replicant-frameworks_native/services/surfaceflinger/DispSync.cpp

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/*
* Copyright (C) 2013 The Android Open Source Project
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
#define ATRACE_TAG ATRACE_TAG_GRAPHICS
// This is needed for stdint.h to define INT64_MAX in C++
#define __STDC_LIMIT_MACROS
#include <math.h>
#include <cutils/log.h>
#include <ui/Fence.h>
#include <utils/String8.h>
#include <utils/Thread.h>
#include <utils/Trace.h>
#include <utils/Vector.h>
#include "DispSync.h"
#include "EventLog/EventLog.h"
namespace android {
// Setting this to true enables verbose tracing that can be used to debug
// vsync event model or phase issues.
static const bool kTraceDetailedInfo = false;
// This is the threshold used to determine when hardware vsync events are
// needed to re-synchronize the software vsync model with the hardware. The
// error metric used is the mean of the squared difference between each
// present time and the nearest software-predicted vsync.
static const nsecs_t kErrorThreshold = 160000000000; // 400 usec squared
// This is the offset from the present fence timestamps to the corresponding
// vsync event.
static const int64_t kPresentTimeOffset = PRESENT_TIME_OFFSET_FROM_VSYNC_NS;
class DispSyncThread: public Thread {
public:
DispSyncThread():
mStop(false),
mPeriod(0),
mPhase(0),
mWakeupLatency(0) {
}
virtual ~DispSyncThread() {}
void updateModel(nsecs_t period, nsecs_t phase) {
Mutex::Autolock lock(mMutex);
mPeriod = period;
mPhase = phase;
mCond.signal();
}
void stop() {
Mutex::Autolock lock(mMutex);
mStop = true;
mCond.signal();
}
virtual bool threadLoop() {
status_t err;
nsecs_t now = systemTime(SYSTEM_TIME_MONOTONIC);
nsecs_t nextEventTime = 0;
while (true) {
Vector<CallbackInvocation> callbackInvocations;
nsecs_t targetTime = 0;
{ // Scope for lock
Mutex::Autolock lock(mMutex);
if (mStop) {
return false;
}
if (mPeriod == 0) {
err = mCond.wait(mMutex);
if (err != NO_ERROR) {
ALOGE("error waiting for new events: %s (%d)",
strerror(-err), err);
return false;
}
continue;
}
nextEventTime = computeNextEventTimeLocked(now);
targetTime = nextEventTime;
bool isWakeup = false;
if (now < targetTime) {
err = mCond.waitRelative(mMutex, targetTime - now);
if (err == TIMED_OUT) {
isWakeup = true;
} else if (err != NO_ERROR) {
ALOGE("error waiting for next event: %s (%d)",
strerror(-err), err);
return false;
}
}
now = systemTime(SYSTEM_TIME_MONOTONIC);
if (isWakeup) {
mWakeupLatency = ((mWakeupLatency * 63) +
(now - targetTime)) / 64;
if (mWakeupLatency > 500000) {
// Don't correct by more than 500 us
mWakeupLatency = 500000;
}
if (kTraceDetailedInfo) {
ATRACE_INT64("DispSync:WakeupLat", now - nextEventTime);
ATRACE_INT64("DispSync:AvgWakeupLat", mWakeupLatency);
}
}
callbackInvocations = gatherCallbackInvocationsLocked(now);
}
if (callbackInvocations.size() > 0) {
fireCallbackInvocations(callbackInvocations);
}
}
return false;
}
status_t addEventListener(nsecs_t phase, const sp<DispSync::Callback>& callback) {
Mutex::Autolock lock(mMutex);
for (size_t i = 0; i < mEventListeners.size(); i++) {
if (mEventListeners[i].mCallback == callback) {
return BAD_VALUE;
}
}
EventListener listener;
listener.mPhase = phase;
listener.mCallback = callback;
// We want to allow the firstmost future event to fire without
// allowing any past events to fire. Because
// computeListenerNextEventTimeLocked filters out events within a half
// a period of the last event time, we need to initialize the last
// event time to a half a period in the past.
listener.mLastEventTime = systemTime(SYSTEM_TIME_MONOTONIC) - mPeriod / 2;
mEventListeners.push(listener);
mCond.signal();
return NO_ERROR;
}
status_t removeEventListener(const sp<DispSync::Callback>& callback) {
Mutex::Autolock lock(mMutex);
for (size_t i = 0; i < mEventListeners.size(); i++) {
if (mEventListeners[i].mCallback == callback) {
mEventListeners.removeAt(i);
mCond.signal();
return NO_ERROR;
}
}
return BAD_VALUE;
}
// This method is only here to handle the kIgnorePresentFences case.
bool hasAnyEventListeners() {
Mutex::Autolock lock(mMutex);
return !mEventListeners.empty();
}
private:
struct EventListener {
nsecs_t mPhase;
nsecs_t mLastEventTime;
sp<DispSync::Callback> mCallback;
};
struct CallbackInvocation {
sp<DispSync::Callback> mCallback;
nsecs_t mEventTime;
};
nsecs_t computeNextEventTimeLocked(nsecs_t now) {
nsecs_t nextEventTime = INT64_MAX;
for (size_t i = 0; i < mEventListeners.size(); i++) {
nsecs_t t = computeListenerNextEventTimeLocked(mEventListeners[i],
now);
if (t < nextEventTime) {
nextEventTime = t;
}
}
return nextEventTime;
}
Vector<CallbackInvocation> gatherCallbackInvocationsLocked(nsecs_t now) {
Vector<CallbackInvocation> callbackInvocations;
nsecs_t ref = now - mPeriod;
for (size_t i = 0; i < mEventListeners.size(); i++) {
nsecs_t t = computeListenerNextEventTimeLocked(mEventListeners[i],
ref);
if (t < now) {
CallbackInvocation ci;
ci.mCallback = mEventListeners[i].mCallback;
ci.mEventTime = t;
callbackInvocations.push(ci);
mEventListeners.editItemAt(i).mLastEventTime = t;
}
}
return callbackInvocations;
}
nsecs_t computeListenerNextEventTimeLocked(const EventListener& listener,
nsecs_t ref) {
nsecs_t lastEventTime = listener.mLastEventTime;
if (ref < lastEventTime) {
ref = lastEventTime;
}
nsecs_t phase = mPhase + listener.mPhase;
nsecs_t t = (((ref - phase) / mPeriod) + 1) * mPeriod + phase;
if (t - listener.mLastEventTime < mPeriod / 2) {
t += mPeriod;
}
return t;
}
void fireCallbackInvocations(const Vector<CallbackInvocation>& callbacks) {
for (size_t i = 0; i < callbacks.size(); i++) {
callbacks[i].mCallback->onDispSyncEvent(callbacks[i].mEventTime);
}
}
bool mStop;
nsecs_t mPeriod;
nsecs_t mPhase;
nsecs_t mWakeupLatency;
Vector<EventListener> mEventListeners;
Mutex mMutex;
Condition mCond;
};
class ZeroPhaseTracer : public DispSync::Callback {
public:
ZeroPhaseTracer() : mParity(false) {}
virtual void onDispSyncEvent(nsecs_t /*when*/) {
mParity = !mParity;
ATRACE_INT("ZERO_PHASE_VSYNC", mParity ? 1 : 0);
}
private:
bool mParity;
};
DispSync::DispSync() :
mRefreshSkipCount(0),
mThread(new DispSyncThread()) {
mThread->run("DispSync", PRIORITY_URGENT_DISPLAY + PRIORITY_MORE_FAVORABLE);
reset();
beginResync();
if (kTraceDetailedInfo) {
// If we're not getting present fences then the ZeroPhaseTracer
// would prevent HW vsync event from ever being turned off.
// Even if we're just ignoring the fences, the zero-phase tracing is
// not needed because any time there is an event registered we will
// turn on the HW vsync events.
if (!kIgnorePresentFences) {
addEventListener(0, new ZeroPhaseTracer());
}
}
}
DispSync::~DispSync() {}
void DispSync::reset() {
Mutex::Autolock lock(mMutex);
mNumResyncSamples = 0;
mFirstResyncSample = 0;
mNumResyncSamplesSincePresent = 0;
resetErrorLocked();
}
bool DispSync::addPresentFence(const sp<Fence>& fence) {
Mutex::Autolock lock(mMutex);
mPresentFences[mPresentSampleOffset] = fence;
mPresentTimes[mPresentSampleOffset] = 0;
mPresentSampleOffset = (mPresentSampleOffset + 1) % NUM_PRESENT_SAMPLES;
mNumResyncSamplesSincePresent = 0;
for (size_t i = 0; i < NUM_PRESENT_SAMPLES; i++) {
const sp<Fence>& f(mPresentFences[i]);
if (f != NULL) {
nsecs_t t = f->getSignalTime();
if (t < INT64_MAX) {
mPresentFences[i].clear();
mPresentTimes[i] = t + kPresentTimeOffset;
}
}
}
updateErrorLocked();
return mPeriod == 0 || mError > kErrorThreshold;
}
void DispSync::beginResync() {
Mutex::Autolock lock(mMutex);
mNumResyncSamples = 0;
}
bool DispSync::addResyncSample(nsecs_t timestamp) {
Mutex::Autolock lock(mMutex);
size_t idx = (mFirstResyncSample + mNumResyncSamples) % MAX_RESYNC_SAMPLES;
mResyncSamples[idx] = timestamp;
if (mNumResyncSamples < MAX_RESYNC_SAMPLES) {
mNumResyncSamples++;
} else {
mFirstResyncSample = (mFirstResyncSample + 1) % MAX_RESYNC_SAMPLES;
}
updateModelLocked();
if (mNumResyncSamplesSincePresent++ > MAX_RESYNC_SAMPLES_WITHOUT_PRESENT) {
resetErrorLocked();
}
if (kIgnorePresentFences) {
// If we don't have the sync framework we will never have
// addPresentFence called. This means we have no way to know whether
// or not we're synchronized with the HW vsyncs, so we just request
// that the HW vsync events be turned on whenever we need to generate
// SW vsync events.
return mThread->hasAnyEventListeners();
}
return mPeriod == 0 || mError > kErrorThreshold;
}
void DispSync::endResync() {
}
status_t DispSync::addEventListener(nsecs_t phase,
const sp<Callback>& callback) {
Mutex::Autolock lock(mMutex);
return mThread->addEventListener(phase, callback);
}
void DispSync::setRefreshSkipCount(int count) {
Mutex::Autolock lock(mMutex);
ALOGD("setRefreshSkipCount(%d)", count);
mRefreshSkipCount = count;
updateModelLocked();
}
status_t DispSync::removeEventListener(const sp<Callback>& callback) {
Mutex::Autolock lock(mMutex);
return mThread->removeEventListener(callback);
}
void DispSync::setPeriod(nsecs_t period) {
Mutex::Autolock lock(mMutex);
mPeriod = period;
mPhase = 0;
mThread->updateModel(mPeriod, mPhase);
}
nsecs_t DispSync::getPeriod() {
// lock mutex as mPeriod changes multiple times in updateModelLocked
Mutex::Autolock lock(mMutex);
return mPeriod;
}
void DispSync::updateModelLocked() {
if (mNumResyncSamples >= MIN_RESYNC_SAMPLES_FOR_UPDATE) {
nsecs_t durationSum = 0;
for (size_t i = 1; i < mNumResyncSamples; i++) {
size_t idx = (mFirstResyncSample + i) % MAX_RESYNC_SAMPLES;
size_t prev = (idx + MAX_RESYNC_SAMPLES - 1) % MAX_RESYNC_SAMPLES;
durationSum += mResyncSamples[idx] - mResyncSamples[prev];
}
mPeriod = durationSum / (mNumResyncSamples - 1);
double sampleAvgX = 0;
double sampleAvgY = 0;
double scale = 2.0 * M_PI / double(mPeriod);
for (size_t i = 0; i < mNumResyncSamples; i++) {
size_t idx = (mFirstResyncSample + i) % MAX_RESYNC_SAMPLES;
nsecs_t sample = mResyncSamples[idx];
double samplePhase = double(sample % mPeriod) * scale;
sampleAvgX += cos(samplePhase);
sampleAvgY += sin(samplePhase);
}
sampleAvgX /= double(mNumResyncSamples);
sampleAvgY /= double(mNumResyncSamples);
mPhase = nsecs_t(atan2(sampleAvgY, sampleAvgX) / scale);
if (mPhase < 0) {
mPhase += mPeriod;
}
if (kTraceDetailedInfo) {
ATRACE_INT64("DispSync:Period", mPeriod);
ATRACE_INT64("DispSync:Phase", mPhase);
}
// Artificially inflate the period if requested.
mPeriod += mPeriod * mRefreshSkipCount;
mThread->updateModel(mPeriod, mPhase);
}
}
void DispSync::updateErrorLocked() {
if (mPeriod == 0) {
return;
}
// Need to compare present fences against the un-adjusted refresh period,
// since they might arrive between two events.
nsecs_t period = mPeriod / (1 + mRefreshSkipCount);
int numErrSamples = 0;
nsecs_t sqErrSum = 0;
for (size_t i = 0; i < NUM_PRESENT_SAMPLES; i++) {
nsecs_t sample = mPresentTimes[i];
if (sample > mPhase) {
nsecs_t sampleErr = (sample - mPhase) % period;
if (sampleErr > period / 2) {
sampleErr -= period;
}
sqErrSum += sampleErr * sampleErr;
numErrSamples++;
}
}
if (numErrSamples > 0) {
mError = sqErrSum / numErrSamples;
} else {
mError = 0;
}
if (kTraceDetailedInfo) {
ATRACE_INT64("DispSync:Error", mError);
}
}
void DispSync::resetErrorLocked() {
mPresentSampleOffset = 0;
mError = 0;
for (size_t i = 0; i < NUM_PRESENT_SAMPLES; i++) {
mPresentFences[i].clear();
mPresentTimes[i] = 0;
}
}
nsecs_t DispSync::computeNextRefresh(int periodOffset) const {
Mutex::Autolock lock(mMutex);
nsecs_t now = systemTime(SYSTEM_TIME_MONOTONIC);
return (((now - mPhase) / mPeriod) + periodOffset + 1) * mPeriod + mPhase;
}
void DispSync::dump(String8& result) const {
Mutex::Autolock lock(mMutex);
result.appendFormat("present fences are %s\n",
kIgnorePresentFences ? "ignored" : "used");
result.appendFormat("mPeriod: %" PRId64 " ns (%.3f fps; skipCount=%d)\n",
mPeriod, 1000000000.0 / mPeriod, mRefreshSkipCount);
result.appendFormat("mPhase: %" PRId64 " ns\n", mPhase);
result.appendFormat("mError: %" PRId64 " ns (sqrt=%.1f)\n",
mError, sqrt(mError));
result.appendFormat("mNumResyncSamplesSincePresent: %d (limit %d)\n",
mNumResyncSamplesSincePresent, MAX_RESYNC_SAMPLES_WITHOUT_PRESENT);
result.appendFormat("mNumResyncSamples: %zd (max %d)\n",
mNumResyncSamples, MAX_RESYNC_SAMPLES);
result.appendFormat("mResyncSamples:\n");
nsecs_t previous = -1;
for (size_t i = 0; i < mNumResyncSamples; i++) {
size_t idx = (mFirstResyncSample + i) % MAX_RESYNC_SAMPLES;
nsecs_t sampleTime = mResyncSamples[idx];
if (i == 0) {
result.appendFormat(" %" PRId64 "\n", sampleTime);
} else {
result.appendFormat(" %" PRId64 " (+%" PRId64 ")\n",
sampleTime, sampleTime - previous);
}
previous = sampleTime;
}
result.appendFormat("mPresentFences / mPresentTimes [%d]:\n",
NUM_PRESENT_SAMPLES);
nsecs_t now = systemTime(SYSTEM_TIME_MONOTONIC);
previous = 0;
for (size_t i = 0; i < NUM_PRESENT_SAMPLES; i++) {
size_t idx = (i + mPresentSampleOffset) % NUM_PRESENT_SAMPLES;
bool signaled = mPresentFences[idx] == NULL;
nsecs_t presentTime = mPresentTimes[idx];
if (!signaled) {
result.appendFormat(" [unsignaled fence]\n");
} else if (presentTime == 0) {
result.appendFormat(" 0\n");
} else if (previous == 0) {
result.appendFormat(" %" PRId64 " (%.3f ms ago)\n", presentTime,
(now - presentTime) / 1000000.0);
} else {
result.appendFormat(" %" PRId64 " (+%" PRId64 " / %.3f) (%.3f ms ago)\n",
presentTime, presentTime - previous,
(presentTime - previous) / (double) mPeriod,
(now - presentTime) / 1000000.0);
}
previous = presentTime;
}
result.appendFormat("current monotonic time: %" PRId64 "\n", now);
}
} // namespace android