Temporary commit to evaluate perf impact of prototype CPU profiler

base/profiler/cpu_profiler.h

+// 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.
+
+#ifndef BASE_PROFILER_CPU_PROFILER_H_
+#define BASE_PROFILER_CPU_PROFILER_H_
+
+#include <map>
+
+#include "base/base_export.h"
+#include "base/memory/scoped_ptr.h"
+#include "base/strings/string16.h"
+#include "base/synchronization/waitable_event.h"
+#include "base/timer/timer.h"
+
+#if defined(OS_WIN)
+struct _CONTEXT;
+#endif
+
+namespace base {
+
+class SamplingThread : public PlatformThread::Delegate {
+ public:
+  SamplingThread();
+  ~SamplingThread() override;
+
+  // Implementation of PlatformThread::Delegate:
+  void ThreadMain() override;
+
+  void Stop();
+
+  void GetSamples();
+
+ private:
+  bool thread_running_;
+
+  base::WaitableEvent waitable_event_;
+
+  DISALLOW_COPY_AND_ASSIGN(SamplingThread);
+};
+
+#if defined(OS_WIN)
+struct StackTraceEntry {
+  DWORD64 rsp;
+  DWORD64 rip;
+  HMODULE module;
+};
+#endif
+

[cpu_(ooo_6.6-7.5), 2015/02/05 22:41:47]

please review the const-ness of each member function on this class, this is
specially important since it appears can be accessed by multiple threads.

[Mike Wittman, 2015/02/06 20:01:14]

Done.

+class BASE_EXPORT CpuProfiler {
+ public:
+  static void Initialize(const std::map<std::string, std::string>* params);
+  static CpuProfiler* GetInstance();
+  static bool IsPlatformSupported();
+  static void Stop();

[cpu_(ooo_6.6-7.5), 2015/02/05 22:41:48]

wondering about Stop(), shouldn't it be a member instead of a static?

[Mike Wittman, 2015/02/06 20:01:14]

Yes, we can do away with the static instance entirely.

+
+  std::string GetStringParam(const std::string& key);
+  int GetIntParam(const std::string& key);
+  int64 GetInt64Param(const std::string& key);
+

[cpu_(ooo_6.6-7.5), 2015/02/05 22:41:48]

does OnTimer() need to be public?

[Mike Wittman, 2015/02/06 20:01:15]

No. Made it private.

+  void OnTimer();
+
+ private:
+  CpuProfiler();
+  ~CpuProfiler();
+
+  void SetParams(const std::map<std::string, std::string>& params);
+
+  void GetThreadIds();
+
+#if defined(OS_WIN)
+  void ProcessStack(StackTraceEntry* stack, int stack_depth);
+
+  HANDLE main_thread_;
+  int main_thread_stack_depth_;
+  StackTraceEntry main_thread_stack_[64];
+
+  std::map<HMODULE, base::string16> modules_;
+#endif
+
+  static CpuProfiler* g_instance_;
+
+  std::map<std::string, std::string> params_;
+
+  scoped_ptr<SamplingThread> sampling_thread_;

[cpu_(ooo_6.6-7.5), 2015/02/05 22:41:47]

seems SamplingThread is an internal artifact. Is it not?

If so you should move it to the cc file and have here just a fwd declaration.

[Mike Wittman, 2015/02/06 20:01:14]

Yes, done.

+  PlatformThreadHandle sampling_thread_handle_;
+
+  DISALLOW_COPY_AND_ASSIGN(CpuProfiler);
+};
+
+}  // namespace base
+
+#endif   // BASE_PROFILER_CPU_PROFILER_H_