Reduce wait time for Windows in AudioOutputController:WaitTillDataReady()

media/audio/audio_output_controller.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 "media/audio/audio_output_controller.h"
 
 #include "base/bind.h"
 #include "base/debug/trace_event.h"
 #include "base/message_loop.h"
 #include "base/metrics/histogram.h"
@@ skipping 295 matching lines @@
   AllowEntryToOnMoreIOData();
   return frames;
 }
 
 void AudioOutputController::WaitTillDataReady() {
   // Most of the time the data is ready already.
   if (sync_reader_->DataReady())
     return;
 
   base::TimeTicks start = base::TimeTicks::Now();
+  const base::TimeDelta kMaxWait = base::TimeDelta::FromMilliseconds(20);
 #if defined(OS_WIN)
-  // Wait for up to 683ms for DataReady().  683ms was chosen because it's larger
-  // than the playback time of the WaveOut buffer size using the minimum
-  // supported sample rate: 2048 / 3000 = ~683ms.
-  // TODO(davemoore): We think this can be reduced to 20ms based on
-  // http://crrev.com/180102 but will do that in separate cl for mergability.
-  const base::TimeDelta kMaxWait = base::TimeDelta::FromMilliseconds(683);
+  // Sleep(0) on windows lets the other threads run.
   const base::TimeDelta kSleep = base::TimeDelta::FromMilliseconds(0);
 #else
-  const base::TimeDelta kMaxWait = base::TimeDelta::FromMilliseconds(20);
   // We want to sleep for a bit here, as otherwise a backgrounded renderer won't
   // get enough cpu to send the data and the high priority thread in the browser
   // will use up a core causing even more skips.
   const base::TimeDelta kSleep = base::TimeDelta::FromMilliseconds(2);
 #endif
   base::TimeDelta time_since_start;
   do {
     base::PlatformThread::Sleep(kSleep);
     time_since_start = base::TimeTicks::Now() - start;
   } while (!sync_reader_->DataReady() && (time_since_start < kMaxWait));
-  UMA_HISTOGRAM_CUSTOM_TIMES("Media.AudioOutputControllerDataNotReady",

[DaleCurtis, 2013/05/29 21:39:06]

Actually, you can revert the histogram change too. I've got a CL close to finish
which moves this statistic into AudioSyncReader, so it won't be able to use the
AudioOutputController group.  Here's my WIP CL which merges this one in for now.

+  UMA_HISTOGRAM_CUSTOM_TIMES("Media.AudioOutputController.WaitForDataTime",
                              time_since_start,
                              base::TimeDelta::FromMilliseconds(1),
                              base::TimeDelta::FromMilliseconds(1000),
                              50);
 }
 
 void AudioOutputController::OnError(AudioOutputStream* stream) {
   // Handle error on the audio controller thread.
   message_loop_->PostTask(FROM_HERE, base::Bind(
       &AudioOutputController::DoReportError, this));
@@ skipping 95 matching lines @@
   DCHECK(base::AtomicRefCountIsZero(&num_allowed_io_));
   base::AtomicRefCountInc(&num_allowed_io_);
 }
 
 void AudioOutputController::DisallowEntryToOnMoreIOData() {
   const bool is_zero = !base::AtomicRefCountDec(&num_allowed_io_);
   DCHECK(is_zero);
 }
 
 }  // namespace media