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// Copyright 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 "cc/frame_rate_counter.h"
#include <limits>
#include "base/metrics/histogram.h"
#include "cc/proxy.h"
namespace cc {
const double FrameRateCounter::kFrameTooFast = 1.0 / 70.0; // measured in seconds
const double FrameRateCounter::kFrameTooSlow = 1.0 / 4.0;
const double FrameRateCounter::kDroppedFrameTime = 1.0 / 50.0;
// static
scoped_ptr<FrameRateCounter> FrameRateCounter::create(bool hasImplThread) {
return make_scoped_ptr(new FrameRateCounter(hasImplThread));
}
inline base::TimeDelta FrameRateCounter::recentFrameInterval(size_t n) const
{
DCHECK(n > 0);
return m_ringBuffer.ReadBuffer(n) - m_ringBuffer.ReadBuffer(n - 1);
}
FrameRateCounter::FrameRateCounter(bool hasImplThread)
: m_hasImplThread(hasImplThread)
, m_droppedFrameCount(0)
{
}
void FrameRateCounter::saveTimeStamp(base::TimeTicks timestamp)
{
m_ringBuffer.SaveToBuffer(timestamp);
// Check if frame interval can be computed.
if (m_ringBuffer.CurrentIndex() < 2)
return;
base::TimeDelta frameIntervalSeconds = recentFrameInterval(m_ringBuffer.BufferSize() - 1);
if (m_hasImplThread && m_ringBuffer.CurrentIndex() > 0) {
UMA_HISTOGRAM_CUSTOM_COUNTS("Renderer4.CompositorThreadImplDrawDelay",
frameIntervalSeconds.InMilliseconds(),
1, 120, 60);
}
if (!isBadFrameInterval(frameIntervalSeconds) &&
frameIntervalSeconds.InSecondsF() > kDroppedFrameTime)
++m_droppedFrameCount;
}
bool FrameRateCounter::isBadFrameInterval(base::TimeDelta intervalBetweenConsecutiveFrames) const
{
double delta = intervalBetweenConsecutiveFrames.InSecondsF();
bool schedulerAllowsDoubleFrames = !m_hasImplThread;
bool intervalTooFast = schedulerAllowsDoubleFrames ? delta < kFrameTooFast : delta <= 0.0;
bool intervalTooSlow = delta > kFrameTooSlow;
return intervalTooFast || intervalTooSlow;
}
void FrameRateCounter::getMinAndMaxFPS(double& minFPS, double& maxFPS) const
{
minFPS = std::numeric_limits<double>::max();
maxFPS = 0;
for (size_t i = m_ringBuffer.BufferSize() - 1; i > 0 && m_ringBuffer.IsFilledIndex(i - 1); --i) {
base::TimeDelta delta = recentFrameInterval(i);
if (isBadFrameInterval(delta))
continue;
DCHECK(delta.InSecondsF() > 0);
double fps = 1.0 / delta.InSecondsF();
minFPS = std::min(fps, minFPS);
maxFPS = std::max(fps, maxFPS);
}
if (minFPS > maxFPS)
minFPS = maxFPS;
}
double FrameRateCounter::getAverageFPS() const
{
int frameCount = 0;
double frameTimesTotal = 0;
double averageFPS = 0;
// Walk backwards through the samples looking for a run of good frame
// timings from which to compute the mean.
//
// Slow frames occur just because the user is inactive, and should be
// ignored. Fast frames are ignored if the scheduler is in single-thread
// mode in order to represent the true frame rate in spite of the fact that
// the first few swapbuffers happen instantly which skews the statistics
// too much for short lived animations.
//
// isBadFrameInterval encapsulates the frame too slow/frame too fast logic.
for (size_t i = m_ringBuffer.BufferSize() - 1; i > 0 && m_ringBuffer.IsFilledIndex(i - 1) && frameTimesTotal < 1.0; --i) {
base::TimeDelta delta = recentFrameInterval(i);
if (!isBadFrameInterval(delta)) {
frameCount++;
frameTimesTotal += delta.InSecondsF();
} else if (frameCount)
break;
}
if (frameCount) {
DCHECK(frameTimesTotal > 0);
averageFPS = frameCount / frameTimesTotal;
}
return averageFPS;
}
base::TimeTicks FrameRateCounter::timeStampOfRecentFrame(size_t n) const
{
DCHECK(n < m_ringBuffer.BufferSize());
if (m_ringBuffer.IsFilledIndex(n))
return m_ringBuffer.ReadBuffer(n);
return base::TimeTicks();
}
} // namespace cc
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