209 lines
9.0 KiB
C
209 lines
9.0 KiB
C
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// Copyright 2015 The Chromium Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style license that can be
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// found in the LICENSE file.
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#ifndef BASE_PROFILER_STACK_SAMPLING_PROFILER_H_
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#define BASE_PROFILER_STACK_SAMPLING_PROFILER_H_
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#include <memory>
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#include <vector>
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#include "base/base_export.h"
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#include "base/macros.h"
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#include "base/optional.h"
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#include "base/profiler/profile_builder.h"
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#include "base/profiler/sampling_profiler_thread_token.h"
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#include "base/synchronization/waitable_event.h"
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#include "base/threading/platform_thread.h"
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#include "base/time/time.h"
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namespace base {
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class Unwinder;
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class StackSampler;
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class StackSamplerTestDelegate;
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// StackSamplingProfiler periodically stops a thread to sample its stack, for
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// the purpose of collecting information about which code paths are
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// executing. This information is used in aggregate by UMA to identify hot
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// and/or janky code paths.
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//
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// Sample StackSamplingProfiler usage:
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//
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// // Create and customize params as desired.
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// base::StackStackSamplingProfiler::SamplingParams params;
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//
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// // To process the profiles, use a custom ProfileBuilder subclass:
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// class SubProfileBuilder : public base::ProfileBuilder {...}
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//
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// // Then create the profiler:
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// base::StackSamplingProfiler profiler(base::PlatformThread::CurrentId(),
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// params, std::make_unique<SubProfileBuilder>(...));
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//
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// // On Android the |sampler| is not implemented in base. So, client can pass
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// // in |sampler| to use while profiling.
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// base::StackSamplingProfiler profiler(base::PlatformThread::CurrentId(),
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// params, std::make_unique<SubProfileBuilder>(...), <optional> sampler);
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//
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// // Then start the profiling.
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// profiler.Start();
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// // ... work being done on the target thread here ...
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// // Optionally stop collection before complete per params.
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// profiler.Stop();
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//
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// The default SamplingParams causes stacks to be recorded in a single profile
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// at a 10Hz interval for a total of 30 seconds. All of these parameters may be
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// altered as desired.
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//
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// When a call stack profile is complete, or the profiler is stopped,
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// ProfileBuilder's OnProfileCompleted function is called from a thread created
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// by the profiler.
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class BASE_EXPORT StackSamplingProfiler {
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public:
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// Represents parameters that configure the sampling.
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struct BASE_EXPORT SamplingParams {
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// Time to delay before first samples are taken.
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TimeDelta initial_delay = TimeDelta::FromMilliseconds(0);
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// Number of samples to record per profile.
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int samples_per_profile = 300;
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// Interval between samples during a sampling profile. This is the desired
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// duration from the start of one sample to the start of the next sample.
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TimeDelta sampling_interval = TimeDelta::FromMilliseconds(100);
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// When true, keeps the average sampling interval = |sampling_interval|,
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// irrespective of how long each sample takes. If a sample takes too long,
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// keeping the interval constant will lock out the sampled thread. When
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// false, sample is created with an interval of |sampling_interval|,
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// excluding the time taken by a sample. The metrics collected will not be
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// accurate, since sampling could take arbitrary amount of time, but makes
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// sure that the sampled thread gets at least the interval amount of time to
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// run between samples.
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bool keep_consistent_sampling_interval = true;
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};
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// Creates a profiler for the specified thread. An optional |test_delegate|
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// can be supplied by tests.
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//
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// The caller must ensure that this object gets destroyed before the thread
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// exits.
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StackSamplingProfiler(SamplingProfilerThreadToken thread_token,
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const SamplingParams& params,
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std::unique_ptr<ProfileBuilder> profile_builder,
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StackSamplerTestDelegate* test_delegate = nullptr);
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// Same as above function, with custom |sampler| implementation. The sampler
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// on Android is not implemented in base.
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StackSamplingProfiler(const SamplingParams& params,
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std::unique_ptr<ProfileBuilder> profile_builder,
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std::unique_ptr<StackSampler> sampler);
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// Stops any profiling currently taking place before destroying the profiler.
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// This will block until profile_builder_'s OnProfileCompleted function has
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// executed if profiling has started but not already finished.
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~StackSamplingProfiler();
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// Initializes the profiler and starts sampling. Might block on a
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// WaitableEvent if this StackSamplingProfiler was previously started and
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// recently stopped, while the previous profiling phase winds down.
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void Start();
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// Stops the profiler and any ongoing sampling. This method will return
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// immediately with the profile_builder_'s OnProfileCompleted function being
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// run asynchronously. At most one more stack sample will be taken after this
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// method returns. Calling this function is optional; if not invoked profiling
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// terminates when all the profiling samples specified in the SamplingParams
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// are completed or the profiler object is destroyed, whichever occurs first.
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void Stop();
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// Adds an auxiliary unwinder to handle additional, non-native-code unwind
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// scenarios.
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void AddAuxUnwinder(std::unique_ptr<Unwinder> unwinder);
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// Test peer class. These functions are purely for internal testing of
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// StackSamplingProfiler; DO NOT USE within tests outside of this directory.
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// The functions are static because they interact with the sampling thread, a
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// singleton used by all StackSamplingProfiler objects. The functions can
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// only be called by the same thread that started the sampling.
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class BASE_EXPORT TestPeer {
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public:
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// Resets the internal state to that of a fresh start. This is necessary
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// so that tests don't inherit state from previous tests.
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static void Reset();
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// Returns whether the sampling thread is currently running or not.
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static bool IsSamplingThreadRunning();
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// Disables inherent idle-shutdown behavior.
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static void DisableIdleShutdown();
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// Initiates an idle shutdown task, as though the idle timer had expired,
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// causing the thread to exit. There is no "idle" check so this must be
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// called only when all sampling tasks have completed. This blocks until
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// the task has been executed, though the actual stopping of the thread
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// still happens asynchronously. Watch IsSamplingThreadRunning() to know
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// when the thread has exited. If |simulate_intervening_start| is true then
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// this method will make it appear to the shutdown task that a new profiler
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// was started between when the idle-shutdown was initiated and when it
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// runs.
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static void PerformSamplingThreadIdleShutdown(
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bool simulate_intervening_start);
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};
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private:
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// SamplingThread is a separate thread used to suspend and sample stacks from
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// the target thread.
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class SamplingThread;
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// Friend the global function from sample_metadata.cc so that it can call into
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// the function below.
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friend void ApplyMetadataToPastSamplesImpl(TimeTicks period_start,
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TimeTicks period_end,
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int64_t name_hash,
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Optional<int64_t> key,
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int64_t value);
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// Apply metadata to already recorded samples. See the
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// ApplyMetadataToPastSamples() docs in sample_metadata.h.
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static void ApplyMetadataToPastSamples(TimeTicks period_start,
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TimeTicks period_end,
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int64_t name_hash,
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Optional<int64_t> key,
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int64_t value);
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// The thread whose stack will be sampled.
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SamplingProfilerThreadToken thread_token_;
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const SamplingParams params_;
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// Receives the sampling data and builds a profile. The ownership of this
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// object will be transferred to the sampling thread when thread sampling
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// starts.
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std::unique_ptr<ProfileBuilder> profile_builder_;
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// Stack sampler which stops the thread and collects stack frames. The
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// ownership of this object will be transferred to the sampling thread when
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// thread sampling starts.
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std::unique_ptr<StackSampler> sampler_;
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// If an AuxUnwinder is added before Start() it will be saved here until it
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// can be passed to the sampling thread when thread sampling starts.
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std::unique_ptr<Unwinder> pending_aux_unwinder_;
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// This starts "signaled", is reset when sampling begins, and is signaled
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// when that sampling is complete and the profile_builder_'s
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// OnProfileCompleted function has executed.
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WaitableEvent profiling_inactive_;
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// An ID uniquely identifying this profiler to the sampling thread. This
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// will be an internal "null" value when no collection has been started.
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int profiler_id_;
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DISALLOW_COPY_AND_ASSIGN(StackSamplingProfiler);
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};
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} // namespace base
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#endif // BASE_PROFILER_STACK_SAMPLING_PROFILER_H_
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