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/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* 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 */
#include "ProfileBufferEntry.h"
#include "BaseProfiler.h"
#include "mozilla/Maybe.h"
#include "mozilla/PowerOfTwo.h"
#include "mozilla/ProfileBufferChunkManagerSingle.h"
#include "mozilla/ProfileChunkedBuffer.h"
namespace mozilla {
namespace baseprofiler {
// Class storing most profiling data in a ProfileChunkedBuffer.
// This class is used as a queue of entries which, after construction, never
// allocates. This makes it safe to use in the profiler's "critical section".
class ProfileBuffer final {
// ProfileBuffer constructor
// @param aBuffer The in-session ProfileChunkedBuffer to use as buffer
// manager.
explicit ProfileBuffer(ProfileChunkedBuffer& aBuffer);
ProfileChunkedBuffer& UnderlyingChunkedBuffer() const { return mEntries; }
bool IsThreadSafe() const { return mEntries.IsThreadSafe(); }
// Add |aEntry| to the buffer, ignoring what kind of entry it is.
// Returns the position of the entry.
uint64_t AddEntry(const ProfileBufferEntry& aEntry);
// Add to the buffer a sample start (ThreadId) entry for aThreadId.
// Returns the position of the entry.
uint64_t AddThreadIdEntry(BaseProfilerThreadId aThreadId);
void CollectCodeLocation(const char* aLabel, const char* aStr,
uint32_t aFrameFlags, uint64_t aInnerWindowID,
const Maybe<uint32_t>& aLineNumber,
const Maybe<uint32_t>& aColumnNumber,
const Maybe<ProfilingCategoryPair>& aCategoryPair);
// Maximum size of a frameKey string that we'll handle.
static const size_t kMaxFrameKeyLength = 512;
// Stream JSON for samples in the buffer to aWriter, using the supplied
// UniqueStacks object.
// Only streams samples for the given thread ID and which were taken at or
// after aSinceTime. If ID is 0, ignore the stored thread ID; this should only
// be used when the buffer contains only one sample.
// Return the thread ID of the streamed sample(s), or 0.
BaseProfilerThreadId StreamSamplesToJSON(SpliceableJSONWriter& aWriter,
BaseProfilerThreadId aThreadId,
double aSinceTime,
UniqueStacks& aUniqueStacks) const;
void StreamMarkersToJSON(SpliceableJSONWriter& aWriter,
BaseProfilerThreadId aThreadId,
const TimeStamp& aProcessStartTime,
double aSinceTime,
UniqueStacks& aUniqueStacks) const;
void StreamPausedRangesToJSON(SpliceableJSONWriter& aWriter,
double aSinceTime) const;
void StreamProfilerOverheadToJSON(SpliceableJSONWriter& aWriter,
const TimeStamp& aProcessStartTime,
double aSinceTime) const;
void StreamCountersToJSON(SpliceableJSONWriter& aWriter,
const TimeStamp& aProcessStartTime,
double aSinceTime) const;
// Find (via |aLastSample|) the most recent sample for the thread denoted by
// |aThreadId| and clone it, patching in the current time as appropriate.
// Mutate |aLastSample| to point to the newly inserted sample.
// Returns whether duplication was successful.
bool DuplicateLastSample(BaseProfilerThreadId aThreadId,
const TimeStamp& aProcessStartTime,
Maybe<uint64_t>& aLastSample);
void DiscardSamplesBeforeTime(double aTime);
size_t SizeOfExcludingThis(MallocSizeOf aMallocSizeOf) const;
size_t SizeOfIncludingThis(MallocSizeOf aMallocSizeOf) const;
void CollectOverheadStats(TimeDuration aSamplingTime, TimeDuration aLocking,
TimeDuration aCleaning, TimeDuration aCounters,
TimeDuration aThreads);
ProfilerBufferInfo GetProfilerBufferInfo() const;
// Add |aEntry| to the provider ProfileChunkedBuffer.
// `static` because it may be used to add an entry to a `ProfileChunkedBuffer`
// that is not attached to a `ProfileBuffer`.
static ProfileBufferBlockIndex AddEntry(
ProfileChunkedBuffer& aProfileChunkedBuffer,
const ProfileBufferEntry& aEntry);
// Add a sample start (ThreadId) entry for aThreadId to the provided
// ProfileChunkedBuffer. Returns the position of the entry.
// `static` because it may be used to add an entry to a `ProfileChunkedBuffer`
// that is not attached to a `ProfileBuffer`.
static ProfileBufferBlockIndex AddThreadIdEntry(
ProfileChunkedBuffer& aProfileChunkedBuffer,
BaseProfilerThreadId aThreadId);
// The storage in which this ProfileBuffer stores its entries.
ProfileChunkedBuffer& mEntries;
// `BufferRangeStart()` and `BufferRangeEnd()` return `uint64_t` values
// corresponding to the first entry and past the last entry stored in
// `mEntries`.
// The returned values are not guaranteed to be stable, because other threads
// may also be accessing the buffer concurrently. But they will always
// increase, and can therefore give an indication of how far these values have
// *at least* reached. In particular:
// - Entries whose index is strictly less that `BufferRangeStart()` have been
// discarded by now, so any related data may also be safely discarded.
// - It is safe to try and read entries at any index strictly less than
// `BufferRangeEnd()` -- but note that these reads may fail by the time you
// request them, as old entries get overwritten by new ones.
uint64_t BufferRangeStart() const { return mEntries.GetState().mRangeStart; }
uint64_t BufferRangeEnd() const { return mEntries.GetState().mRangeEnd; }
// Single pre-allocated chunk (to avoid spurious mallocs), used when:
// - Duplicating sleeping stacks (hence scExpectedMaximumStackSize).
// - Adding JIT info.
// - Streaming stacks to JSON.
// Mutable because it's accessed from non-multithreaded const methods.
mutable ProfileBufferChunkManagerSingle mWorkerChunkManager{
ProfileBufferChunk::SizeofChunkMetadata() +
// Time from launch (us) when first sampling was recorded.
double mFirstSamplingTimeUs = 0.0;
// Time from launch (us) when last sampling was recorded.
double mLastSamplingTimeUs = 0.0;
// Sampling stats: Interval (us) between successive samplings.
ProfilerStats mIntervalsUs;
// Sampling stats: Total duration (us) of each sampling. (Split detail below.)
ProfilerStats mOverheadsUs;
// Sampling stats: Time (us) to acquire the lock before sampling.
ProfilerStats mLockingsUs;
// Sampling stats: Time (us) to discard expired data.
ProfilerStats mCleaningsUs;
// Sampling stats: Time (us) to collect counter data.
ProfilerStats mCountersUs;
// Sampling stats: Time (us) to sample thread stacks.
ProfilerStats mThreadsUs;
* Helper type used to implement ProfilerStackCollector. This type is used as
* the collector for MergeStacks by ProfileBuffer. It holds a reference to the
* buffer, as well as additional feature flags which are needed to control the
* data collection strategy
class ProfileBufferCollector final : public ProfilerStackCollector {
ProfileBufferCollector(ProfileBuffer& aBuf, uint64_t aSamplePos,
uint64_t aBufferRangeStart)
: mBuf(aBuf),
mBufferRangeStart(aBufferRangeStart) {
mSamplePositionInBuffer >= mBufferRangeStart,
"The sample position should always be after the buffer range start");
// Position at which the sample starts in the profiler buffer (which may be
// different from the buffer in which the sample data is collected here).
Maybe<uint64_t> SamplePositionInBuffer() override {
return Some(mSamplePositionInBuffer);
// Profiler buffer's range start (which may be different from the buffer in
// which the sample data is collected here).
Maybe<uint64_t> BufferRangeStart() override {
return Some(mBufferRangeStart);
virtual void CollectNativeLeafAddr(void* aAddr) override;
virtual void CollectProfilingStackFrame(
const ProfilingStackFrame& aFrame) override;
ProfileBuffer& mBuf;
uint64_t mSamplePositionInBuffer;
uint64_t mBufferRangeStart;
} // namespace baseprofiler
} // namespace mozilla