Introducing phased profiling framework

base/tracked_objects.h

Index: base/tracked_objects.h
diff --git a/base/tracked_objects.h b/base/tracked_objects.h
index 7840fecbd1459c10f551a83386b91d43f0e7eaeb..8193add7c9bdddb5b06ff44c3feece3d4fb7cb17 100644
--- a/base/tracked_objects.h
+++ b/base/tracked_objects.h
@@ -146,10 +146,14 @@ struct TrackingInfo;
 // TaskSnapshot instances, so that such instances can be sorted and
 // aggregated (and remain frozen during our processing).
 //
-// The ProcessDataSnapshot struct is a serialized representation of the list
-// of ThreadData objects for a process.  It holds a set of TaskSnapshots
-// and tracks parent/child relationships for the executed tasks.  The statistics
-// in a snapshot are gathered asynhcronously relative to their ongoing updates.
+// Profiling consists of phases. The concrete phase in the sequence of phases is
+// identified by its 0-based nubmer.
+//
+// The ProcessDataPhaseSnapshot struct is a serialized representation of the
+// list of ThreadData objects for a process for a concrete profiling phase. It
+// holds a set of TaskSnapshots and tracks parent/child relationships for the
+// executed tasks. The statistics in a snapshot are gathered asynhcronously
+// relative to their ongoing updates.
 // It is possible, though highly unlikely, that stats could be incorrectly
 // recorded by this process (all data is held in 32 bit ints, but we are not
 // atomically collecting all data, so we could have count that does not, for
@@ -240,6 +244,9 @@ class BASE_EXPORT Births: public BirthOnThread {
   // When we have a birth we update the count for this birthplace.
   void RecordBirth();
 
+  // Subtracts a value from the birth count.
+  void SubtractBirths(int count);
+
  private:
   // The number of births on this thread for our location_.
   int birth_count_;
@@ -277,7 +284,7 @@ class BASE_EXPORT DeathData {
   int32 queue_duration_max() const;
   int32 queue_duration_sample() const;
 
-  // Reset all tallies to zero. This is used as a hack on realtime data.
+  // Reset all tallies to zero.
   void Clear();
 
  private:
@@ -341,6 +348,11 @@ struct BASE_EXPORT TaskSnapshot {
 // We also have a linked list of ThreadData instances, and that list is used to
 // harvest data from all existing instances.
 
+struct ProcessDataPhaseSnapshot;
+// Map from profiling phase number to the process-wide snapshotted
+// representation of the list of ThreadData objects that died during the given
+// phase.
+typedef std::map<int, ProcessDataPhaseSnapshot> PhasedProcessDataSnapshots;
 struct ProcessDataSnapshot;
 class BASE_EXPORT TaskStopwatch;
 
@@ -358,7 +370,7 @@ class BASE_EXPORT ThreadData {
   };
 
   typedef std::map<Location, Births*> BirthMap;
-  typedef std::map<const Births*, DeathData> DeathMap;
+  typedef std::map<Births*, DeathData> DeathMap;
   typedef std::pair<const Births*, const Births*> ParentChildPair;
   typedef std::set<ParentChildPair> ParentChildSet;
   typedef std::stack<const Births*> ParentStack;
@@ -375,8 +387,15 @@ class BASE_EXPORT ThreadData {
   // This may return NULL if the system is disabled for any reason.
   static ThreadData* Get();
 
-  // Fills |process_data| with all the recursive results in our process.
-  static void Snapshot(ProcessDataSnapshot* process_data);
+  // Fills |process_data_snapshot| with phased snapshots of all profiling
+  // phases, including the currect one, identified by |current_profiling_phase|.

[Alexei Svitkine (slow), 2015/03/06 20:06:40]

Nit: currect -> current

I don't understand this.

Is the assumption here that this can only be called with
|current_profiling_phase| being the current phase? What happens if you call it
with a different value? Will it still be snapshots of all profiling phases?

Or is the only valid value the current one? If so, why require the caller to
pass it as a param? Can't the impl track which one is the last one internally?

[vadimt, 2015/03/06 21:34:58]

Correct. This must be the current profiler phase.
Imagine a renderer started after NonEmptyPaint event.
It doesn't know the last event, and cannot deduce whether it should return the
snapshot as belonging to phase 0 or 1.

+  static void GetProcessDataSnapshot(
+      int current_profiling_phase,
+      ProcessDataSnapshot* process_data_snapshot);
+
+  // Called when the current profiling phase, identified by |profiling_phase|,
+  // ends.
+  static void OnProfilingPhaseCompletion(int profiling_phase);
 
   // Finds (or creates) a place to count births from the given location in this
   // thread, and increment that tally.
@@ -402,16 +421,14 @@ class BASE_EXPORT ThreadData {
   // the task.
   // The |end_of_run| was just obtained by a call to Now() (just after the task
   // finished).
-  static void TallyRunOnWorkerThreadIfTracking(
-      const Births* birth,
-      const TrackedTime& time_posted,
-      const TaskStopwatch& stopwatch);
+  static void TallyRunOnWorkerThreadIfTracking(const TrackedTime& time_posted,
+                                               const TaskStopwatch& stopwatch,
+                                               Births* birth);
 
   // Record the end of execution in region, generally corresponding to a scope
   // being exited.
-  static void TallyRunInAScopedRegionIfTracking(
-      const Births* birth,
-      const TaskStopwatch& stopwatch);
+  static void TallyRunInAScopedRegionIfTracking(const TaskStopwatch& stopwatch,
+                                                Births* birth);
 
   const std::string& thread_name() const { return thread_name_; }
 
@@ -506,29 +523,41 @@ class BASE_EXPORT ThreadData {
   Births* TallyABirth(const Location& location);
 
   // Find a place to record a death on this thread.
-  void TallyADeath(const Births& birth,
-                   int32 queue_duration,
-                   const TaskStopwatch& stopwatch);
+  void TallyADeath(int32 queue_duration,
+                   const TaskStopwatch& stopwatch,
+                   Births* birth);
 
   // Snapshot (under a lock) the profiled data for the tasks in each ThreadData
   // instance.  Also updates the |birth_counts| tally for each task to keep
-  // track of the number of living instances of the task.
-  static void SnapshotAllExecutedTasks(ProcessDataSnapshot* process_data,
-                                       BirthCountMap* birth_counts);
+  // track of the number of living instances of the task. If |reset| is true,
+  // remove all recorded deaths.
+  static void SnapshotAllExecutedTasks(
+      bool reset,
+      ProcessDataPhaseSnapshot* process_data_phase,
+      BirthCountMap* birth_counts);
+
+  // Fills |process_data_phase| with all the recursive results in our process.
+  // If |reset| is true, remove all recorded deaths.
+  static void Snapshot(bool reset,
+                       ProcessDataPhaseSnapshot* process_data_phase);
 
   // Snapshots (under a lock) the profiled data for the tasks for this thread
   // and writes all of the executed tasks' data -- i.e. the data for the tasks
-  // with with entries in the death_map_ -- into |process_data|.  Also updates
-  // the |birth_counts| tally for each task to keep track of the number of
-  // living instances of the task -- that is, each task maps to the number of
-  // births for the task that have not yet been balanced by a death.
-  void SnapshotExecutedTasks(ProcessDataSnapshot* process_data,
+  // with with entries in the death_map_ -- into |process_data_phase|.  Also
+  // updates the |birth_counts| tally for each task to keep track of the number
+  // of living instances of the task -- that is, each task maps to the number of
+  // births for the task that have not yet been balanced by a death. If |reset|
+  // is true, remove all recorded deaths.
+  void SnapshotExecutedTasks(bool reset,
+                             ProcessDataPhaseSnapshot* process_data_phase,
                              BirthCountMap* birth_counts);
 
   // Using our lock, make a copy of the specified maps.  This call may be made
   // on  non-local threads, which necessitate the use of the lock to prevent
-  // the map(s) from being reallocated while they are copied.
-  void SnapshotMaps(BirthMap* birth_map,
+  // the map(s) from being reallocated while they are copied. If |reset| is
+  // true, remove all recorded deaths.
+  void SnapshotMaps(bool reset,
+                    BirthMap* birth_map,
                     DeathMap* death_map,
                     ParentChildSet* parent_child_set);
 
@@ -596,6 +625,10 @@ class BASE_EXPORT ThreadData {
   // We set status_ to SHUTDOWN when we shut down the tracking service.
   static Status status_;
 
+  // Process data snapshots for completed profiling phases.
+  static base::LazyInstance<PhasedProcessDataSnapshots>
+      completed_phases_snapshots_;
+
   // Link to next instance (null terminated list). Used to globally track all
   // registered instances (corresponds to all registered threads where we keep
   // data).
@@ -746,15 +779,28 @@ struct BASE_EXPORT ParentChildPairSnapshot {
 };
 
 //------------------------------------------------------------------------------
-// A snapshotted representation of the list of ThreadData objects for a process.
+// A snapshotted representation of the list of ThreadData objects for a process,
+// for a single profiling phase.
+
+struct BASE_EXPORT ProcessDataPhaseSnapshot {
+ public:
+  ProcessDataPhaseSnapshot();
+  ~ProcessDataPhaseSnapshot();
+
+  std::vector<TaskSnapshot> tasks;
+  std::vector<ParentChildPairSnapshot> descendants;
+};
+
+//------------------------------------------------------------------------------
+// A snapshotted representation of the list of ThreadData objects for a process,
+// for all profiling phases, including the current one.
 
 struct BASE_EXPORT ProcessDataSnapshot {
  public:
   ProcessDataSnapshot();
   ~ProcessDataSnapshot();
 
-  std::vector<TaskSnapshot> tasks;
-  std::vector<ParentChildPairSnapshot> descendants;
+  PhasedProcessDataSnapshots phased_process_data_snapshots;
   int process_id;
 };