[tracing] Adding task information to heap profiler

base/trace_event/trace_event.h

Index: base/trace_event/trace_event.h
diff --git a/base/trace_event/trace_event.h b/base/trace_event/trace_event.h
index 2321d7ad62bd66c38653ab49b5d28e664b8a861d..1ee1fb4346244f814733e73c52c3f712554db8f3 100644
--- a/base/trace_event/trace_event.h
+++ b/base/trace_event/trace_event.h
@@ -18,6 +18,7 @@
 #include "base/macros.h"
 #include "base/time/time.h"
 #include "base/trace_event/common/trace_event_common.h"
+#include "base/trace_event/heap_profiler_allocation_context_tracker.h"
 #include "base/trace_event/trace_event_system_stats_monitor.h"
 #include "base/trace_event/trace_log.h"
 #include "build/build_config.h"
@@ -382,6 +383,15 @@ TRACE_EVENT_API_CLASS_EXPORT extern \
   INTERNAL_TRACE_EVENT_UID(ScopedContext)                                  \
   INTERNAL_TRACE_EVENT_UID(scoped_context)(context.raw_id());
 
+// Special trace event macro to trace task execution with the location where it
+// was posted from.
+#define TRACE_TASK_EXECUTION(run_function, task)           \

[oystein (OOO til 10th of July), 2016/03/29 21:28:35]

I don't think this belongs in trace_event.h; typically that file should have
implementation code and pure macros should be in trace_event_common.h. I would
keep ScopedTaskExecutionEvent there and add a define for it (like
TRACE_EVENT_API_SCOPED_TASK_EXECUTION_EVENT) and move TRACE_TASK_EXECUTION to
trace_event_common.h. 

[ssid, 2016/03/29 23:04:19]

Thanks I was really confused about trace_event.h and trace_event_common.h.
I have added an INTERNAL macro instead of API since I am not planning to use
this api otherwise. Did I get it correct?

[oystein (OOO til 10th of July), 2016/03/29 23:44:52]

Almost! I mainly don't think trace_event.h should have the macro at all, for
consistency (trace_event.h should be as minimal as possible and not contain 
stuff like hardcoded categories).

I'd rather do, in trace_event.h (instead of the macro):
#define INTERNAL_TRACE_SCOPED_TASK_EXECUTION_EVENT
trace_event_internal::ScopedTaskExecutionEvent

and then the macro in trace_event_common.h would be something like this:
#define TRACE_TASK_EXECUTION(run_function, task)            \
  TRACE_EVENT2("toplevel", run_function, "src_file",                       \
               task.posted_from.file_name(), "src_func",                   \
               task.posted_from.function_name());                          \
  INTERNAL_TRACE_SCOPED_TASK_EXECUTION_EVENT INTERNAL_TRACE_EVENT_UID( \
       task_event)(task.posted_from.file_name());

+  TRACE_EVENT2("toplevel", (run_function), "src_file",     \

[oystein (OOO til 10th of July), 2016/03/29 21:28:35]

Why are the parameter usages all wrapped by ()? We don't do that elsewhere, but
maybe there's some reason I'm missing for it :).

[ssid, 2016/03/29 23:04:19]

Ah, it existed in the other file and I had copied it. It isn't required,
removed.

+               (task).posted_from.file_name(), "src_func", \
+               (task).posted_from.function_name());        \
+  trace_event_internal::ScopedTaskExecutionEvent event(    \

[oystein (OOO til 10th of July), 2016/03/29 21:28:35]

INTERNAL_TRACE_EVENT_UID(event) to avoid conflicts with 'event' vars in code
using this.

[ssid, 2016/03/29 23:04:19]

Done.

+      (task).posted_from.file_name());
+
 namespace trace_event_internal {
 
 // Specify these values when the corresponding argument of AddTraceEvent is not
@@ -1045,6 +1055,30 @@ class TraceEventSamplingStateScope {
   const char* previous_state_;
 };
 
+// ScopedTaskExecutionEvent records the current task's context in the heap
+// profiler.
+class ScopedTaskExecutionEvent {
+ public:
+  ScopedTaskExecutionEvent(const char* task_context) : context_(task_context) {
+    if (UNLIKELY(
+            base::trace_event::AllocationContextTracker::capture_enabled())) {
+      base::trace_event::AllocationContextTracker::GetInstanceForCurrentThread()
+          ->PushCurrentTaskContext(context_);
+    }
+  }
+
+  ~ScopedTaskExecutionEvent() {
+    if (UNLIKELY(
+            base::trace_event::AllocationContextTracker::capture_enabled())) {
+      base::trace_event::AllocationContextTracker::GetInstanceForCurrentThread()
+          ->PopCurrentTaskContext(context_);
+    }
+  }
+
+ private:
+  const char* context_;
+};
+
 }  // namespace trace_event_internal
 
 namespace base {