Introducing phased profiling framework

components/metrics/profiler/tracking_synchronizer.cc

Index: components/metrics/profiler/tracking_synchronizer.cc
diff --git a/components/metrics/profiler/tracking_synchronizer.cc b/components/metrics/profiler/tracking_synchronizer.cc
index 8d53bd2a7ec19f42df2336cd968f5dcf49eb89b2..501b2cd409d521b03089335093591b1eb25b6ce5 100644
--- a/components/metrics/profiler/tracking_synchronizer.cc
+++ b/components/metrics/profiler/tracking_synchronizer.cc
@@ -9,6 +9,7 @@
 #include "base/threading/thread.h"
 #include "base/tracked_objects.h"
 #include "components/metrics/profiler/tracking_synchronizer_observer.h"
+#include "components/variations/variations_associated_data.h"
 #include "content/public/browser/browser_thread.h"
 #include "content/public/browser/profiler_controller.h"
 #include "content/public/common/process_type.h"
@@ -180,9 +181,11 @@ base::LazyInstance
 // TrackingSynchronizer methods and members.
 
 TrackingSynchronizer::TrackingSynchronizer()
-    : last_used_sequence_number_(kNeverUsableSequenceNumber) {
+    : last_used_sequence_number_(kNeverUsableSequenceNumber),
+      start_time_(base::TimeTicks::Now()) {
   DCHECK(!g_tracking_synchronizer);
   g_tracking_synchronizer = this;
+  phase_start_times_.push_back(base::TimeTicks::Now());
   content::ProfilerController::GetInstance()->Register(this);
 }
 
@@ -253,10 +256,10 @@ int TrackingSynchronizer::RegisterAndNotifyAllProcesses(
   // Get profiler data from renderer and browser child processes.
   content::ProfilerController::GetInstance()->GetProfilerData(sequence_number);
 
-  // Send profiler_data from browser process.
-  tracked_objects::ProcessDataSnapshot process_data;
-  tracked_objects::ThreadData::Snapshot(&process_data);
-  DecrementPendingProcessesAndSendData(sequence_number, process_data,
+  // Send process_data_snapshot from browser process.

[Alexei Svitkine (slow), 2015/03/09 17:13:35]

Nit: surround in |'s or remove _'s.

[vadimt, 2015/03/13 23:18:01]

Done.

+  tracked_objects::ProcessDataSnapshot process_data_snapshot;
+  tracked_objects::ThreadData::GetProcessDataSnapshot(&process_data_snapshot);
+  DecrementPendingProcessesAndSendData(sequence_number, process_data_snapshot,
                                        content::PROCESS_TYPE_BROWSER);
 
   return sequence_number;
@@ -273,8 +276,39 @@ void TrackingSynchronizer::DecrementPendingProcessesAndSendData(
     return;
 
   if (request->callback_object_.get()) {
-    request->callback_object_
-        ->ReceivedProfilerData(profiler_data, process_type);
+    // We are going to loop though past profiling phases and notify the request
+    // about each phase that is contained in profiler_data. past_profiler_events
+    // will track the set of past profiling events as we go.
+    ProfilerEventsSet past_profiler_events;
+
+    // Go though all completed phases, and though the current one. The current

[Ilya Sherman, 2015/03/10 00:48:10]

nit: "though" -> "through" (twice)

[vadimt, 2015/03/13 23:18:01]

Done.

+    // one is not in phase_completion_events_sequence_, but note the <=
+    // comparison.

[Alexei Svitkine (slow), 2015/03/09 17:13:35]

This logic seems sufficiently non trivial to warrant unit tests. Can you add
some?

[vadimt, 2015/03/13 23:18:01]

Done.

+    for (size_t phase = 0; phase <= phase_completion_events_sequence_.size();
+         ++phase) {
+      tracked_objects::PhasedProcessDataSnapshots::const_iterator it =
+          profiler_data.phased_process_data_snapshots.find(phase);
+
+      if (it != profiler_data.phased_process_data_snapshots.end()) {
+        // If the phase is contained in the received snapshot, notify the
+        // request.
+        const base::TimeDelta phase_start =
+            phase_start_times_[phase] - start_time_;
+        const base::TimeDelta phase_finish =
+            (phase + 1 < phase_start_times_.size()
+                 ? phase_start_times_[phase + 1]
+                 : base::TimeTicks::Now()) -
+            start_time_;
+        request->callback_object_->ReceivedProfilerData(
+            it->second, profiler_data.process_id, process_type, phase,
+            phase_start, phase_finish, past_profiler_events);
+      }
+
+      if (phase != phase_completion_events_sequence_.size()) {
+        past_profiler_events.push_back(
+            phase_completion_events_sequence_[phase]);
+      }
+    }
   }
 
   // Delete request if we have heard back from all child processes.