services/surfaceflinger/Scheduler/VSyncPredictor.cpp - LeafOS-Project/android_frameworks_native - Gitiles

 /*
  * Copyright 2019 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.
  */

 // TODO(b/129481165): remove the #pragma below and fix conversion issues
 #pragma clang diagnostic push
 #pragma clang diagnostic ignored "-Wextra"

 #undef LOG_TAG
 #define LOG_TAG "VSyncPredictor"

 #define ATRACE_TAG ATRACE_TAG_GRAPHICS

 #include <algorithm>
 #include <chrono>
 #include <sstream>

 #include <android-base/logging.h>
 #include <android-base/stringprintf.h>
 #include <common/FlagManager.h>
 #include <cutils/compiler.h>
 #include <cutils/properties.h>
 #include <ftl/concat.h>
 #include <gui/TraceUtils.h>
 #include <utils/Log.h>

 #include "RefreshRateSelector.h"
 #include "VSyncPredictor.h"

 namespace android::scheduler {

 using base::StringAppendF;

 static auto constexpr kMaxPercent = 100u;

 VSyncPredictor::~VSyncPredictor() = default;

 VSyncPredictor::VSyncPredictor(ftl::NonNull<DisplayModePtr> modePtr, size_t historySize,
                                size_t minimumSamplesForPrediction, uint32_t outlierTolerancePercent)
       : mId(modePtr->getPhysicalDisplayId()),
         mTraceOn(property_get_bool("debug.sf.vsp_trace", false)),
         kHistorySize(historySize),
         kMinimumSamplesForPrediction(minimumSamplesForPrediction),
         kOutlierTolerancePercent(std::min(outlierTolerancePercent, kMaxPercent)),
         mDisplayModePtr(modePtr) {
     resetModel();
 }

 inline void VSyncPredictor::traceInt64If(const char* name, int64_t value) const {
     if (CC_UNLIKELY(mTraceOn)) {
         traceInt64(name, value);
     }
 }

 inline void VSyncPredictor::traceInt64(const char* name, int64_t value) const {
     ATRACE_INT64(ftl::Concat(ftl::truncated<14>(name), " ", mId.value).c_str(), value);
 }

 inline size_t VSyncPredictor::next(size_t i) const {
     return (i + 1) % mTimestamps.size();
 }

 nsecs_t VSyncPredictor::idealPeriod() const {
     return mDisplayModePtr->getVsyncRate().getPeriodNsecs();
 }

 bool VSyncPredictor::validate(nsecs_t timestamp) const {
     if (mLastTimestampIndex < 0 || mTimestamps.empty()) {
         return true;
     }

     const auto aValidTimestamp = mTimestamps[mLastTimestampIndex];
     const auto percent =
             (timestamp - aValidTimestamp) % idealPeriod() * kMaxPercent / idealPeriod();
     if (percent >= kOutlierTolerancePercent &&
         percent <= (kMaxPercent - kOutlierTolerancePercent)) {
         ATRACE_FORMAT_INSTANT("timestamp is not aligned with model");
         return false;
     }

     const auto iter = std::min_element(mTimestamps.begin(), mTimestamps.end(),
                                        [timestamp](nsecs_t a, nsecs_t b) {
                                            return std::abs(timestamp - a) < std::abs(timestamp - b);
                                        });
     const auto distancePercent = std::abs(*iter - timestamp) * kMaxPercent / idealPeriod();
     if (distancePercent < kOutlierTolerancePercent) {
         // duplicate timestamp
         ATRACE_FORMAT_INSTANT("duplicate timestamp");
         return false;
     }
     return true;
 }

 nsecs_t VSyncPredictor::currentPeriod() const {
     std::lock_guard lock(mMutex);
     return mRateMap.find(idealPeriod())->second.slope;
 }

 Period VSyncPredictor::minFramePeriod() const {
     if (!FlagManager::getInstance().vrr_config()) {
         return Period::fromNs(currentPeriod());
     }

     std::lock_guard lock(mMutex);
     return minFramePeriodLocked();
 }

 Period VSyncPredictor::minFramePeriodLocked() const {
     const auto idealPeakRefreshPeriod = mDisplayModePtr->getPeakFps().getPeriodNsecs();
     const auto numPeriods = static_cast<int>(std::round(static_cast<float>(idealPeakRefreshPeriod) /
                                                         static_cast<float>(idealPeriod())));
     const auto slope = mRateMap.find(idealPeriod())->second.slope;
     return Period::fromNs(slope * numPeriods);
 }

 bool VSyncPredictor::addVsyncTimestamp(nsecs_t timestamp) {
     ATRACE_CALL();

     std::lock_guard lock(mMutex);

     if (!validate(timestamp)) {
         // VSR could elect to ignore the incongruent timestamp or resetModel(). If ts is ignored,
         // don't insert this ts into mTimestamps ringbuffer. If we are still
         // in the learning phase we should just clear all timestamps and start
         // over.
         if (mTimestamps.size() < kMinimumSamplesForPrediction) {
             // Add the timestamp to mTimestamps before clearing it so we could
             // update mKnownTimestamp based on the new timestamp.
             mTimestamps.push_back(timestamp);
             clearTimestamps();
         } else if (!mTimestamps.empty()) {
             mKnownTimestamp =
                     std::max(timestamp, *std::max_element(mTimestamps.begin(), mTimestamps.end()));
         } else {
             mKnownTimestamp = timestamp;
         }
         ATRACE_FORMAT_INSTANT("timestamp rejected. mKnownTimestamp was %.2fms ago",
             (systemTime() - *mKnownTimestamp) / 1e6f);
         return false;
     }

     if (mTimestamps.size() != kHistorySize) {
         mTimestamps.push_back(timestamp);
         mLastTimestampIndex = next(mLastTimestampIndex);
     } else {
         mLastTimestampIndex = next(mLastTimestampIndex);
         mTimestamps[mLastTimestampIndex] = timestamp;
     }

     traceInt64If("VSP-ts", timestamp);

     const size_t numSamples = mTimestamps.size();
     if (numSamples < kMinimumSamplesForPrediction) {
         mRateMap[idealPeriod()] = {idealPeriod(), 0};
         return true;
     }

     // This is a 'simple linear regression' calculation of Y over X, with Y being the
     // vsync timestamps, and X being the ordinal of vsync count.
     // The calculated slope is the vsync period.
     // Formula for reference:
     // Sigma_i: means sum over all timestamps.
     // mean(variable): statistical mean of variable.
     // X: snapped ordinal of the timestamp
     // Y: vsync timestamp
     //
     //         Sigma_i( (X_i - mean(X)) * (Y_i - mean(Y) )
     // slope = -------------------------------------------
     //         Sigma_i ( X_i - mean(X) ) ^ 2
     //
     // intercept = mean(Y) - slope * mean(X)
     //
     std::vector<nsecs_t> vsyncTS(numSamples);
     std::vector<nsecs_t> ordinals(numSamples);

     // Normalizing to the oldest timestamp cuts down on error in calculating the intercept.
     const auto oldestTS = *std::min_element(mTimestamps.begin(), mTimestamps.end());
     auto it = mRateMap.find(idealPeriod());
     auto const currentPeriod = it->second.slope;

     // The mean of the ordinals must be precise for the intercept calculation, so scale them up for
     // fixed-point arithmetic.
     constexpr int64_t kScalingFactor = 1000;

     nsecs_t meanTS = 0;
     nsecs_t meanOrdinal = 0;

     for (size_t i = 0; i < numSamples; i++) {
         const auto timestamp = mTimestamps[i] - oldestTS;
         vsyncTS[i] = timestamp;
         meanTS += timestamp;

         const auto ordinal = currentPeriod == 0
                 ? 0
                 : (vsyncTS[i] + currentPeriod / 2) / currentPeriod * kScalingFactor;
         ordinals[i] = ordinal;
         meanOrdinal += ordinal;
     }

     meanTS /= numSamples;
     meanOrdinal /= numSamples;

     for (size_t i = 0; i < numSamples; i++) {
         vsyncTS[i] -= meanTS;
         ordinals[i] -= meanOrdinal;
     }

     nsecs_t top = 0;
     nsecs_t bottom = 0;
     for (size_t i = 0; i < numSamples; i++) {
         top += vsyncTS[i] * ordinals[i];
         bottom += ordinals[i] * ordinals[i];
     }

     if (CC_UNLIKELY(bottom == 0)) {
         it->second = {idealPeriod(), 0};
         clearTimestamps();
         return false;
     }

     nsecs_t const anticipatedPeriod = top * kScalingFactor / bottom;
     nsecs_t const intercept = meanTS - (anticipatedPeriod * meanOrdinal / kScalingFactor);

     auto const percent = std::abs(anticipatedPeriod - idealPeriod()) * kMaxPercent / idealPeriod();
     if (percent >= kOutlierTolerancePercent) {
         it->second = {idealPeriod(), 0};
         clearTimestamps();
         return false;
     }

     traceInt64If("VSP-period", anticipatedPeriod);
     traceInt64If("VSP-intercept", intercept);

     it->second = {anticipatedPeriod, intercept};

     ALOGV("model update ts %" PRIu64 ": %" PRId64 " slope: %" PRId64 " intercept: %" PRId64,
           mId.value, timestamp, anticipatedPeriod, intercept);
     return true;
 }

 auto VSyncPredictor::getVsyncSequenceLocked(nsecs_t timestamp) const -> VsyncSequence {
     const auto vsync = snapToVsync(timestamp);
     if (!mLastVsyncSequence) return {vsync, 0};

     const auto [slope, _] = getVSyncPredictionModelLocked();
     const auto [lastVsyncTime, lastVsyncSequence] = *mLastVsyncSequence;
     const auto vsyncSequence = lastVsyncSequence +
             static_cast<int64_t>(std::round((vsync - lastVsyncTime) / static_cast<float>(slope)));
     return {vsync, vsyncSequence};
 }

 nsecs_t VSyncPredictor::snapToVsync(nsecs_t timePoint) const {
     auto const [slope, intercept] = getVSyncPredictionModelLocked();

     if (mTimestamps.empty()) {
         traceInt64("VSP-mode", 1);
         auto const knownTimestamp = mKnownTimestamp ? *mKnownTimestamp : timePoint;
         auto const numPeriodsOut = ((timePoint - knownTimestamp) / idealPeriod()) + 1;
         return knownTimestamp + numPeriodsOut * idealPeriod();
     }

     auto const oldest = *std::min_element(mTimestamps.begin(), mTimestamps.end());

     // See b/145667109, the ordinal calculation must take into account the intercept.
     auto const zeroPoint = oldest + intercept;
     auto const ordinalRequest = (timePoint - zeroPoint + slope) / slope;
     auto const prediction = (ordinalRequest * slope) + intercept + oldest;

     traceInt64("VSP-mode", 0);
     traceInt64If("VSP-timePoint", timePoint);
     traceInt64If("VSP-prediction", prediction);

     auto const printer = [&, slope = slope, intercept = intercept] {
         std::stringstream str;
         str << "prediction made from: " << timePoint << "prediction: " << prediction << " (+"
             << prediction - timePoint << ") slope: " << slope << " intercept: " << intercept
             << "oldestTS: " << oldest << " ordinal: " << ordinalRequest;
         return str.str();
     };

     ALOGV("%s", printer().c_str());
     LOG_ALWAYS_FATAL_IF(prediction < timePoint, "VSyncPredictor: model miscalculation: %s",
                         printer().c_str());

     return prediction;
 }

 nsecs_t VSyncPredictor::nextAnticipatedVSyncTimeFrom(nsecs_t timePoint,
                                                      std::optional<nsecs_t> lastVsyncOpt) const {
     ATRACE_CALL();
     std::lock_guard lock(mMutex);
     const auto currentPeriod = mRateMap.find(idealPeriod())->second.slope;
     const auto threshold = currentPeriod / 2;
     const auto minFramePeriod = minFramePeriodLocked().ns();
     const auto lastFrameMissed =
             lastVsyncOpt && std::abs(*lastVsyncOpt - mLastMissedVsync.ns()) < threshold;
     const nsecs_t baseTime =
             FlagManager::getInstance().vrr_config() && !lastFrameMissed && lastVsyncOpt
             ? std::max(timePoint, *lastVsyncOpt + minFramePeriod - threshold)
             : timePoint;
     return snapToVsyncAlignedWithRenderRate(baseTime);
 }

 nsecs_t VSyncPredictor::snapToVsyncAlignedWithRenderRate(nsecs_t timePoint) const {
     // update the mLastVsyncSequence for reference point
     mLastVsyncSequence = getVsyncSequenceLocked(timePoint);

     const auto renderRatePhase = [&]() REQUIRES(mMutex) -> int {
         if (!mRenderRateOpt) return 0;
         const auto divisor =
                 RefreshRateSelector::getFrameRateDivisor(Fps::fromPeriodNsecs(idealPeriod()),
                                                          *mRenderRateOpt);
         if (divisor <= 1) return 0;

         int mod = mLastVsyncSequence->seq % divisor;
         if (mod == 0) return 0;

         // This is actually a bug fix, but guarded with vrr_config since we found it with this
         // config
         if (FlagManager::getInstance().vrr_config()) {
             if (mod < 0) mod += divisor;
         }

         return divisor - mod;
     }();

     if (renderRatePhase == 0) {
         return mLastVsyncSequence->vsyncTime;
     }

     auto const [slope, intercept] = getVSyncPredictionModelLocked();
     const auto approximateNextVsync = mLastVsyncSequence->vsyncTime + slope * renderRatePhase;
     return snapToVsync(approximateNextVsync - slope / 2);
 }

 /*
  * Returns whether a given vsync timestamp is in phase with a frame rate.
  * If the frame rate is not a divisor of the refresh rate, it is always considered in phase.
  * For example, if the vsync timestamps are (16.6,33.3,50.0,66.6):
  * isVSyncInPhase(16.6, 30) = true
  * isVSyncInPhase(33.3, 30) = false
  * isVSyncInPhase(50.0, 30) = true
  */
 bool VSyncPredictor::isVSyncInPhase(nsecs_t timePoint, Fps frameRate) const {
     std::lock_guard lock(mMutex);
     const auto divisor =
             RefreshRateSelector::getFrameRateDivisor(Fps::fromPeriodNsecs(idealPeriod()),
                                                      frameRate);
     return isVSyncInPhaseLocked(timePoint, static_cast<unsigned>(divisor));
 }

 bool VSyncPredictor::isVSyncInPhaseLocked(nsecs_t timePoint, unsigned divisor) const {
     const TimePoint now = TimePoint::now();
     const auto getTimePointIn = [](TimePoint now, nsecs_t timePoint) -> float {
         return ticks<std::milli, float>(TimePoint::fromNs(timePoint) - now);
     };
     ATRACE_FORMAT("%s timePoint in: %.2f divisor: %zu", __func__, getTimePointIn(now, timePoint),
                   divisor);

     if (divisor <= 1 || timePoint == 0) {
         return true;
     }

     const nsecs_t period = mRateMap[idealPeriod()].slope;
     const nsecs_t justBeforeTimePoint = timePoint - period / 2;
     const auto vsyncSequence = getVsyncSequenceLocked(justBeforeTimePoint);
     ATRACE_FORMAT_INSTANT("vsync in: %.2f sequence: %" PRId64,
                           getTimePointIn(now, vsyncSequence.vsyncTime), vsyncSequence.seq);
     return vsyncSequence.seq % divisor == 0;
 }

 void VSyncPredictor::setRenderRate(Fps renderRate) {
     ATRACE_FORMAT("%s %s", __func__, to_string(renderRate).c_str());
     ALOGV("%s %s: RenderRate %s ", __func__, to_string(mId).c_str(), to_string(renderRate).c_str());
     std::lock_guard lock(mMutex);
     mRenderRateOpt = renderRate;
 }

 void VSyncPredictor::setDisplayModePtr(ftl::NonNull<DisplayModePtr> modePtr) {
     LOG_ALWAYS_FATAL_IF(mId != modePtr->getPhysicalDisplayId(),
                         "mode does not belong to the display");
     ATRACE_FORMAT("%s %s", __func__, to_string(*modePtr).c_str());
     const auto timeout = modePtr->getVrrConfig()
             ? modePtr->getVrrConfig()->notifyExpectedPresentConfig
             : std::nullopt;
     ALOGV("%s %s: DisplayMode %s notifyExpectedPresentTimeout %s", __func__, to_string(mId).c_str(),
           to_string(*modePtr).c_str(),
           timeout ? std::to_string(timeout->timeoutNs).c_str() : "N/A");
     std::lock_guard lock(mMutex);

     mDisplayModePtr = modePtr;
     traceInt64("VSP-setPeriod", modePtr->getVsyncRate().getPeriodNsecs());

     static constexpr size_t kSizeLimit = 30;
     if (CC_UNLIKELY(mRateMap.size() == kSizeLimit)) {
         mRateMap.erase(mRateMap.begin());
     }

     if (mRateMap.find(idealPeriod()) == mRateMap.end()) {
         mRateMap[idealPeriod()] = {idealPeriod(), 0};
     }

     clearTimestamps();
 }

 void VSyncPredictor::ensureMinFrameDurationIsKept(TimePoint expectedPresentTime,
                                                   TimePoint lastConfirmedPresentTime) {
     const auto currentPeriod = mRateMap.find(idealPeriod())->second.slope;
     const auto threshold = currentPeriod / 2;
     const auto minFramePeriod = minFramePeriodLocked().ns();

     auto prev = lastConfirmedPresentTime.ns();
     for (auto& current : mPastExpectedPresentTimes) {
         if (CC_UNLIKELY(mTraceOn)) {
             ATRACE_FORMAT_INSTANT("current %.2f past last signaled fence",
                                   static_cast<float>(current.ns() - lastConfirmedPresentTime.ns()) /
                                           1e6f);
         }

         const auto minPeriodViolation = current.ns() - prev + threshold < minFramePeriod;
         if (minPeriodViolation) {
             ATRACE_NAME("minPeriodViolation");
             current = TimePoint::fromNs(prev + minFramePeriod);
             prev = current.ns();
         } else {
             break;
         }
     }

     if (!mPastExpectedPresentTimes.empty()) {
         const auto phase = Duration(mPastExpectedPresentTimes.back() - expectedPresentTime);
         if (phase > 0ns) {
             if (mLastVsyncSequence) {
                 mLastVsyncSequence->vsyncTime += phase.ns();
             }
             mPastExpectedPresentTimes.clear();
         }
     }
 }

 void VSyncPredictor::onFrameBegin(TimePoint expectedPresentTime,
                                   TimePoint lastConfirmedPresentTime) {
     ATRACE_CALL();
     std::lock_guard lock(mMutex);

     if (!mDisplayModePtr->getVrrConfig()) return;

     if (CC_UNLIKELY(mTraceOn)) {
         ATRACE_FORMAT_INSTANT("vsync is %.2f past last signaled fence",
                               static_cast<float>(expectedPresentTime.ns() -
                                                  lastConfirmedPresentTime.ns()) /
                                       1e6f);
     }
     const auto currentPeriod = mRateMap.find(idealPeriod())->second.slope;
     const auto threshold = currentPeriod / 2;
     mPastExpectedPresentTimes.push_back(expectedPresentTime);

     while (!mPastExpectedPresentTimes.empty()) {
         const auto front = mPastExpectedPresentTimes.front().ns();
         const bool frontIsBeforeConfirmed = front < lastConfirmedPresentTime.ns() + threshold;
         if (frontIsBeforeConfirmed) {
             if (CC_UNLIKELY(mTraceOn)) {
                 ATRACE_FORMAT_INSTANT("Discarding old vsync - %.2f before last signaled fence",
                                       static_cast<float>(lastConfirmedPresentTime.ns() - front) /
                                               1e6f);
             }
             mPastExpectedPresentTimes.pop_front();
         } else {
             break;
         }
     }

     ensureMinFrameDurationIsKept(expectedPresentTime, lastConfirmedPresentTime);
 }

 void VSyncPredictor::onFrameMissed(TimePoint expectedPresentTime) {
     ATRACE_CALL();

     std::lock_guard lock(mMutex);
     if (!mDisplayModePtr->getVrrConfig()) return;

     // We don't know when the frame is going to be presented, so we assume it missed one vsync
     const auto currentPeriod = mRateMap.find(idealPeriod())->second.slope;
     const auto lastConfirmedPresentTime =
             TimePoint::fromNs(expectedPresentTime.ns() + currentPeriod);

     ensureMinFrameDurationIsKept(expectedPresentTime, lastConfirmedPresentTime);
     mLastMissedVsync = expectedPresentTime;
 }

 VSyncPredictor::Model VSyncPredictor::getVSyncPredictionModel() const {
     std::lock_guard lock(mMutex);
     const auto model = VSyncPredictor::getVSyncPredictionModelLocked();
     return {model.slope, model.intercept};
 }

 VSyncPredictor::Model VSyncPredictor::getVSyncPredictionModelLocked() const {
     return mRateMap.find(idealPeriod())->second;
 }

 void VSyncPredictor::clearTimestamps() {
     ATRACE_CALL();

     if (!mTimestamps.empty()) {
         auto const maxRb = *std::max_element(mTimestamps.begin(), mTimestamps.end());
         if (mKnownTimestamp) {
             mKnownTimestamp = std::max(*mKnownTimestamp, maxRb);
         } else {
             mKnownTimestamp = maxRb;
         }

         mTimestamps.clear();
         mLastTimestampIndex = 0;
     }
 }

 bool VSyncPredictor::needsMoreSamples() const {
     std::lock_guard lock(mMutex);
     return mTimestamps.size() < kMinimumSamplesForPrediction;
 }

 void VSyncPredictor::resetModel() {
     std::lock_guard lock(mMutex);
     mRateMap[idealPeriod()] = {idealPeriod(), 0};
     clearTimestamps();
 }

 void VSyncPredictor::dump(std::string& result) const {
     std::lock_guard lock(mMutex);
     StringAppendF(&result, "\tmDisplayModePtr=%s\n", to_string(*mDisplayModePtr).c_str());
     StringAppendF(&result, "\tRefresh Rate Map:\n");
     for (const auto& [period, periodInterceptTuple] : mRateMap) {
         StringAppendF(&result,
                       "\t\tFor ideal period %.2fms: period = %.2fms, intercept = %" PRId64 "\n",
                       period / 1e6f, periodInterceptTuple.slope / 1e6f,
                       periodInterceptTuple.intercept);
     }
 }

 } // namespace android::scheduler

 // TODO(b/129481165): remove the #pragma below and fix conversion issues
 #pragma clang diagnostic pop // ignored "-Wextra"
	/*
	* Copyright 2019 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.
	*/

	// TODO(b/129481165): remove the #pragma below and fix conversion issues
	#pragma clang diagnostic push
	#pragma clang diagnostic ignored "-Wextra"

	#undef LOG_TAG
	#define LOG_TAG "VSyncPredictor"

	#define ATRACE_TAG ATRACE_TAG_GRAPHICS

	#include <algorithm>
	#include <chrono>
	#include <sstream>

	#include <android-base/logging.h>
	#include <android-base/stringprintf.h>
	#include <common/FlagManager.h>
	#include <cutils/compiler.h>
	#include <cutils/properties.h>
	#include <ftl/concat.h>
	#include <gui/TraceUtils.h>
	#include <utils/Log.h>

	#include "RefreshRateSelector.h"
	#include "VSyncPredictor.h"

	namespace android::scheduler {

	using base::StringAppendF;

	static auto constexpr kMaxPercent = 100u;

	VSyncPredictor::~VSyncPredictor() = default;

	VSyncPredictor::VSyncPredictor(ftl::NonNull<DisplayModePtr> modePtr, size_t historySize,
	size_t minimumSamplesForPrediction, uint32_t outlierTolerancePercent)
	: mId(modePtr->getPhysicalDisplayId()),
	mTraceOn(property_get_bool("debug.sf.vsp_trace", false)),
	kHistorySize(historySize),
	kMinimumSamplesForPrediction(minimumSamplesForPrediction),
	kOutlierTolerancePercent(std::min(outlierTolerancePercent, kMaxPercent)),
	mDisplayModePtr(modePtr) {
	resetModel();
	}

	inline void VSyncPredictor::traceInt64If(const char* name, int64_t value) const {
	if (CC_UNLIKELY(mTraceOn)) {
	traceInt64(name, value);
	}
	}

	inline void VSyncPredictor::traceInt64(const char* name, int64_t value) const {
	ATRACE_INT64(ftl::Concat(ftl::truncated<14>(name), " ", mId.value).c_str(), value);
	}

	inline size_t VSyncPredictor::next(size_t i) const {
	return (i + 1) % mTimestamps.size();
	}

	nsecs_t VSyncPredictor::idealPeriod() const {
	return mDisplayModePtr->getVsyncRate().getPeriodNsecs();
	}

	bool VSyncPredictor::validate(nsecs_t timestamp) const {
	if (mLastTimestampIndex < 0 \|\| mTimestamps.empty()) {
	return true;
	}

	const auto aValidTimestamp = mTimestamps[mLastTimestampIndex];
	const auto percent =
	(timestamp - aValidTimestamp) % idealPeriod() * kMaxPercent / idealPeriod();
	if (percent >= kOutlierTolerancePercent &&
	percent <= (kMaxPercent - kOutlierTolerancePercent)) {
	ATRACE_FORMAT_INSTANT("timestamp is not aligned with model");
	return false;
	}

	const auto iter = std::min_element(mTimestamps.begin(), mTimestamps.end(),
	[timestamp](nsecs_t a, nsecs_t b) {
	return std::abs(timestamp - a) < std::abs(timestamp - b);
	});
	const auto distancePercent = std::abs(iter - timestamp) kMaxPercent / idealPeriod();
	if (distancePercent < kOutlierTolerancePercent) {
	// duplicate timestamp
	ATRACE_FORMAT_INSTANT("duplicate timestamp");
	return false;
	}
	return true;
	}

	nsecs_t VSyncPredictor::currentPeriod() const {
	std::lock_guard lock(mMutex);
	return mRateMap.find(idealPeriod())->second.slope;
	}

	Period VSyncPredictor::minFramePeriod() const {
	if (!FlagManager::getInstance().vrr_config()) {
	return Period::fromNs(currentPeriod());
	}

	std::lock_guard lock(mMutex);
	return minFramePeriodLocked();
	}

	Period VSyncPredictor::minFramePeriodLocked() const {
	const auto idealPeakRefreshPeriod = mDisplayModePtr->getPeakFps().getPeriodNsecs();
	const auto numPeriods = static_cast<int>(std::round(static_cast<float>(idealPeakRefreshPeriod) /
	static_cast<float>(idealPeriod())));
	const auto slope = mRateMap.find(idealPeriod())->second.slope;
	return Period::fromNs(slope * numPeriods);
	}

	bool VSyncPredictor::addVsyncTimestamp(nsecs_t timestamp) {
	ATRACE_CALL();

	std::lock_guard lock(mMutex);

	if (!validate(timestamp)) {
	// VSR could elect to ignore the incongruent timestamp or resetModel(). If ts is ignored,
	// don't insert this ts into mTimestamps ringbuffer. If we are still
	// in the learning phase we should just clear all timestamps and start
	// over.
	if (mTimestamps.size() < kMinimumSamplesForPrediction) {
	// Add the timestamp to mTimestamps before clearing it so we could
	// update mKnownTimestamp based on the new timestamp.
	mTimestamps.push_back(timestamp);
	clearTimestamps();
	} else if (!mTimestamps.empty()) {
	mKnownTimestamp =
	std::max(timestamp, *std::max_element(mTimestamps.begin(), mTimestamps.end()));
	} else {
	mKnownTimestamp = timestamp;
	}
	ATRACE_FORMAT_INSTANT("timestamp rejected. mKnownTimestamp was %.2fms ago",
	(systemTime() - *mKnownTimestamp) / 1e6f);
	return false;
	}

	if (mTimestamps.size() != kHistorySize) {
	mTimestamps.push_back(timestamp);
	mLastTimestampIndex = next(mLastTimestampIndex);
	} else {
	mLastTimestampIndex = next(mLastTimestampIndex);
	mTimestamps[mLastTimestampIndex] = timestamp;
	}

	traceInt64If("VSP-ts", timestamp);

	const size_t numSamples = mTimestamps.size();
	if (numSamples < kMinimumSamplesForPrediction) {
	mRateMap[idealPeriod()] = {idealPeriod(), 0};
	return true;
	}

	// This is a 'simple linear regression' calculation of Y over X, with Y being the
	// vsync timestamps, and X being the ordinal of vsync count.
	// The calculated slope is the vsync period.
	// Formula for reference:
	// Sigma_i: means sum over all timestamps.
	// mean(variable): statistical mean of variable.
	// X: snapped ordinal of the timestamp
	// Y: vsync timestamp
	//
	// Sigma_i( (X_i - mean(X)) * (Y_i - mean(Y) )
	// slope = -------------------------------------------
	// Sigma_i ( X_i - mean(X) ) ^ 2
	//
	// intercept = mean(Y) - slope * mean(X)
	//
	std::vector<nsecs_t> vsyncTS(numSamples);
	std::vector<nsecs_t> ordinals(numSamples);

	// Normalizing to the oldest timestamp cuts down on error in calculating the intercept.
	const auto oldestTS = *std::min_element(mTimestamps.begin(), mTimestamps.end());
	auto it = mRateMap.find(idealPeriod());
	auto const currentPeriod = it->second.slope;

	// The mean of the ordinals must be precise for the intercept calculation, so scale them up for
	// fixed-point arithmetic.
	constexpr int64_t kScalingFactor = 1000;

	nsecs_t meanTS = 0;
	nsecs_t meanOrdinal = 0;

	for (size_t i = 0; i < numSamples; i++) {
	const auto timestamp = mTimestamps[i] - oldestTS;
	vsyncTS[i] = timestamp;
	meanTS += timestamp;

	const auto ordinal = currentPeriod == 0
	? 0
	: (vsyncTS[i] + currentPeriod / 2) / currentPeriod * kScalingFactor;
	ordinals[i] = ordinal;
	meanOrdinal += ordinal;
	}

	meanTS /= numSamples;
	meanOrdinal /= numSamples;

	for (size_t i = 0; i < numSamples; i++) {
	vsyncTS[i] -= meanTS;
	ordinals[i] -= meanOrdinal;
	}

	nsecs_t top = 0;
	nsecs_t bottom = 0;
	for (size_t i = 0; i < numSamples; i++) {
	top += vsyncTS[i] * ordinals[i];
	bottom += ordinals[i] * ordinals[i];
	}

	if (CC_UNLIKELY(bottom == 0)) {
	it->second = {idealPeriod(), 0};
	clearTimestamps();
	return false;
	}

	nsecs_t const anticipatedPeriod = top * kScalingFactor / bottom;
	nsecs_t const intercept = meanTS - (anticipatedPeriod * meanOrdinal / kScalingFactor);

	auto const percent = std::abs(anticipatedPeriod - idealPeriod()) * kMaxPercent / idealPeriod();
	if (percent >= kOutlierTolerancePercent) {
	it->second = {idealPeriod(), 0};
	clearTimestamps();
	return false;
	}

	traceInt64If("VSP-period", anticipatedPeriod);
	traceInt64If("VSP-intercept", intercept);

	it->second = {anticipatedPeriod, intercept};

	ALOGV("model update ts %" PRIu64 ": %" PRId64 " slope: %" PRId64 " intercept: %" PRId64,
	mId.value, timestamp, anticipatedPeriod, intercept);
	return true;
	}

	auto VSyncPredictor::getVsyncSequenceLocked(nsecs_t timestamp) const -> VsyncSequence {
	const auto vsync = snapToVsync(timestamp);
	if (!mLastVsyncSequence) return {vsync, 0};

	const auto [slope, _] = getVSyncPredictionModelLocked();
	const auto [lastVsyncTime, lastVsyncSequence] = *mLastVsyncSequence;
	const auto vsyncSequence = lastVsyncSequence +
	static_cast<int64_t>(std::round((vsync - lastVsyncTime) / static_cast<float>(slope)));
	return {vsync, vsyncSequence};
	}

	nsecs_t VSyncPredictor::snapToVsync(nsecs_t timePoint) const {
	auto const [slope, intercept] = getVSyncPredictionModelLocked();

	if (mTimestamps.empty()) {
	traceInt64("VSP-mode", 1);
	auto const knownTimestamp = mKnownTimestamp ? *mKnownTimestamp : timePoint;
	auto const numPeriodsOut = ((timePoint - knownTimestamp) / idealPeriod()) + 1;
	return knownTimestamp + numPeriodsOut * idealPeriod();
	}

	auto const oldest = *std::min_element(mTimestamps.begin(), mTimestamps.end());

	// See b/145667109, the ordinal calculation must take into account the intercept.
	auto const zeroPoint = oldest + intercept;
	auto const ordinalRequest = (timePoint - zeroPoint + slope) / slope;
	auto const prediction = (ordinalRequest * slope) + intercept + oldest;

	traceInt64("VSP-mode", 0);
	traceInt64If("VSP-timePoint", timePoint);
	traceInt64If("VSP-prediction", prediction);

	auto const printer = [&, slope = slope, intercept = intercept] {
	std::stringstream str;
	str << "prediction made from: " << timePoint << "prediction: " << prediction << " (+"
	<< prediction - timePoint << ") slope: " << slope << " intercept: " << intercept
	<< "oldestTS: " << oldest << " ordinal: " << ordinalRequest;
	return str.str();
	};

	ALOGV("%s", printer().c_str());
	LOG_ALWAYS_FATAL_IF(prediction < timePoint, "VSyncPredictor: model miscalculation: %s",
	printer().c_str());

	return prediction;
	}

	nsecs_t VSyncPredictor::nextAnticipatedVSyncTimeFrom(nsecs_t timePoint,
	std::optional<nsecs_t> lastVsyncOpt) const {
	ATRACE_CALL();
	std::lock_guard lock(mMutex);
	const auto currentPeriod = mRateMap.find(idealPeriod())->second.slope;
	const auto threshold = currentPeriod / 2;
	const auto minFramePeriod = minFramePeriodLocked().ns();
	const auto lastFrameMissed =
	lastVsyncOpt && std::abs(*lastVsyncOpt - mLastMissedVsync.ns()) < threshold;
	const nsecs_t baseTime =
	FlagManager::getInstance().vrr_config() && !lastFrameMissed && lastVsyncOpt
	? std::max(timePoint, *lastVsyncOpt + minFramePeriod - threshold)
	: timePoint;
	return snapToVsyncAlignedWithRenderRate(baseTime);
	}

	nsecs_t VSyncPredictor::snapToVsyncAlignedWithRenderRate(nsecs_t timePoint) const {
	// update the mLastVsyncSequence for reference point
	mLastVsyncSequence = getVsyncSequenceLocked(timePoint);

	const auto renderRatePhase = [&]() REQUIRES(mMutex) -> int {
	if (!mRenderRateOpt) return 0;
	const auto divisor =
	RefreshRateSelector::getFrameRateDivisor(Fps::fromPeriodNsecs(idealPeriod()),
	*mRenderRateOpt);
	if (divisor <= 1) return 0;

	int mod = mLastVsyncSequence->seq % divisor;
	if (mod == 0) return 0;

	// This is actually a bug fix, but guarded with vrr_config since we found it with this
	// config
	if (FlagManager::getInstance().vrr_config()) {
	if (mod < 0) mod += divisor;
	}

	return divisor - mod;
	}();

	if (renderRatePhase == 0) {
	return mLastVsyncSequence->vsyncTime;
	}

	auto const [slope, intercept] = getVSyncPredictionModelLocked();
	const auto approximateNextVsync = mLastVsyncSequence->vsyncTime + slope * renderRatePhase;
	return snapToVsync(approximateNextVsync - slope / 2);
	}

	/*
	* Returns whether a given vsync timestamp is in phase with a frame rate.
	* If the frame rate is not a divisor of the refresh rate, it is always considered in phase.
	* For example, if the vsync timestamps are (16.6,33.3,50.0,66.6):
	* isVSyncInPhase(16.6, 30) = true
	* isVSyncInPhase(33.3, 30) = false
	* isVSyncInPhase(50.0, 30) = true
	*/
	bool VSyncPredictor::isVSyncInPhase(nsecs_t timePoint, Fps frameRate) const {
	std::lock_guard lock(mMutex);
	const auto divisor =
	RefreshRateSelector::getFrameRateDivisor(Fps::fromPeriodNsecs(idealPeriod()),
	frameRate);
	return isVSyncInPhaseLocked(timePoint, static_cast<unsigned>(divisor));
	}

	bool VSyncPredictor::isVSyncInPhaseLocked(nsecs_t timePoint, unsigned divisor) const {
	const TimePoint now = TimePoint::now();
	const auto getTimePointIn = [](TimePoint now, nsecs_t timePoint) -> float {
	return ticks<std::milli, float>(TimePoint::fromNs(timePoint) - now);
	};
	ATRACE_FORMAT("%s timePoint in: %.2f divisor: %zu", __func__, getTimePointIn(now, timePoint),
	divisor);

	if (divisor <= 1 \|\| timePoint == 0) {
	return true;
	}

	const nsecs_t period = mRateMap[idealPeriod()].slope;
	const nsecs_t justBeforeTimePoint = timePoint - period / 2;
	const auto vsyncSequence = getVsyncSequenceLocked(justBeforeTimePoint);
	ATRACE_FORMAT_INSTANT("vsync in: %.2f sequence: %" PRId64,
	getTimePointIn(now, vsyncSequence.vsyncTime), vsyncSequence.seq);
	return vsyncSequence.seq % divisor == 0;
	}

	void VSyncPredictor::setRenderRate(Fps renderRate) {
	ATRACE_FORMAT("%s %s", __func__, to_string(renderRate).c_str());
	ALOGV("%s %s: RenderRate %s ", __func__, to_string(mId).c_str(), to_string(renderRate).c_str());
	std::lock_guard lock(mMutex);
	mRenderRateOpt = renderRate;
	}

	void VSyncPredictor::setDisplayModePtr(ftl::NonNull<DisplayModePtr> modePtr) {
	LOG_ALWAYS_FATAL_IF(mId != modePtr->getPhysicalDisplayId(),
	"mode does not belong to the display");
	ATRACE_FORMAT("%s %s", __func__, to_string(*modePtr).c_str());
	const auto timeout = modePtr->getVrrConfig()
	? modePtr->getVrrConfig()->notifyExpectedPresentConfig
	: std::nullopt;
	ALOGV("%s %s: DisplayMode %s notifyExpectedPresentTimeout %s", __func__, to_string(mId).c_str(),
	to_string(*modePtr).c_str(),
	timeout ? std::to_string(timeout->timeoutNs).c_str() : "N/A");
	std::lock_guard lock(mMutex);

	mDisplayModePtr = modePtr;
	traceInt64("VSP-setPeriod", modePtr->getVsyncRate().getPeriodNsecs());

	static constexpr size_t kSizeLimit = 30;
	if (CC_UNLIKELY(mRateMap.size() == kSizeLimit)) {
	mRateMap.erase(mRateMap.begin());
	}

	if (mRateMap.find(idealPeriod()) == mRateMap.end()) {
	mRateMap[idealPeriod()] = {idealPeriod(), 0};
	}

	clearTimestamps();
	}

	void VSyncPredictor::ensureMinFrameDurationIsKept(TimePoint expectedPresentTime,
	TimePoint lastConfirmedPresentTime) {
	const auto currentPeriod = mRateMap.find(idealPeriod())->second.slope;
	const auto threshold = currentPeriod / 2;
	const auto minFramePeriod = minFramePeriodLocked().ns();

	auto prev = lastConfirmedPresentTime.ns();
	for (auto& current : mPastExpectedPresentTimes) {
	if (CC_UNLIKELY(mTraceOn)) {
	ATRACE_FORMAT_INSTANT("current %.2f past last signaled fence",
	static_cast<float>(current.ns() - lastConfirmedPresentTime.ns()) /
	1e6f);
	}

	const auto minPeriodViolation = current.ns() - prev + threshold < minFramePeriod;
	if (minPeriodViolation) {
	ATRACE_NAME("minPeriodViolation");
	current = TimePoint::fromNs(prev + minFramePeriod);
	prev = current.ns();
	} else {
	break;
	}
	}

	if (!mPastExpectedPresentTimes.empty()) {
	const auto phase = Duration(mPastExpectedPresentTimes.back() - expectedPresentTime);
	if (phase > 0ns) {
	if (mLastVsyncSequence) {
	mLastVsyncSequence->vsyncTime += phase.ns();
	}
	mPastExpectedPresentTimes.clear();
	}
	}
	}

	void VSyncPredictor::onFrameBegin(TimePoint expectedPresentTime,
	TimePoint lastConfirmedPresentTime) {
	ATRACE_CALL();
	std::lock_guard lock(mMutex);

	if (!mDisplayModePtr->getVrrConfig()) return;

	if (CC_UNLIKELY(mTraceOn)) {
	ATRACE_FORMAT_INSTANT("vsync is %.2f past last signaled fence",
	static_cast<float>(expectedPresentTime.ns() -
	lastConfirmedPresentTime.ns()) /
	1e6f);
	}
	const auto currentPeriod = mRateMap.find(idealPeriod())->second.slope;
	const auto threshold = currentPeriod / 2;
	mPastExpectedPresentTimes.push_back(expectedPresentTime);

	while (!mPastExpectedPresentTimes.empty()) {
	const auto front = mPastExpectedPresentTimes.front().ns();
	const bool frontIsBeforeConfirmed = front < lastConfirmedPresentTime.ns() + threshold;
	if (frontIsBeforeConfirmed) {
	if (CC_UNLIKELY(mTraceOn)) {
	ATRACE_FORMAT_INSTANT("Discarding old vsync - %.2f before last signaled fence",
	static_cast<float>(lastConfirmedPresentTime.ns() - front) /
	1e6f);
	}
	mPastExpectedPresentTimes.pop_front();
	} else {
	break;
	}
	}

	ensureMinFrameDurationIsKept(expectedPresentTime, lastConfirmedPresentTime);
	}

	void VSyncPredictor::onFrameMissed(TimePoint expectedPresentTime) {
	ATRACE_CALL();

	std::lock_guard lock(mMutex);
	if (!mDisplayModePtr->getVrrConfig()) return;

	// We don't know when the frame is going to be presented, so we assume it missed one vsync
	const auto currentPeriod = mRateMap.find(idealPeriod())->second.slope;
	const auto lastConfirmedPresentTime =
	TimePoint::fromNs(expectedPresentTime.ns() + currentPeriod);

	ensureMinFrameDurationIsKept(expectedPresentTime, lastConfirmedPresentTime);
	mLastMissedVsync = expectedPresentTime;
	}

	VSyncPredictor::Model VSyncPredictor::getVSyncPredictionModel() const {
	std::lock_guard lock(mMutex);
	const auto model = VSyncPredictor::getVSyncPredictionModelLocked();
	return {model.slope, model.intercept};
	}

	VSyncPredictor::Model VSyncPredictor::getVSyncPredictionModelLocked() const {
	return mRateMap.find(idealPeriod())->second;
	}

	void VSyncPredictor::clearTimestamps() {
	ATRACE_CALL();

	if (!mTimestamps.empty()) {
	auto const maxRb = *std::max_element(mTimestamps.begin(), mTimestamps.end());
	if (mKnownTimestamp) {
	mKnownTimestamp = std::max(*mKnownTimestamp, maxRb);
	} else {
	mKnownTimestamp = maxRb;
	}

	mTimestamps.clear();
	mLastTimestampIndex = 0;
	}
	}

	bool VSyncPredictor::needsMoreSamples() const {
	std::lock_guard lock(mMutex);
	return mTimestamps.size() < kMinimumSamplesForPrediction;
	}

	void VSyncPredictor::resetModel() {
	std::lock_guard lock(mMutex);
	mRateMap[idealPeriod()] = {idealPeriod(), 0};
	clearTimestamps();
	}

	void VSyncPredictor::dump(std::string& result) const {
	std::lock_guard lock(mMutex);
	StringAppendF(&result, "\tmDisplayModePtr=%s\n", to_string(*mDisplayModePtr).c_str());
	StringAppendF(&result, "\tRefresh Rate Map:\n");
	for (const auto& [period, periodInterceptTuple] : mRateMap) {
	StringAppendF(&result,
	"\t\tFor ideal period %.2fms: period = %.2fms, intercept = %" PRId64 "\n",
	period / 1e6f, periodInterceptTuple.slope / 1e6f,
	periodInterceptTuple.intercept);
	}
	}

	} // namespace android::scheduler

	// TODO(b/129481165): remove the #pragma below and fix conversion issues
	#pragma clang diagnostic pop // ignored "-Wextra"