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 291 matching lines @@
       buffers_state.total_bytes() + frames * params_.GetBytesPerFrame());
 
   silence_detector_->Scan(dest, frames);
 
   AllowEntryToOnMoreIOData();
   return frames;
 }
 
 void AudioOutputController::WaitTillDataReady() {
   // Most of the time the data is ready already.
-  if (sync_reader_->DataReady())
+  bool ready = sync_reader_->DataReady();
+  UMA_HISTOGRAM_BOOLEAN("Media.AudioOutputController.DataReady", ready);

[DaleCurtis, 2013/05/29 18:27:46]

Instead of adding this new statistic we should fix the stat that's already
recorded in AudioSyncReader since it records the same thing. It's off currently
since we always call WaitTillDataReady() here which AudioSyncReader doesn't know
about.

Ideally I'd like to see all of this waiting code moved into AudioSyncReader and
the WaitTillDataReady() interface method removed. There's one use case which
makes this tricky though: Virtual streams.

You don't have to do this in this CL, but I'd rather not add this new stat in
favor of fixing the old one. I'll take some time to fix that up this week.

[DaveMoore, 2013/05/29 18:33:03]

Done.

+  if (ready)
     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",
+  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