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* Copyright 2018 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
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* See the License for the specific language governing permissions and
* limitations under the License.
#pragma once
#include <chrono>
#include <mutex>
#include "Scheduler.h"
namespace android::scheduler {
* Modulates the vsync-offsets depending on current SurfaceFlinger state.
class VSyncModulator {
// Number of frames we'll keep the early phase offsets once they are activated for a
// transaction. This acts as a low-pass filter in case the client isn't quick enough in
// sending new transactions.
static constexpr int MIN_EARLY_FRAME_COUNT_TRANSACTION = 2;
// Number of frames we'll keep the early gl phase offsets once they are activated.
// This acts as a low-pass filter to avoid scenarios where we rapidly
// switch in and out of gl composition.
static constexpr int MIN_EARLY_GL_FRAME_COUNT_TRANSACTION = 2;
// Margin used to account for potential data races
static const constexpr std::chrono::nanoseconds MARGIN_FOR_TX_APPLY = 1ms;
// Wrapper for a collection of surfaceflinger/app offsets for a particular
// configuration.
struct Offsets {
nsecs_t sf;
nsecs_t app;
bool operator==(const Offsets& other) const { return sf == other.sf && app ==; }
bool operator!=(const Offsets& other) const { return !(*this == other); }
struct OffsetsConfig {
Offsets early; // For transactions with the eEarlyWakeup flag.
Offsets earlyGl; // As above but while compositing with GL.
Offsets late; // Default.
bool operator==(const OffsetsConfig& other) const {
return early == other.early && earlyGl == other.earlyGl && late == other.late;
bool operator!=(const OffsetsConfig& other) const { return !(*this == other); }
VSyncModulator(IPhaseOffsetControl&, ConnectionHandle appConnectionHandle,
ConnectionHandle sfConnectionHandle, const OffsetsConfig&);
void setPhaseOffsets(const OffsetsConfig&) EXCLUDES(mMutex);
// Signals that a transaction has started, and changes offsets accordingly.
void setTransactionStart(Scheduler::TransactionStart transactionStart);
// Signals that a transaction has been completed, so that we can finish
// special handling for a transaction.
void onTransactionHandled();
// Called when we send a refresh rate change to hardware composer, so that
// we can move into early offsets.
void onRefreshRateChangeInitiated();
// Called when we detect from vsync signals that the refresh rate changed.
// This way we can move out of early offsets if no longer necessary.
void onRefreshRateChangeCompleted();
// Called when the display is presenting a new frame. usedRenderEngine
// should be set to true if RenderEngine was involved with composing the new
// frame.
void onRefreshed(bool usedRenderEngine);
// Returns the offsets that we are currently using
Offsets getOffsets() const EXCLUDES(mMutex);
friend class VSyncModulatorTest;
// Returns the next offsets that we should be using
const Offsets& getNextOffsets() const REQUIRES(mMutex);
// Updates offsets and persists them into the scheduler framework.
void updateOffsets() EXCLUDES(mMutex);
void updateOffsetsLocked() REQUIRES(mMutex);
IPhaseOffsetControl& mPhaseOffsetControl;
const ConnectionHandle mAppConnectionHandle;
const ConnectionHandle mSfConnectionHandle;
mutable std::mutex mMutex;
OffsetsConfig mOffsetsConfig GUARDED_BY(mMutex);
Offsets mOffsets GUARDED_BY(mMutex){mOffsetsConfig.late};
std::atomic<Scheduler::TransactionStart> mTransactionStart =
std::atomic<bool> mRefreshRateChangePending = false;
std::atomic<bool> mExplicitEarlyWakeup = false;
std::atomic<int> mRemainingEarlyFrameCount = 0;
std::atomic<int> mRemainingRenderEngineUsageCount = 0;
std::atomic<std::chrono::steady_clock::time_point> mEarlyTxnStartTime = {};
std::atomic<std::chrono::steady_clock::time_point> mTxnAppliedTime = {};
bool mTraceDetailedInfo = false;
} // namespace android::scheduler