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/*
* Copyright (C) 2012 Google Inc. All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY APPLE INC. AND ITS CONTRIBUTORS ``AS IS'' AND ANY
* EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
* WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
* DISCLAIMED. IN NO EVENT SHALL APPLE INC. OR ITS CONTRIBUTORS BE LIABLE FOR ANY
* DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
* (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
* LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON
* ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
* SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
#include "config.h"
#if USE(ACCELERATED_COMPOSITING)
#include "CCFrameRateCounter.h"
#include "CCProxy.h"
#include <public/Platform.h>
#include <wtf/CurrentTime.h>
namespace WebCore {
const double CCFrameRateCounter::kFrameTooFast = 1.0 / 70.0; // measured in seconds
const double CCFrameRateCounter::kFrameTooSlow = 1.0 / 12.0;
// safeMod works on -1, returning m-1 in that case.
static inline int safeMod(int number, int modulus)
{
return (number + modulus) % modulus;
}
inline int CCFrameRateCounter::frameIndex(int frame) const
{
return safeMod(frame, kTimeStampHistorySize);
}
CCFrameRateCounter::CCFrameRateCounter()
: m_currentFrameNumber(1)
{
m_timeStampHistory[0] = currentTime();
m_timeStampHistory[1] = m_timeStampHistory[0];
for (int i = 2; i < kTimeStampHistorySize; i++)
m_timeStampHistory[i] = 0;
}
void CCFrameRateCounter::markBeginningOfFrame(double timestamp)
{
if (CCProxy::hasImplThread() && m_currentFrameNumber > 0) {
double lastFrameTimestamp = frameIndex(m_currentFrameNumber - 1);
double drawDelaySeconds = timestamp - lastFrameTimestamp;
double drawDelayMs = drawDelaySeconds * 1000.0;
WebKit::Platform::current()->histogramCustomCounts("Renderer4.CompositorThreadImplDrawDelay", static_cast<int>(drawDelayMs), 1, 120, 60);
}
m_timeStampHistory[frameIndex(m_currentFrameNumber)] = timestamp;
}
void CCFrameRateCounter::markEndOfFrame()
{
m_currentFrameNumber += 1;
}
bool CCFrameRateCounter::isBadFrameInterval(double intervalBetweenConsecutiveFrames) const
{
bool schedulerAllowsDoubleFrames = !CCProxy::hasImplThread();
bool intervalTooFast = schedulerAllowsDoubleFrames && intervalBetweenConsecutiveFrames < kFrameTooFast;
bool intervalTooSlow = intervalBetweenConsecutiveFrames > kFrameTooSlow;
return intervalTooFast || intervalTooSlow;
}
bool CCFrameRateCounter::isBadFrame(int frameNumber) const
{
double delta = m_timeStampHistory[frameIndex(frameNumber)] -
m_timeStampHistory[frameIndex(frameNumber - 1)];
return isBadFrameInterval(delta);
}
void CCFrameRateCounter::getAverageFPSAndStandardDeviation(double& averageFPS, double& standardDeviation) const
{
int frame = m_currentFrameNumber - 1;
averageFPS = 0;
int averageFPSCount = 0;
double fpsVarianceNumerator = 0;
// Walk backwards through the samples looking for a run of good frame
// timings from which to compute the mean and standard deviation.
//
// 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.
//
// isBadFrame encapsulates the frame too slow/frame too fast logic.
while (1) {
if (!isBadFrame(frame)) {
averageFPSCount++;
double secForLastFrame = m_timeStampHistory[frameIndex(frame)] -
m_timeStampHistory[frameIndex(frame - 1)];
double x = 1.0 / secForLastFrame;
double deltaFromAverage = x - averageFPS;
// Change with caution - numerics. http://en.wikipedia.org/wiki/Standard_deviation
averageFPS = averageFPS + deltaFromAverage / averageFPSCount;
fpsVarianceNumerator = fpsVarianceNumerator + deltaFromAverage * (x - averageFPS);
}
if (averageFPSCount && isBadFrame(frame)) {
// We've gathered a run of good samples, so stop.
break;
}
--frame;
if (frameIndex(frame) == frameIndex(m_currentFrameNumber) || frame < 0) {
// We've gone through all available historical data, so stop.
break;
}
}
standardDeviation = sqrt(fpsVarianceNumerator / averageFPSCount);
}
double CCFrameRateCounter::timeStampOfRecentFrame(int n)
{
ASSERT(n >= 0 && n < kTimeStampHistorySize);
int desiredIndex = (frameIndex(m_currentFrameNumber) + n) % kTimeStampHistorySize;
return m_timeStampHistory[desiredIndex];
}
} // namespace WebCore
#endif // USE(ACCELERATED_COMPOSITING)
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