Add TRACE_EVENT macros to net.

net/url_request/url_request_http_job.cc

 // Copyright (c) 2012 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 "net/url_request/url_request_http_job.h"
 
 #include "base/base_switches.h"
 #include "base/bind.h"
 #include "base/bind_helpers.h"
 #include "base/command_line.h"
 #include "base/compiler_specific.h"
 #include "base/file_version_info.h"
 #include "base/location.h"
 #include "base/macros.h"
 #include "base/metrics/field_trial.h"
 #include "base/metrics/histogram_macros.h"
 #include "base/profiler/scoped_tracker.h"
 #include "base/rand_util.h"
 #include "base/single_thread_task_runner.h"
 #include "base/strings/string_util.h"
 #include "base/thread_task_runner_handle.h"
 #include "base/time/time.h"
+#include "base/trace_event/trace_event.h"
 #include "base/values.h"
 #include "net/base/host_port_pair.h"
 #include "net/base/load_flags.h"
 #include "net/base/net_errors.h"
 #include "net/base/network_delegate.h"
 #include "net/base/network_quality_estimator.h"
 #include "net/base/registry_controlled_domains/registry_controlled_domain.h"
 #include "net/base/sdch_manager.h"
 #include "net/base/sdch_net_log_params.h"
 #include "net/base/url_util.h"
@@ skipping 1022 matching lines @@
 void URLRequestHttpJob::OnHeadersReceivedCallback(int result) {
   awaiting_callback_ = false;
 
   // Check that there are no callbacks to already canceled requests.
   DCHECK_NE(URLRequestStatus::CANCELED, GetStatus().status());
 
   SaveCookiesAndNotifyHeadersComplete(result);
 }
 
 void URLRequestHttpJob::OnReadCompleted(int result) {
+  TRACE_EVENT0("net", "URLRequestHttpJob::OnReadCompleted");

[mmenke, 2016/03/28 20:46:51]

What do you expect to do with the information you get here?  The covers the
filters, passing data to the embedder, and the whatever the embedder does with
the data...But it only covers the case the read completes asynchronously, and
doesn't cover when the filters or embedder does the exact same thing for
non-HTTP requests.  I suggest more targetted tracing.

[ssid, 2016/03/29 00:33:06]

I am expecting that this data is useful to understand where the memory
allocations are coming from. At least it could tell that the allocation is
related to http request in some way.
I was also hoping that Nick and Charles who have more context about the code
will help me making this complete.
cbentzel@ suggested to ask them.

I am working with statistics for adding trace events rather than  understanding
what are all the possible codepaths possible. I did try with lots of websites
and it turns out that case of read completing asynchronously was allocating more
memory than other cases. I tried to read similar functions in each folder and
add events there as well.

I don't understand when you say more targeted tracing. Do you mean I should add
more trace events in each of these components so that the data is complete? If
so, can you propose a way for me to find points to make this instrumentation
complete.

If I can contact one person in each sub-team of networking and point out these
"important" functions that would be great. I am trying to add trace events based
on statistically large memory using functions.
Can you please suggest any other alternative?

   read_in_progress_ = false;
 
   DCHECK_NE(ERR_IO_PENDING, result);
 
   if (ShouldFixMismatchedContentLength(result))
     result = OK;
 
   // EOF or error, done with this job.
   if (result <= 0)
     DoneWithRequest(FINISHED);
@@ skipping 554 matching lines @@
   return override_response_headers_.get() ?
              override_response_headers_.get() :
              transaction_->GetResponseInfo()->headers.get();
 }
 
 void URLRequestHttpJob::NotifyURLRequestDestroyed() {
   awaiting_callback_ = false;
 }
 
 }  // namespace net