digits in sResolution, for the
+ // sake of ToSecondsSigDigits()
+ for (sResolutionSigDigs = 1;
+ !(sResolutionSigDigs == sResolution ||
+ 10 * sResolutionSigDigs > sResolution);
+ sResolutionSigDigs *= 10);
+
+ gInitialized = true;
+
+ return;
+}
+
+void
+TimeStamp::Shutdown()
+{
+}
+
+TimeStamp
+TimeStamp::Now(bool aHighResolution)
+{
+ return TimeStamp(ClockTimeNs());
+}
+
+#if defined(XP_LINUX) || defined(ANDROID)
+
+// Calculates the amount of jiffies that have elapsed since boot and up to the
+// starttime value of a specific process as found in its /proc/*/stat file.
+// Returns 0 if an error occurred.
+
+static uint64_t
+JiffiesSinceBoot(const char* aFile)
+{
+ char stat[512];
+
+ FILE* f = fopen(aFile, "r");
+ if (!f) {
+ return 0;
+ }
+
+ int n = fread(&stat, 1, sizeof(stat) - 1, f);
+
+ fclose(f);
+
+ if (n <= 0) {
+ return 0;
+ }
+
+ stat[n] = 0;
+
+ long long unsigned startTime = 0; // instead of uint64_t to keep GCC quiet
+ char* s = strrchr(stat, ')');
+
+ if (!s) {
+ return 0;
+ }
+
+ int rv = sscanf(s + 2,
+ "%*c %*d %*d %*d %*d %*d %*u %*u %*u %*u "
+ "%*u %*u %*u %*d %*d %*d %*d %*d %*d %llu",
+ &startTime);
+
+ if (rv != 1 || !startTime) {
+ return 0;
+ }
+
+ return startTime;
+}
+
+// Computes the interval that has elapsed between the thread creation and the
+// process creation by comparing the starttime fields in the respective
+// /proc/*/stat files. The resulting value will be a good approximation of the
+// process uptime. This value will be stored at the address pointed by aTime;
+// if an error occurred 0 will be stored instead.
+
+static void*
+ComputeProcessUptimeThread(void* aTime)
+{
+ uint64_t* uptime = static_cast<uint64_t*>(aTime);
+ long hz = sysconf(_SC_CLK_TCK);
+
+ *uptime = 0;
+
+ if (!hz) {
+ return nullptr;
+ }
+
+ char threadStat[40];
+ SprintfLiteral(threadStat, "/proc/self/task/%d/stat", (pid_t)syscall(__NR_gettid));
+
+ uint64_t threadJiffies = JiffiesSinceBoot(threadStat);
+ uint64_t selfJiffies = JiffiesSinceBoot("/proc/self/stat");
+
+ if (!threadJiffies || !selfJiffies) {
+ return nullptr;
+ }
+
+ *uptime = ((threadJiffies - selfJiffies) * kNsPerSec) / hz;
+ return nullptr;
+}
+
+// Computes and returns the process uptime in us on Linux & its derivatives.
+// Returns 0 if an error was encountered.
+
+uint64_t
+TimeStamp::ComputeProcessUptime()
+{
+ uint64_t uptime = 0;
+ pthread_t uptime_pthread;
+
+ if (pthread_create(&uptime_pthread, nullptr, ComputeProcessUptimeThread, &uptime)) {
+ MOZ_CRASH("Failed to create process uptime thread.");
+ return 0;
+ }
+
+ pthread_join(uptime_pthread, NULL);
+
+ return uptime / kNsPerUs;
+}
+
+#elif defined(__DragonFly__) || defined(__FreeBSD__) \
+ || defined(__NetBSD__) || defined(__OpenBSD__)
+
+// Computes and returns the process uptime in us on various BSD flavors.
+// Returns 0 if an error was encountered.
+
+uint64_t
+TimeStamp::ComputeProcessUptime()
+{
+ struct timespec ts;
+ int rv = clock_gettime(CLOCK_REALTIME, &ts);
+
+ if (rv == -1) {
+ return 0;
+ }
+
+ int mib[] = {
+ CTL_KERN,
+ KERN_PROC,
+ KERN_PROC_PID,
+ getpid(),
+#if defined(__NetBSD__) || defined(__OpenBSD__)
+ sizeof(KINFO_PROC),
+ 1,
+#endif
+ };
+ u_int mibLen = sizeof(mib) / sizeof(mib[0]);
+
+ KINFO_PROC proc;
+ size_t bufferSize = sizeof(proc);
+ rv = sysctl(mib, mibLen, &proc, &bufferSize, nullptr, 0);
+
+ if (rv == -1) {
+ return 0;
+ }
+
+ uint64_t startTime = ((uint64_t)proc.KP_START_SEC * kNsPerSec) +
+ (proc.KP_START_USEC * kNsPerUs);
+ uint64_t now = ((uint64_t)ts.tv_sec * kNsPerSec) + ts.tv_nsec;
+
+ if (startTime > now) {
+ return 0;
+ }
+
+ return (now - startTime) / kNsPerUs;
+}
+
+#else
+
+uint64_t
+TimeStamp::ComputeProcessUptime()
+{
+ return 0;
+}
+
+#endif
+
+} // namespace mozilla