Record Chrome trace events in tcmalloc heap profiles

base/message_loop/message_loop.cc

 // Copyright 2013 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.
 
 #include "base/message_loop/message_loop.h"
 
 #include <algorithm>
 
 #include "base/bind.h"
 #include "base/compiler_specific.h"
@@ skipping 440 matching lines @@
   PendingTask pending_task = deferred_non_nestable_work_queue_.front();
   deferred_non_nestable_work_queue_.pop();
 
   RunTask(pending_task);
   return true;
 }
 
 void MessageLoop::RunTask(const PendingTask& pending_task) {
   TRACE_EVENT_FLOW_END0("task", "MessageLoop::PostTask",
       TRACE_ID_MANGLE(GetTaskTraceID(pending_task, this)));
-  TRACE_EVENT2("task", "MessageLoop::RunTask",
-               "src_file", pending_task.posted_from.file_name(),
-               "src_func", pending_task.posted_from.function_name());
+  // RunTask has special memory tracing needs. The file name where the task
+  // was posted is much more useful than "MessageLoop::RunTask" so we invoke

[nduca, 2013/06/20 20:09:29]

lets pull this out to another followup patch.. its a good one that merits some
focused thinking, hence the proposal to pull out.

[James Cook, 2013/06/29 00:02:42]

OK. I pulled this section out.

+  // the tracing macros separately with different strings.
+  // TODO(jamescook): Use TRACE_MEMORY2 here when it is implemented.
+  TRACE_MEMORY("task", pending_task.posted_from.file_name());
+  INTERNAL_TRACE_EVENT_ADD_SCOPED("task", "MessageLoop::RunTask",

[dsinclair, 2013/06/18 15:30:15]

This makes me sad. If we're going to be using it outside of the trace_event
files we should rename it to no longer be INTERNAL_.

If this seems like something we'll do often, what about doing a:

TRACE_EVENT_NO_MEMORY0,1,2?

Then TRACE_EVENT0 just becomes
TRACE_MEMORY() \
TRACE_EVENT_NO_MEMORY0

etc.

[James Cook, 2013/06/29 00:02:42]

Yeah. The only reason this was here was to support the hack above to get the
file_name() of the posted task.  We probably won't need access to
INTERNAL_TRACE_EVENT if I can build TRACE_MEMORY1,2 etc. and record multiple
items.

+      "src_file", pending_task.posted_from.file_name(),
+      "src_func", pending_task.posted_from.function_name());
   DCHECK(nestable_tasks_allowed_);
   // Execute the task and assume the worst: It is probably not reentrant.
   nestable_tasks_allowed_ = false;
 
   // Before running the task, store the program counter where it was posted
   // and deliberately alias it to ensure it is on the stack if the task
   // crashes. Be careful not to assume that the variable itself will have the
   // expected value when displayed by the optimizer in an optimized build.
   // Look at a memory dump of the stack.
   const void* program_counter =
@@ skipping 351 matching lines @@
       fd,
       persistent,
       mode,
       controller,
       delegate);
 }
 
 #endif
 
 }  // namespace base