Add process lifetime annotations to stack samples.

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 <stddef.h>
 
 #include <memory>
 #include <string>
 #include <vector>
 
+#include "base/atomicops.h"
 #include "base/base_export.h"
 #include "base/callback.h"
 #include "base/files/file_path.h"
 #include "base/macros.h"
 #include "base/strings/string16.h"
 #include "base/synchronization/waitable_event.h"
 #include "base/threading/platform_thread.h"
 #include "base/time/time.h"
 
 namespace base {
@@ skipping 76 matching lines @@
     Frame();
 
     // The sampled instruction pointer within the function.
     uintptr_t instruction_pointer;
 
     // Index of the module in CallStackProfile::modules. We don't represent
     // module state directly here to save space.
     size_t module_index;
   };
 
-  // Sample represents a set of stack frames.
-  using Sample = std::vector<Frame>;
+  // Sample represents a set of stack frames with some extra information.
+  struct BASE_EXPORT Sample {
+    Sample();
+    Sample(const Sample& sample);
+    ~Sample();
+
+    // These constructors are used only during testing.
+    Sample(const Frame& frame);
+    Sample(const std::vector<Frame>& frames);
+
+    // The entire stack frame when the sample is taken.
+    std::vector<Frame> frames;
+
+    // A bit-field indicating which process phases have passed. This can be
+    // used to tell where in the process lifetime the samples are taken. See
+    // ProcessPhase, above.

[Alexei Svitkine (slow), 2016/11/07 23:22:07]

This comment is not correct anymore since there's no ProcessPhase above now,
right?

Same for the one below.

Please rephrase to mention what these are now. (Even if the answer that these
are defined elsewhere and pass through function x).

[bcwhite, 2016/11/08 01:02:36]

Done.

+    uint32_t process_phases = 0;
+
+    // A bit-field indicating activities which were active when the frame was
+    // captured. See ProcessActivity, above.

[Alexei Svitkine (slow), 2016/11/07 23:22:07]

I think there needs to be a more in depth comment somewhere discussing the
distinction between phases and activities because it's not obvious to me.

[bcwhite, 2016/11/08 01:02:36]

Done.

+    uint32_t current_activities = 0;
+  };
 
   // CallStackProfile represents a set of samples.
   struct BASE_EXPORT CallStackProfile {
     CallStackProfile();
     CallStackProfile(CallStackProfile&& other);
     ~CallStackProfile();
 
     CallStackProfile& operator=(CallStackProfile&& other);
 
     CallStackProfile CopyForTesting() const;
@@ skipping 72 matching lines @@
 
   // Initializes the profiler and starts sampling.
   void Start();
 
   // Stops the profiler and any ongoing sampling. Calling this function is
   // optional; if not invoked profiling terminates when all the profiling bursts
   // specified in the SamplingParams are completed or the profiler is destroyed,
   // whichever occurs first.
   void Stop();
 
+  // Set the current system state that is recorded with each captured stack
+  // frame. These are all thread-safe so can be called from anywhere. The
+  // parameter values should be from an enumeration of the appropriate type
+  // with values ranging from 0 to 31, inclusive, and set bits within Sample
+  // fields of |process_phases| and |current_activities|. The actual meanings
+  // of these bits are defined (globally) by the caller(s).
+  static void SetProcessPhase(int phase);
+  static void RecordActivityBegin(int activity);
+  static void RecordActivityEnd(int activity);
+  static void ResetPhaseAndActivityForTesting();
+
  private:
   // SamplingThread is a separate thread used to suspend and sample stacks from
   // the target thread.
   class SamplingThread : public PlatformThread::Delegate {
    public:
     // Samples stacks using |native_sampler|. When complete, invokes
     // |completed_callback| with the collected call stack profiles.
     // |completed_callback| must be callable on any thread.
     SamplingThread(std::unique_ptr<NativeStackSampler> native_sampler,
                    const SamplingParams& params,
@@ skipping 22 matching lines @@
 
     // If Stop() is called, it signals this event to force the sampling to
     // terminate before all the samples specified in |params_| are collected.
     WaitableEvent stop_event_;
 
     const CompletedCallback completed_callback_;
 
     DISALLOW_COPY_AND_ASSIGN(SamplingThread);
   };
 
+  // Adds "phases" and "activities" annotations to a Sample.
+  static void RecordAnnotations(Sample* sample);
+
+  // These global variables hold current system state. These values are
+  // recorded with every captured sample, done on a separate thread which is
+  // why updates to these must be atomic. A PostTask to move the the updates
+  // to that thread would skew the timing and a lock could result in deadlock
+  // if the thread making a change was also being profiled and got stopped.
+  static subtle::Atomic32 process_phases_;
+  static subtle::Atomic32 current_activities_;
+
   // The thread whose stack will be sampled.
   PlatformThreadId thread_id_;
 
   const SamplingParams params_;
 
   std::unique_ptr<SamplingThread> sampling_thread_;
   PlatformThreadHandle sampling_thread_handle_;
 
   const CompletedCallback completed_callback_;
 
   // Stored until it can be passed to the NativeStackSampler created in Start().
   NativeStackSamplerTestDelegate* const test_delegate_;
 
   DISALLOW_COPY_AND_ASSIGN(StackSamplingProfiler);
 };
 
 // These operators permit types to be compared and used in a map of Samples, as
 // done in tests and by the metrics provider code.
 BASE_EXPORT bool operator==(const StackSamplingProfiler::Module& a,
                             const StackSamplingProfiler::Module& b);
+BASE_EXPORT bool operator==(const StackSamplingProfiler::Sample& a,
+                            const StackSamplingProfiler::Sample& b);
+BASE_EXPORT bool operator!=(const StackSamplingProfiler::Sample& a,
+                            const StackSamplingProfiler::Sample& b);
+BASE_EXPORT bool operator<(const StackSamplingProfiler::Sample& a,
+                           const StackSamplingProfiler::Sample& b);
 BASE_EXPORT bool operator==(const StackSamplingProfiler::Frame& a,
                             const StackSamplingProfiler::Frame& b);
 BASE_EXPORT bool operator<(const StackSamplingProfiler::Frame& a,
                            const StackSamplingProfiler::Frame& b);
 
 }  // namespace base
 
 #endif  // BASE_PROFILER_STACK_SAMPLING_PROFILER_H_