[tracing] Adding task information to heap profiler

base/trace_event/heap_profiler_allocation_context_tracker.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_TRACE_EVENT_HEAP_PROFILER_ALLOCATION_CONTEXT_TRACKER_H_
 #define BASE_TRACE_EVENT_HEAP_PROFILER_ALLOCATION_CONTEXT_TRACKER_H_
 
 #include <vector>
 
 #include "base/atomicops.h"
@@ skipping 40 matching lines @@
   // Set the thread name in the AllocationContextTracker of current thread if
   // capture is enabled.
   static void SetCurrentThreadName(const char* name);
 
   // Pushes a frame onto the thread-local pseudo stack.
   void PushPseudoStackFrame(StackFrame frame);
 
   // Pops a frame from the thread-local pseudo stack.
   void PopPseudoStackFrame(StackFrame frame);
 
+  // Push and pop current task's context. A stack is used to support nested
+  // tasks and the top of the stack will be used in allocation context.
+  void PushCurrentTaskContext(const char* context);

[Primiano Tucci (use gerrit), 2016/03/31 15:37:16]

I aware about the fact that I am a real pain on naming.
Since this is either a task name or file path (don't remember which ATM) why
don't we make it explicit?
"context" makes it cryptic to understand what it really is.
It's a string, should be straightforward to tell what the content of such string
is when looking at the code.

[ssid, 2016/03/31 16:02:49]

Yes but I feel this will be reused for some other reason very soon. That time
there will not be a need to rename it. For example if we want to add IPC names
as context instead of stack frame, or even add the posted function name instead
of file name, this can still be used. I could also add context like WebKit or
skia. Do you strongly prefer that I change it to task_posted_file_name?

[Primiano Tucci (use gerrit), 2016/03/31 16:10:59]

Ahh ok, if you have upcoming use cases in mind it's ok leaving it as it is (but
then you have to figure out something below in the logic that strips the paths)

[ssid, 2016/04/01 04:34:54]

I changed the comment and function name. wdyt?

[Primiano Tucci (use gerrit), 2016/04/01 08:36:16]

Much better, thanks.

+  void PopCurrentTaskContext(const char* context);
+
   // Returns a snapshot of the current thread-local context.
   AllocationContext GetContextSnapshot();
 
   ~AllocationContextTracker();
 
  private:
   AllocationContextTracker();
 
   static subtle::Atomic32 capture_enabled_;
 
   // The pseudo stack where frames are |TRACE_EVENT| names.
   std::vector<StackFrame> pseudo_stack_;
 
   // The thread name is used as the first entry in the pseudo stack.
   const char* thread_name_;
 
+  // Stack of tasks' contexts. Context serves as a different dimension than
+  // pseudo stack to study the heap.

[Primiano Tucci (use gerrit), 2016/03/31 15:37:16]

s/to study the heap/to cluster allocations/

[ssid, 2016/04/01 04:34:54]

Done.

+  std::vector<const char*> task_contexts_;
+
   DISALLOW_COPY_AND_ASSIGN(AllocationContextTracker);
 };
 
 }  // namespace trace_event
 }  // namespace base
 
 #endif  // BASE_TRACE_EVENT_HEAP_PROFILER_ALLOCATION_CONTEXT_TRACKER_H_