Metrics provider for statistical stack profiler

base/profiler/stack_sampling_profiler.cc

+// Copyright 2015 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "base/profiler/stack_sampling_profiler.h"
+
+#include <algorithm>
+
+#include "base/bind.h"
+#include "base/callback.h"
+#include "base/memory/singleton.h"
+#include "base/synchronization/lock.h"
+#include "base/synchronization/waitable_event.h"
+#include "base/timer/elapsed_timer.h"
+
+template <typename T> struct DefaultSingletonTraits;
+
+namespace base {
+
+namespace {
+// Time to delay before first samples are taken.
+const int64 kInitialDelayInMicroseconds = 0;
+// Number of sampling bursts to perform.
+const int kNumberOfBursts = 1;
+// Interval between sampling bursts. This is the desired duration from the start
+// of one burst to the start of the next burst.
+const int64 kBurstIntervalInMicroseconds = 10000000; // 10 sec
+// Number of samples to record per burst.
+const int kNumberOfSamples = 300;
+// Interval between samples during a sampling burst. This is the desired
+// duration from the start of one burst to the start of the next burst.
+const int64 kSamplingIntervalInMicroseconds = 100000; // 100 ms
+
+// Thread-safe singleton class that stores collected profiles waiting to be
+// processed.
+class PendingProfiles {
+public:
+  PendingProfiles();
+  ~PendingProfiles();
+
+  static PendingProfiles* GetInstance();
+
+  // Appends |profiles|. This function is thread safe.
+  void PutProfiles(const std::vector<StackSamplingProfiler::Profile>& profiles);
+  // Gets the pending profiles into *|profiles|. This function is thread safe.
+  void GetProfiles(std::vector<StackSamplingProfiler::Profile>* profiles);
+
+private:
+  base::Lock profiles_lock_;
+  std::vector<StackSamplingProfiler::Profile> profiles_;
+
+  DISALLOW_COPY_AND_ASSIGN(PendingProfiles);
+};
+
+PendingProfiles::PendingProfiles() {}
+
+PendingProfiles::~PendingProfiles() {}
+
+// static
+PendingProfiles* PendingProfiles::GetInstance() {
+  return Singleton<PendingProfiles>::get();
+}
+
+void PendingProfiles::PutProfiles(
+    const std::vector<StackSamplingProfiler::Profile>& profiles) {
+  base::AutoLock scoped_lock(profiles_lock_);
+  profiles_.insert(profiles_.end(), profiles.begin(), profiles.end());
+}
+
+void PendingProfiles::GetProfiles(
+    std::vector<StackSamplingProfiler::Profile>* profiles) {
+  profiles->clear();
+
+  base::AutoLock scoped_lock(profiles_lock_);
+  profiles_.swap(*profiles);
+}
+}  // namespace
+
+StackSamplingProfiler::Profile::Profile() {}
+
+StackSamplingProfiler::Profile::~Profile() {}
+
+class StackSamplingProfiler::SamplingThread : public PlatformThread::Delegate {
+ public:
+  // Samples stacks using |native_sampler|. When complete, invokes
+  // |profiles_callback| with the collected profiles. |profiles_callback| must
+  // be thread-safe and may consume the contents of the vector.
+  SamplingThread(
+      scoped_ptr<NativeStackSampler> native_sampler,
+      base::Callback<void(const std::vector<Profile>&)> profiles_callback);
+  ~SamplingThread() override;
+
+  // Implementation of PlatformThread::Delegate:
+  void ThreadMain() override;
+
+  void Stop();
+
+ private:
+  // Collects a profile from a single burst. Returns true if the profile was
+  // collected, or false if collection was stopped before it completed.
+  bool CollectProfile(Profile* profile, TimeDelta* elapsed_time);
+  // Collects profiles from all bursts, or until the sampling is stopped. If
+  // stopped before complete, |profiles| will contains only full bursts.
+  void CollectProfiles(std::vector<Profile>* profiles);
+
+  scoped_ptr<NativeStackSampler> native_sampler_;
+
+  base::WaitableEvent stop_event_;
+
+  base::Callback<void(const std::vector<Profile>&)> profiles_callback_;
+
+  DISALLOW_COPY_AND_ASSIGN(SamplingThread);
+};
+
+StackSamplingProfiler::SamplingThread::SamplingThread(
+    scoped_ptr<NativeStackSampler> native_sampler,
+    base::Callback<void(const std::vector<Profile>&)> profiles_callback)
+    : native_sampler_(native_sampler.Pass()),
+      stop_event_(false, false),
+      profiles_callback_(profiles_callback) {
+}
+
+StackSamplingProfiler::SamplingThread::~SamplingThread() {}
+
+void StackSamplingProfiler::SamplingThread::ThreadMain() {
+  PlatformThread::SetName("Chrome_SamplingProfilerThread");
+
+  std::vector<Profile> profiles;
+  CollectProfiles(&profiles);
+  profiles_callback_.Run(profiles);
+}
+
+bool StackSamplingProfiler::SamplingThread::CollectProfile(
+    Profile* profile, TimeDelta* elapsed_time) {
+  base::ElapsedTimer profile_timer;
+  Profile current_profile;
+  native_sampler_->ProfileRecordingStarting(&current_profile);
+  const TimeDelta sampling_interval =
+      TimeDelta::FromMicroseconds(kSamplingIntervalInMicroseconds);
+  current_profile.sampling_period = sampling_interval;
+  bool stopped_early = false;
+  for (int j = 0; j < kNumberOfSamples; ++j) {
+    base::ElapsedTimer sample_timer;
+    current_profile.samples.push_back(Sample());
+    native_sampler_->RecordStackSample(&current_profile.samples.back());
+    base::TimeDelta elapsed_sample_time = sample_timer.Elapsed();
+    if (j != kNumberOfSamples - 1) {
+      if (stop_event_.TimedWait(
+              std::max(sampling_interval - elapsed_sample_time, TimeDelta()))) {
+        stopped_early = true;
+        break;
+      }
+    }
+  }
+
+  *elapsed_time = profile_timer.Elapsed();
+  current_profile.profile_duration = *elapsed_time;
+  native_sampler_->ProfileRecordingStopped();
+
+  if (!stopped_early)
+    *profile = current_profile;
+
+  return !stopped_early;
+}
+
+void StackSamplingProfiler::SamplingThread::CollectProfiles(
+    std::vector<Profile>* profiles) {
+  if (stop_event_.TimedWait(TimeDelta::FromMicroseconds(
+          kInitialDelayInMicroseconds)))
+    return;
+
+  const TimeDelta burst_interval =
+      TimeDelta::FromMicroseconds(kBurstIntervalInMicroseconds);
+  for (int i = 0; i < kNumberOfBursts; ++i) {
+    Profile profile;
+    base::TimeDelta elapsed_profile_time;
+    if (CollectProfile(&profile, &elapsed_profile_time))
+      profiles->push_back(profile);
+    else
+      return;
+
+    if (stop_event_.TimedWait(
+            std::max(burst_interval - elapsed_profile_time, TimeDelta())))
+      return;
+  }
+}
+
+void StackSamplingProfiler::SamplingThread::Stop() {
+  stop_event_.Signal();
+}
+
+void StackSamplingProfiler::SamplingThreadDeleter::operator()(
+    SamplingThread* thread) const {
+  delete thread;
+}
+
+StackSamplingProfiler::NativeStackSampler::NativeStackSampler() {}
+
+StackSamplingProfiler::NativeStackSampler::~NativeStackSampler() {}
+
+StackSamplingProfiler::StackSamplingProfiler(PlatformThreadId thread_id)
+    : thread_id_(thread_id) {}
+
+StackSamplingProfiler::~StackSamplingProfiler() {}
+
+void StackSamplingProfiler::Start() {
+  native_sampler_ = NativeStackSampler::Create(thread_id_);
+  if (!native_sampler_)
+    return;
+
+  sampling_thread_.reset(
+      new SamplingThread(
+          native_sampler_.Pass(),
+          base::Bind(&PendingProfiles::PutProfiles,
+                     base::Unretained(PendingProfiles::GetInstance()))));
+  if (!PlatformThread::CreateNonJoinable(0, sampling_thread_.get()))
+    LOG(ERROR) << "failed to create thread";
+}
+
+void StackSamplingProfiler::Stop() {
+  if (sampling_thread_)
+    sampling_thread_->Stop();
+}
+
+// static
+void StackSamplingProfiler::GetPendingProfiles(std::vector<Profile>* profiles) {
+  PendingProfiles::GetInstance()->GetProfiles(profiles);
+}
+
+bool operator==(const StackSamplingProfiler::Frame &a,
+                const StackSamplingProfiler::Frame &b) {
+  return a.ip_offset == b.ip_offset && a.module_index == b.module_index;
+}
+
+}  // namespace base