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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 */
#ifndef gc_Statistics_h
#define gc_Statistics_h
#include "mozilla/Array.h"
#include "mozilla/Atomics.h"
#include "mozilla/EnumeratedArray.h"
#include "mozilla/IntegerRange.h"
#include "mozilla/Maybe.h"
#include "mozilla/TimeStamp.h"
#include "jspubtd.h"
#include "NamespaceImports.h"
#include "gc/GCEnum.h"
#include "js/AllocPolicy.h"
#include "js/SliceBudget.h"
#include "js/UniquePtr.h"
#include "js/Vector.h"
#include "vm/JSONPrinter.h"
namespace js {
namespace gcstats {
// Phase data is generated by a script. If you need to add phases, edit
// js/src/gc/
#include "gc/StatsPhasesGenerated.h"
// Counts can be incremented with Statistics::count(). They're reset at the end
// of a Major GC.
enum Count {
// Number of times a 'put' into a storebuffer overflowed, triggering a
// compaction
// Number of arenas relocated by compacting GC.
// Stats can be set with Statistics::setStat(). They're not reset automatically.
enum Stat {
// Number of strings tenured.
// Number of object types pretenured this minor GC.
// Number of realms that had nursery strings disabled due to large numbers
// being tenured.
// Number of BigInts tenured.
// Number of realms that had nursery BigInts disabled due to large numbers
// being tenured.
struct ZoneGCStats {
/* Number of zones collected in this GC. */
int collectedZoneCount = 0;
/* Number of zones that could have been collected in this GC. */
int collectableZoneCount = 0;
/* Total number of zones in the Runtime at the start of this GC. */
int zoneCount = 0;
/* Number of zones swept in this GC. */
int sweptZoneCount = 0;
/* Total number of compartments in all zones collected. */
int collectedCompartmentCount = 0;
/* Total number of compartments in the Runtime at the start of this GC. */
int compartmentCount = 0;
/* Total number of compartments swept by this GC. */
int sweptCompartmentCount = 0;
bool isFullCollection() const {
return collectedZoneCount == collectableZoneCount;
ZoneGCStats() = default;
struct Trigger {
size_t amount = 0;
size_t threshold = 0;
_(BeginCallback, "bgnCB", PhaseKind::GC_BEGIN) \
_(MinorForMajor, "evct4m", PhaseKind::EVICT_NURSERY_FOR_MAJOR_GC) \
_(WaitBgThread, "waitBG", PhaseKind::WAIT_BACKGROUND_THREAD) \
_(Prepare, "prep", PhaseKind::PREPARE) \
_(Mark, "mark", PhaseKind::MARK) \
_(Sweep, "sweep", PhaseKind::SWEEP) \
_(Compact, "cmpct", PhaseKind::COMPACT) \
_(EndCallback, "endCB", PhaseKind::GC_END) \
_(MinorGC, "minor", PhaseKind::MINOR_GC) \
_(EvictNursery, "evict", PhaseKind::EVICT_NURSERY) \
_(Barriers, "brrier", PhaseKind::BARRIER)
const char* ExplainAbortReason(GCAbortReason reason);
const char* ExplainInvocationKind(JSGCInvocationKind gckind);
* Struct for collecting timing statistics on a "phase tree". The tree is
* specified as a limited DAG, but the timings are collected for the whole tree
* that you would get by expanding out the DAG by duplicating subtrees rooted
* at nodes with multiple parents.
* During execution, a child phase can be activated multiple times, and the
* total time will be accumulated. (So for example, you can start and end
* PhaseKind::MARK_ROOTS multiple times before completing the parent phase.)
* Incremental GC is represented by recording separate timing results for each
* slice within the overall GC.
struct Statistics {
template <typename T, size_t Length>
using Array = mozilla::Array<T, Length>;
template <typename IndexType, IndexType SizeAsEnumValue, typename ValueType>
using EnumeratedArray =
mozilla::EnumeratedArray<IndexType, SizeAsEnumValue, ValueType>;
using TimeDuration = mozilla::TimeDuration;
using TimeStamp = mozilla::TimeStamp;
// Create a convenient type for referring to tables of phase times.
using PhaseTimeTable = EnumeratedArray<Phase, Phase::LIMIT, TimeDuration>;
static MOZ_MUST_USE bool initialize();
explicit Statistics(gc::GCRuntime* gc);
Statistics(const Statistics&) = delete;
Statistics& operator=(const Statistics&) = delete;
void beginPhase(PhaseKind phaseKind);
void endPhase(PhaseKind phaseKind);
void recordParallelPhase(PhaseKind phaseKind, TimeDuration duration);
// Occasionally, we may be in the middle of something that is tracked by
// this class, and we need to do something unusual (eg evict the nursery)
// that doesn't normally nest within the current phase. Suspend the
// currently tracked phase stack, at which time the caller is free to do
// other tracked operations.
// This also happens internally with the PhaseKind::MUTATOR "phase". While in
// this phase, any beginPhase will automatically suspend the non-GC phase,
// until that inner stack is complete, at which time it will automatically
// resume the non-GC phase. Explicit suspensions do not get auto-resumed.
void suspendPhases(PhaseKind suspension = PhaseKind::EXPLICIT_SUSPENSION);
// Resume a suspended stack of phases.
void resumePhases();
void beginSlice(const ZoneGCStats& zoneStats, JSGCInvocationKind gckind,
SliceBudget budget, JS::GCReason reason);
void endSlice();
MOZ_MUST_USE bool startTimingMutator();
MOZ_MUST_USE bool stopTimingMutator(double& mutator_ms, double& gc_ms);
// Note when we sweep a zone or compartment.
void sweptZone() { ++zoneStats.sweptZoneCount; }
void sweptCompartment() { ++zoneStats.sweptCompartmentCount; }
void reset(GCAbortReason reason) {
MOZ_ASSERT(reason != GCAbortReason::None);
if (!aborted) {
slices_.back().resetReason = reason;
void measureInitialHeapSize();
void adoptHeapSizeDuringIncrementalGC(Zone* mergedZone);
void nonincremental(GCAbortReason reason) {
MOZ_ASSERT(reason != GCAbortReason::None);
nonincrementalReason_ = reason;
writeLogMessage("Non-incremental reason: %s", nonincrementalReason());
bool nonincremental() const {
return nonincrementalReason_ != GCAbortReason::None;
const char* nonincrementalReason() const {
return ExplainAbortReason(nonincrementalReason_);
void count(Count s) { counts[s]++; }
uint32_t getCount(Count s) const { return uint32_t(counts[s]); }
void setStat(Stat s, uint32_t value) { stats[s] = value; }
uint32_t getStat(Stat s) const { return stats[s]; }
void recordTrigger(size_t amount, size_t threshold) {
recordedTrigger = mozilla::Some(Trigger{amount, threshold});
bool hasTrigger() const { return recordedTrigger.isSome(); }
void noteNurseryAlloc() { allocsSinceMinorGC.nursery++; }
// tenured allocs don't include nursery evictions.
void setAllocsSinceMinorGCTenured(uint32_t allocs) {
allocsSinceMinorGC.tenured = allocs;
uint32_t allocsSinceMinorGCNursery() { return allocsSinceMinorGC.nursery; }
uint32_t allocsSinceMinorGCTenured() { return allocsSinceMinorGC.tenured; }
uint32_t* addressOfAllocsSinceMinorGCNursery() {
return &allocsSinceMinorGC.nursery;
void beginNurseryCollection(JS::GCReason reason);
void endNurseryCollection(JS::GCReason reason);
TimeStamp beginSCC();
void endSCC(unsigned scc, TimeStamp start);
UniqueChars formatCompactSliceMessage() const;
UniqueChars formatCompactSummaryMessage() const;
UniqueChars formatDetailedMessage() const;
JS::GCSliceCallback setSliceCallback(JS::GCSliceCallback callback);
JS::GCNurseryCollectionCallback setNurseryCollectionCallback(
JS::GCNurseryCollectionCallback callback);
TimeDuration clearMaxGCPauseAccumulator();
TimeDuration getMaxGCPauseSinceClear();
PhaseKind currentPhaseKind() const;
struct SliceData {
SliceData(SliceBudget budget, mozilla::Maybe<Trigger> trigger,
JS::GCReason reason, TimeStamp start, size_t startFaults,
gc::State initialState);
SliceBudget budget;
JS::GCReason reason = JS::GCReason::NO_REASON;
mozilla::Maybe<Trigger> trigger;
gc::State initialState = gc::State::NotActive;
gc::State finalState = gc::State::NotActive;
GCAbortReason resetReason = GCAbortReason::None;
TimeStamp start;
TimeStamp end;
size_t startFaults = 0;
size_t endFaults = 0;
PhaseTimeTable phaseTimes;
PhaseTimeTable maxParallelTimes;
TimeDuration duration() const { return end - start; }
bool wasReset() const { return resetReason != GCAbortReason::None; }
typedef Vector<SliceData, 8, SystemAllocPolicy> SliceDataVector;
const SliceDataVector& slices() const { return slices_; }
TimeStamp start() const { return slices_[0].start; }
TimeStamp end() const { return slices_.back().end; }
TimeStamp creationTime() const { return creationTime_; }
// Occasionally print header lines for profiling information.
void maybePrintProfileHeaders();
// Print header line for profile times.
void printProfileHeader();
// Print total profile times on shutdown.
void printTotalProfileTimes();
// These JSON strings are used by the firefox profiler to display the GC
// markers.
// Return JSON for a whole major GC
UniqueChars renderJsonMessage() const;
// Return JSON for the timings of just the given slice.
UniqueChars renderJsonSlice(size_t sliceNum) const;
// Return JSON for the previous nursery collection.
UniqueChars renderNurseryJson() const;
#ifdef DEBUG
// Print a logging message.
void writeLogMessage(const char* fmt, ...);
void writeLogMessage(const char* fmt, ...){};
gc::GCRuntime* const gc;
/* File used for MOZ_GCTIMER output. */
FILE* gcTimerFile;
/* File used for JS_GC_DEBUG output. */
FILE* gcDebugFile;
ZoneGCStats zoneStats;
JSGCInvocationKind gckind;
GCAbortReason nonincrementalReason_;
SliceDataVector slices_;
/* Most recent time when the given phase started. */
EnumeratedArray<Phase, Phase::LIMIT, TimeStamp> phaseStartTimes;
#ifdef DEBUG
/* Most recent time when the given phase ended. */
EnumeratedArray<Phase, Phase::LIMIT, TimeStamp> phaseEndTimes;
TimeStamp creationTime_;
/* Bookkeeping for GC timings when timingMutator is true */
TimeStamp timedGCStart;
TimeDuration timedGCTime;
/* Total time in a given phase for this GC. */
PhaseTimeTable phaseTimes;
/* Number of events of this type for this GC. */
EnumeratedArray<Count, COUNT_LIMIT,
mozilla::Atomic<uint32_t, mozilla::ReleaseAcquire>>
/* Other GC statistics. */
EnumeratedArray<Stat, STAT_LIMIT, uint32_t> stats;
* These events cannot be kept in the above array, we need to take their
* address.
struct {
uint32_t nursery;
uint32_t tenured;
} allocsSinceMinorGC;
/* Total GC heap size before and after the GC ran. */
size_t preTotalHeapBytes;
size_t postTotalHeapBytes;
/* GC heap size for collected zones before GC ran. */
size_t preCollectedHeapBytes;
* If a GC slice was triggered by exceeding some threshold, record the
* threshold and the value that exceeded it. This happens before the slice
* starts so this is recorded here first and then transferred to SliceData.
mozilla::Maybe<Trigger> recordedTrigger;
/* GC numbers as of the beginning of the collection. */
uint64_t startingMinorGCNumber;
uint64_t startingMajorGCNumber;
uint64_t startingSliceNumber;
/* Records the maximum GC pause in an API-controlled interval. */
mutable TimeDuration maxPauseInInterval;
/* Phases that are currently on stack. */
Vector<Phase, MAX_PHASE_NESTING, SystemAllocPolicy> phaseStack;
* Certain phases can interrupt the phase stack, eg callback phases. When
* this happens, we move the suspended phases over to a sepearate list,
* terminated by a dummy PhaseKind::SUSPENSION phase (so that we can nest
* suspensions by suspending multiple stacks with a PhaseKind::SUSPENSION in
* between).
Vector<Phase, MAX_SUSPENDED_PHASES, SystemAllocPolicy> suspendedPhases;
/* Sweep times for SCCs of compartments. */
Vector<TimeDuration, 0, SystemAllocPolicy> sccTimes;
TimeDuration timeSinceLastGC;
JS::GCSliceCallback sliceCallback;
JS::GCNurseryCollectionCallback nurseryCollectionCallback;
* True if we saw an OOM while allocating slices or we saw an impossible
* timestamp. The statistics for this GC will be invalid.
bool aborted;
/* Profiling data. */
enum class ProfileKey {
#define DEFINE_TIME_KEY(name, text, phase) name,
using ProfileDurations =
EnumeratedArray<ProfileKey, ProfileKey::KeyCount, TimeDuration>;
TimeDuration profileThreshold_;
bool enableProfiling_;
ProfileDurations totalTimes_;
uint64_t sliceCount_;
JSContext* context();
Phase currentPhase() const;
Phase lookupChildPhase(PhaseKind phaseKind) const;
void beginGC(JSGCInvocationKind kind, const TimeStamp& currentTime);
void endGC();
void sendGCTelemetry();
void sendSliceTelemetry(const SliceData& slice);
void recordPhaseBegin(Phase phase);
void recordPhaseEnd(Phase phase);
void gcDuration(TimeDuration* total, TimeDuration* maxPause) const;
void sccDurations(TimeDuration* total, TimeDuration* maxPause) const;
void printStats();
void reportLongestPhaseInMajorGC(PhaseKind longest, int telemetryId);
UniqueChars formatCompactSlicePhaseTimes(
const PhaseTimeTable& phaseTimes) const;
UniqueChars formatDetailedDescription() const;
UniqueChars formatDetailedSliceDescription(unsigned i,
const SliceData& slice) const;
UniqueChars formatDetailedPhaseTimes(const PhaseTimeTable& phaseTimes) const;
UniqueChars formatDetailedTotals() const;
void formatJsonDescription(JSONPrinter&) const;
void formatJsonSliceDescription(unsigned i, const SliceData& slice,
JSONPrinter&) const;
void formatJsonPhaseTimes(const PhaseTimeTable& phaseTimes,
JSONPrinter&) const;
void formatJsonSlice(size_t sliceNum, JSONPrinter&) const;
double computeMMU(TimeDuration resolution) const;
void printSliceProfile();
static void printProfileTimes(const ProfileDurations& times);
struct MOZ_RAII AutoGCSlice {
AutoGCSlice(Statistics& stats, const ZoneGCStats& zoneStats,
JSGCInvocationKind gckind, SliceBudget budget,
JS::GCReason reason)
: stats(stats) {
stats.beginSlice(zoneStats, gckind, budget, reason);
~AutoGCSlice() { stats.endSlice(); }
Statistics& stats;
struct MOZ_RAII AutoPhase {
AutoPhase(Statistics& stats, PhaseKind phaseKind)
: stats(stats), phaseKind(phaseKind), enabled(true) {
AutoPhase(Statistics& stats, bool condition, PhaseKind phaseKind)
: stats(stats), phaseKind(phaseKind), enabled(condition) {
if (enabled) {
~AutoPhase() {
if (enabled) {
Statistics& stats;
PhaseKind phaseKind;
bool enabled;
struct MOZ_RAII AutoSCC {
AutoSCC(Statistics& stats, unsigned scc) : stats(stats), scc(scc) {
start = stats.beginSCC();
~AutoSCC() { stats.endSCC(scc, start); }
Statistics& stats;
unsigned scc;
mozilla::TimeStamp start;
} /* namespace gcstats */
} /* namespace js */
#endif /* gc_Statistics_h */