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 33 matching lines @@
 // completed callback is called from a thread created by the profiler with the
 // 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:
+  // These types are defined simply for clarity in places that define them
+  // (using this as the base type for an enum) and in methods that take them
+  // as parameters.
+  using ProcessPhase = int;
+  using ProcessActivity = int;

[Mike Wittman, 2016/11/02 17:14:39]

Can we avoid defining these typedefs and just use "int" in the interfaces? I
feel like these are a net negative for readability in that they don't add
information to the interfaces below, and they hide the type in use, forcing the
reader to refer back here to be able to fully understand the interfaces.

[bcwhite, 2016/11/02 20:10:45]

I had wanted to clearly define what is being passed.  But now that I've got the
constants generated in the .proto file, it has to be an "int" anyway.

+
   // Module represents the module (DLL or exe) corresponding to a stack frame.
   struct BASE_EXPORT Module {
     Module();
     Module(uintptr_t base_address,
            const std::string& id,
            const FilePath& filename);
     ~Module();
 
     // Points to the base address of the module.
     uintptr_t base_address;
@@ skipping 23 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.
+    uint32_t process_phases = 0;
+
+    // A bit-field indicating activities which were active when the frame was
+    // captured. See ProcessActivity, above.
+    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.

[Mike Wittman, 2016/11/02 17:14:39]

Document that the valid values are between 0 and 31.

[bcwhite, 2016/11/02 20:10:45]

Done.

+  static void SetProcessPhase(ProcessPhase phase);
+  static void RecordActivityBegin(ProcessActivity activity);
+  static void RecordActivityEnd(ProcessActivity activity);
+
  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_