StackSamplingProfiler: collect partial bursts if the profiler is stopped early

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>
 
@@ skipping 33 matching lines @@
 //   profiler.Start();
 //   // ... work being done on the target thread here ...
 //   profiler.Stop();  // optional, stops collection before complete per params
 //
 // The default SamplingParams causes stacks to be recorded in a single burst at
 // a 10Hz interval for a total of 30 seconds. All of these parameters may be
 // altered as desired.
 //
 // When all call stack profiles are complete, or the profiler is stopped, the
 // completed callback is called from a thread created by the profiler with the
-// completed profiles. A profile is considered complete if all requested samples
-// were recorded for the profile (i.e. it was not stopped prematurely).
+// collected profiles.
 //
 // The results of the profiling are passed to the completed callback and consist
 // of a vector of CallStackProfiles. Each CallStackProfile corresponds to a
 // burst as specified in SamplingParams and contains a set of Samples and
 // Modules. One Sample corresponds to a single recorded stack, and the Modules
 // record those modules associated with the recorded stack frames.
 class BASE_EXPORT StackSamplingProfiler {
  public:
   // Module represents the module (DLL or exe) corresponding to a stack frame.
   struct BASE_EXPORT Module {
@@ skipping 122 matching lines @@
                    const SamplingParams& params,
                    const CompletedCallback& completed_callback);
     ~SamplingThread() override;
 
     // PlatformThread::Delegate:
     void ThreadMain() override;
 
     void Stop();
 
    private:
-    // Collects a call stack profile from a single burst. Returns true if the
-    // profile was collected, or false if collection was stopped before it
-    // completed.
-    bool CollectProfile(CallStackProfile* profile, TimeDelta* elapsed_time);
+    // Collects |profile| from a single burst. If the profiler was stopped
+    // during collection, sets |was_stopped| and provides the set of samples
+    // collected up to that point.
+    void CollectProfile(CallStackProfile* profile, TimeDelta* elapsed_time,
+                        bool* was_stopped);
 
     // Collects call stack profiles from all bursts, or until the sampling is
-    // stopped. If stopped before complete, |call_stack_profiles| will contain
-    // only full bursts.
+    // stopped. If stopped before complete, the last profile in
+    // |call_stack_profiles| may contain a partial burst.
     void CollectProfiles(CallStackProfiles* profiles);
 
     scoped_ptr<NativeStackSampler> native_sampler_;
     const SamplingParams params_;
 
     // 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_;
@@ skipping 17 matching lines @@
 // The metrics provider code wants to put Samples in a map and compare them,
 // which requires us to define a few operators.
 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_