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/* -*- Mode: C++; tab-width: 2; 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 */
// The Gecko Profiler is an always-on profiler that takes fast and low overhead
// samples of the program execution using only userspace functionality for
// portability. The goal of this module is to provide performance data in a
// generic cross-platform way without requiring custom tools or kernel support.
// Samples are collected to form a timeline with optional timeline event
// (markers) used for filtering. The samples include both native stacks and
// platform-independent "label stack" frames.
#ifndef BaseProfilerState_h
#define BaseProfilerState_h
// This header contains most functions that give information about the Base
// Profiler: Whether it is active or not, paused, the selected features, and
// some generic process and thread information.
// It is safe to include unconditionally, but uses of structs and functions must
// be guarded by `#ifdef MOZ_GECKO_PROFILER`.
#include "mozilla/BaseProfilerUtils.h"
# define AUTO_PROFILER_STATS(name)
namespace mozilla::baseprofiler {
[[nodiscard]] inline bool profiler_is_active() { return false; }
[[nodiscard]] inline bool profiler_is_active_and_unpaused() { return false; }
} // namespace mozilla::baseprofiler
# include "mozilla/Atomics.h"
# include "mozilla/Maybe.h"
# include <stdint.h>
# include <string>
// Uncomment the following line to display profiler runtime statistics at
// shutdown.
# include "mozilla/TimeStamp.h"
# endif
namespace mozilla::baseprofiler {
// This class gathers durations and displays some basic stats when destroyed.
// It is intended to be used as a static variable (see `AUTO_PROFILER_STATS`
// below), to display stats at the end of the program.
class StaticBaseProfilerStats {
explicit StaticBaseProfilerStats(const char* aName) : mName(aName) {}
~StaticBaseProfilerStats() {
// Using unsigned long long for computations and printfs.
using ULL = unsigned long long;
ULL n = static_cast<ULL>(mNumberDurations);
if (n != 0) {
ULL sumNs = static_cast<ULL>(mSumDurationsNs);
"[%d] Profiler stats `%s`: %llu ns / %llu = %llu ns, max %llu ns\n",
int(profiler_current_process_id().ToNumber()), mName, sumNs, n,
sumNs / n, static_cast<ULL>(mLongestDurationNs));
} else {
printf("[%d] Profiler stats `%s`: (nothing)\n",
int(profiler_current_process_id().ToNumber()), mName);
void AddDurationFrom(TimeStamp aStart) {
DurationNs duration = static_cast<DurationNs>(
(TimeStamp::Now() - aStart).ToMicroseconds() * 1000 + 0.5);
mSumDurationsNs += duration;
// Update mLongestDurationNs if this one is longer.
for (;;) {
DurationNs longest = mLongestDurationNs;
if (MOZ_LIKELY(longest >= duration)) {
// This duration is not the longest, nothing to do.
if (MOZ_LIKELY(mLongestDurationNs.compareExchange(longest, duration))) {
// Successfully updated `mLongestDurationNs` with the new value.
// Otherwise someone else just updated `mLongestDurationNs`, we need to
// try again by looping.
using DurationNs = uint64_t;
using Count = uint32_t;
Atomic<DurationNs> mSumDurationsNs{0};
Atomic<DurationNs> mLongestDurationNs{0};
Atomic<Count> mNumberDurations{0};
const char* mName;
// RAII object that measure its scoped lifetime duration and reports it to a
// `StaticBaseProfilerStats`.
class MOZ_RAII AutoProfilerStats {
explicit AutoProfilerStats(StaticBaseProfilerStats& aStats)
: mStats(aStats), mStart(TimeStamp::Now()) {}
~AutoProfilerStats() { mStats.AddDurationFrom(mStart); }
StaticBaseProfilerStats& mStats;
TimeStamp mStart;
// Macro that should be used to collect basic statistics from measurements of
// block durations, from where this macro is, until the end of its enclosing
// scope. The name is used in the static variable name and when displaying stats
// at the end of the program; Another location could use the same name but their
// stats will not be combined, so use different name if these locations should
// be distinguished.
# define AUTO_PROFILER_STATS(name) \
static ::mozilla::baseprofiler::StaticBaseProfilerStats sStat##name( \
#name); \
::mozilla::baseprofiler::AutoProfilerStats autoStat##name(sStat##name);
# define AUTO_PROFILER_STATS(name)
// Profiler features
// Higher-order macro containing all the feature info in one place. Define
// |MACRO| appropriately to extract the relevant parts. Note that the number
// values are used internally only and so can be changed without consequence.
// Any changes to this list should also be applied to the feature list in
// toolkit/components/extensions/schemas/geckoProfiler.json.
// *** Synchronize with lists in ProfilerState.h and geckoProfiler.json ***
MACRO(0, "java", Java, "Profile Java code, Android only") \
MACRO(1, "js", JS, \
"Get the JS engine to expose the JS stack to the profiler") \
/* The DevTools profiler doesn't want the native addresses. */ \
MACRO(2, "leaf", Leaf, "Include the C++ leaf node if not stackwalking") \
MACRO(3, "mainthreadio", MainThreadIO, "Add main thread file I/O") \
MACRO(4, "fileio", FileIO, \
"Add file I/O from all profiled threads, implies mainthreadio") \
MACRO(5, "fileioall", FileIOAll, \
"Add file I/O from all threads, implies fileio") \
MACRO(6, "noiostacks", NoIOStacks, \
"File I/O markers do not capture stacks, to reduce overhead") \
MACRO(7, "screenshots", Screenshots, \
"Take a snapshot of the window on every composition") \
MACRO(8, "seqstyle", SequentialStyle, \
"Disable parallel traversal in styling") \
MACRO(9, "stackwalk", StackWalk, \
"Walk the C++ stack, not available on all platforms") \
MACRO(10, "threads", Threads, "Profile the registered secondary threads") \
MACRO(11, "jstracer", JSTracer, "Enable tracing of the JavaScript engine") \
MACRO(12, "jsallocations", JSAllocations, \
"Have the JavaScript engine track allocations") \
MACRO(13, "nostacksampling", NoStackSampling, \
"Disable all stack sampling: Cancels \"js\", \"leaf\", " \
"\"stackwalk\" and labels") \
MACRO(14, "preferencereads", PreferenceReads, \
"Track when preferences are read") \
MACRO(15, "nativeallocations", NativeAllocations, \
"Collect the stacks from a smaller subset of all native " \
"allocations, biasing towards collecting larger allocations") \
MACRO(16, "ipcmessages", IPCMessages, \
"Have the IPC layer track cross-process messages") \
MACRO(17, "audiocallbacktracing", AudioCallbackTracing, \
"Audio callback tracing") \
MACRO(18, "cpu", CPUUtilization, "CPU utilization") \
MACRO(19, "notimerresolutionchange", NoTimerResolutionChange, \
"Do not adjust the timer resolution for fast sampling, so that " \
"other Firefox timers do not get affected") \
MACRO(20, "cpuallthreads", CPUAllThreads, \
"Sample the CPU utilization of all registered threads") \
MACRO(21, "samplingallthreads", SamplingAllThreads, \
"Sample the stacks of all registered threads") \
MACRO(22, "markersallthreads", MarkersAllThreads, \
"Record markers from all registered threads")
// *** Synchronize with lists in ProfilerState.h and geckoProfiler.json ***
struct ProfilerFeature {
# define DECLARE(n_, str_, Name_, desc_) \
static constexpr uint32_t Name_ = (1u << n_); \
[[nodiscard]] static constexpr bool Has##Name_(uint32_t aFeatures) { \
return aFeatures & Name_; \
} \
static constexpr void Set##Name_(uint32_t& aFeatures) { \
aFeatures |= Name_; \
} \
static constexpr void Clear##Name_(uint32_t& aFeatures) { \
aFeatures &= ~Name_; \
// Define a bitfield constant, a getter, and two setters for each feature.
# undef DECLARE
namespace detail {
// RacyFeatures is only defined in this header file so that its methods can
// be inlined into profiler_is_active(). Please do not use anything from the
// detail namespace outside the profiler.
// Within the profiler's code, the preferred way to check profiler activeness
// and features is via ActivePS(). However, that requires locking gPSMutex.
// There are some hot operations where absolute precision isn't required, so we
// duplicate the activeness/feature state in a lock-free manner in this class.
class RacyFeatures {
MFBT_API static void SetActive(uint32_t aFeatures);
MFBT_API static void SetInactive();
MFBT_API static void SetPaused();
MFBT_API static void SetUnpaused();
MFBT_API static void SetSamplingPaused();
MFBT_API static void SetSamplingUnpaused();
[[nodiscard]] MFBT_API static bool IsActive();
[[nodiscard]] MFBT_API static bool IsActiveWithFeature(uint32_t aFeature);
// True if profiler is active, and not fully paused.
// Note that periodic sampling *could* be paused!
[[nodiscard]] MFBT_API static bool IsActiveAndUnpaused();
// True if profiler is active, and sampling is not paused (though generic
// `SetPaused()` or specific `SetSamplingPaused()`).
[[nodiscard]] MFBT_API static bool IsActiveAndSamplingUnpaused();
static constexpr uint32_t Active = 1u << 31;
static constexpr uint32_t Paused = 1u << 30;
static constexpr uint32_t SamplingPaused = 1u << 29;
// Ensure Active/Paused don't overlap with any of the feature bits.
# define NO_OVERLAP(n_, str_, Name_, desc_) \
static_assert(ProfilerFeature::Name_ != SamplingPaused, \
"bad feature value");
# undef NO_OVERLAP
// We combine the active bit with the feature bits so they can be read or
// written in a single atomic operation.
// TODO: Could this be MFBT_DATA for better inlining optimization?
static Atomic<uint32_t, MemoryOrdering::Relaxed> sActiveAndFeatures;
MFBT_API bool IsThreadBeingProfiled();
} // namespace detail
// Get information from the profiler
// Is the profiler active? Note: the return value of this function can become
// immediately out-of-date. E.g. the profile might be active but then
// profiler_stop() is called immediately afterward. One common and reasonable
// pattern of usage is the following:
// if (profiler_is_active()) {
// ExpensiveData expensiveData = CreateExpensiveData();
// PROFILER_OPERATION(expensiveData);
// }
// where PROFILER_OPERATION is a no-op if the profiler is inactive. In this
// case the profiler_is_active() check is just an optimization -- it prevents
// us calling CreateExpensiveData() unnecessarily in most cases, but the
// expensive data will end up being created but not used if another thread
// stops the profiler between the CreateExpensiveData() and PROFILER_OPERATION
// calls.
[[nodiscard]] inline bool profiler_is_active() {
return baseprofiler::detail::RacyFeatures::IsActive();
// Same as profiler_is_active(), but also checks if the profiler is not paused.
[[nodiscard]] inline bool profiler_is_active_and_unpaused() {
return baseprofiler::detail::RacyFeatures::IsActiveAndUnpaused();
// Is the profiler active and unpaused, and is the current thread being
// profiled? (Same caveats and recommented usage as profiler_is_active().)
[[nodiscard]] inline bool profiler_thread_is_being_profiled() {
return baseprofiler::detail::RacyFeatures::IsActiveAndUnpaused() &&
// Is the profiler active and paused? Returns false if the profiler is inactive.
[[nodiscard]] MFBT_API bool profiler_is_paused();
// Is the profiler active and sampling is paused? Returns false if the profiler
// is inactive.
[[nodiscard]] MFBT_API bool profiler_is_sampling_paused();
// Is the current thread sleeping?
[[nodiscard]] MFBT_API bool profiler_thread_is_sleeping();
// Get all the features supported by the profiler that are accepted by
// profiler_start(). The result is the same whether the profiler is active or
// not.
[[nodiscard]] MFBT_API uint32_t profiler_get_available_features();
// Check if a profiler feature (specified via the ProfilerFeature type) is
// active. Returns false if the profiler is inactive. Note: the return value
// can become immediately out-of-date, much like the return value of
// profiler_is_active().
[[nodiscard]] MFBT_API bool profiler_feature_active(uint32_t aFeature);
// Returns true if any of the profiler mutexes are currently locked *on the
// current thread*. This may be used by re-entrant code that may call profiler
// functions while the same of a different profiler mutex is locked, which could
// deadlock.
[[nodiscard]] bool profiler_is_locked_on_current_thread();
} // namespace mozilla::baseprofiler
#endif // BaseProfilerState_h