Metrics provider for statistical stack profiler

base/profiler/stack_sampling_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_STACK_SAMPLING_PROFILER_H_
+#define BASE_PROFILER_STACK_SAMPLING_PROFILER_H_
+
+#include <string>
+#include <vector>
+
+#include "base/base_export.h"
+#include "base/files/file_path.h"
+#include "base/memory/scoped_ptr.h"
+#include "base/strings/string16.h"
+#include "base/threading/platform_thread.h"
+#include "base/time/time.h"
+
+namespace base {
+
+// StackSamplingProfiler periodically stops a thread to sample its stack, for
+// the purpose of collecting information about which code paths are
+// executing. This information is used in aggregate by UMA to identify hot
+// and/or janky code paths. The current implementation samples periodically for
+// a short period after invoking Start.
+//
+// To use: create a StackSamplingProfiler, call Start to start the sampling,
+// then (optionally) call Stop to stop the sampling.
+class BASE_EXPORT StackSamplingProfiler {
+ public:
+  // Module represents the module (DLL or exe) corresponding to a stack frame.
+  struct Module {
+    // An opaque binary string that uniquely identifies a particular program
+    // version with high probability. This is parsed from headers of the loaded
+    // module.
+    // For binaries generated by GNU tools:
+    //   Contents of the .note.gnu.build-id field.
+    // On Windows:
+    //   GUID + AGE in the debug image headers of a module.
+    std::string id;
+    // The filename of the module.
+    base::FilePath filename;
+  };
+
+  // Frame represents an individual sampled stack frame with module information.
+  struct Frame {
+    // Instruction pointer subtracted by module base.
+    uint64 ip_offset;
+    // Index of the module in the array of modules. We don't represent module
+    // state directly here to save space.
+    int module_index;
+  };
+
+  // Sample represents a set of stack frames.
+  using Sample = std::vector<Frame>;
+
+  // Profile represents a set of samples.
+  struct Profile {
+    Profile();
+    ~Profile();
+
+    std::vector<Module> modules;
+    std::vector<Sample> samples;
+    // Duration of this profile.
+    base::TimeDelta profile_duration;
+    // Time between samples.
+    base::TimeDelta sampling_period;
+  };
+
+  // NativeStackSampler abstracts the native implementation required to record a
+  // stack sample for a given thread.
+  class NativeStackSampler {
+   public:
+    virtual ~NativeStackSampler();
+
+    // Create a stack sampler that records samples for |thread_handle|. Returns
+    // null if this platform does not support stack sampling.
+    static scoped_ptr<NativeStackSampler> Create(PlatformThreadId thread_id);
+
+    // Notify the sampler that we're starting to record a new profile. This
+    // function is called on the SamplingThread.
+    virtual void ProfileRecordingStarting(Profile* profile) = 0;
+
+    // Record a stack sample. This function is called on the SamplingThread.
+    virtual void RecordStackSample(Sample* sample) = 0;
+
+    // Notify the sampler that we've stopped recording the current profile. This
+    // function is called on the SamplingThread.
+    virtual void ProfileRecordingStopped() = 0;
+
+   protected:
+    NativeStackSampler();
+
+   private:
+    DISALLOW_COPY_AND_ASSIGN(NativeStackSampler);
+  };
+
+  StackSamplingProfiler(PlatformThreadId thread_id);
+  ~StackSamplingProfiler();
+
+  // Initializes the profiler and starts sampling.
+  void Start();
+  // Stops the profiler and any ongoing sampling.
+  void Stop();
+
+  // Gets the pending profiles into *|profiles|. This function is thread safe.
+  static void GetPendingProfiles(std::vector<Profile>* profiles);
+
+ private:
+  class SamplingThread;
+  struct SamplingThreadDeleter {
+    void operator() (SamplingThread* thread) const;
+  };
+
+  void CollectPendingProfiles(const std::vector<Profile>& profiles);
+
+  PlatformThreadId thread_id_;
+
+  scoped_ptr<SamplingThread, SamplingThreadDeleter> sampling_thread_;
+  scoped_ptr<NativeStackSampler> native_sampler_;
+
+  DISALLOW_COPY_AND_ASSIGN(StackSamplingProfiler);
+};
+
+// Defined to allow equality check of Samples.
+BASE_EXPORT bool operator==(const StackSamplingProfiler::Frame &a,
+                            const StackSamplingProfiler::Frame &b);
+
+}  // namespace base
+
+#endif   // BASE_PROFILER_STACK_SAMPLING_PROFILER_H_