SF: region sampling scheduling optimization

Schedule the region sampling thread more wisely by estimating when
the next invalidate is going to happen. This makes the region sampling
to be scheduled often at times where the main thread is idle, without
eating the budget in an invalidate message.

Bug: 181983990
Test: SF unit tests
Test: observe systrace
Change-Id: I1faca3aa7f882ed7c69e77e6a0877c10d57f0f1c

1 files changed, 24 insertions, 103 deletions

diff --git a/services/surfaceflinger/RegionSamplingThread.cpp b/services/surfaceflinger/RegionSamplingThread.cpp
index 00090d948a..653aca6cde 100644
--- a/services/surfaceflinger/RegionSamplingThread.cpp
+++ b/services/surfaceflinger/RegionSamplingThread.cpp
@@ -56,16 +56,14 @@ enum class samplingStep {
     noWorkNeeded,
     idleTimerWaiting,
     waitForQuietFrame,
-    waitForZeroPhase,
     waitForSamplePhase,
     sample
 };
 
-constexpr auto timeForRegionSampling = 5000000ns;
-constexpr auto maxRegionSamplingSkips = 10;
 constexpr auto defaultRegionSamplingWorkDuration = 3ms;
 constexpr auto defaultRegionSamplingPeriod = 100ms;
 constexpr auto defaultRegionSamplingTimerTimeout = 100ms;
+constexpr auto maxRegionSamplingDelay = 100ms;
 // TODO: (b/127403193) duration to string conversion could probably be constexpr
 template <typename Rep, typename Per>
 inline std::string toNsString(std::chrono::duration<Rep, Per> t) {
@@ -99,97 +97,22 @@ RegionSamplingThread::EnvironmentTimingTunables::EnvironmentTimingTunables() {
     }
 }
 
-struct SamplingOffsetCallback : VSyncSource::Callback {
-    SamplingOffsetCallback(RegionSamplingThread& samplingThread, Scheduler& scheduler,
-                           std::chrono::nanoseconds targetSamplingWorkDuration)
-          : mRegionSamplingThread(samplingThread),
-            mTargetSamplingWorkDuration(targetSamplingWorkDuration),
-            mVSyncSource(scheduler.makePrimaryDispSyncSource("SamplingThreadDispSyncListener", 0ns,
-                                                             0ns,
-                                                             /*traceVsync=*/false)) {
-        mVSyncSource->setCallback(this);
-    }
-
-    ~SamplingOffsetCallback() { stopVsyncListener(); }
-
-    SamplingOffsetCallback(const SamplingOffsetCallback&) = delete;
-    SamplingOffsetCallback& operator=(const SamplingOffsetCallback&) = delete;
-
-    void startVsyncListener() {
-        std::lock_guard lock(mMutex);
-        if (mVsyncListening) return;
-
-        mPhaseIntervalSetting = Phase::ZERO;
-        mVSyncSource->setVSyncEnabled(true);
-        mVsyncListening = true;
-    }
-
-    void stopVsyncListener() {
-        std::lock_guard lock(mMutex);
-        stopVsyncListenerLocked();
-    }
-
-private:
-    void stopVsyncListenerLocked() /*REQUIRES(mMutex)*/ {
-        if (!mVsyncListening) return;
-
-        mVSyncSource->setVSyncEnabled(false);
-        mVsyncListening = false;
-    }
-
-    void onVSyncEvent(nsecs_t /*when*/, nsecs_t /*expectedVSyncTimestamp*/,
-                      nsecs_t /*deadlineTimestamp*/) final {
-        std::unique_lock<decltype(mMutex)> lock(mMutex);
-
-        if (mPhaseIntervalSetting == Phase::ZERO) {
-            ATRACE_INT(lumaSamplingStepTag, static_cast<int>(samplingStep::waitForSamplePhase));
-            mPhaseIntervalSetting = Phase::SAMPLING;
-            mVSyncSource->setDuration(mTargetSamplingWorkDuration, 0ns);
-            return;
-        }
-
-        if (mPhaseIntervalSetting == Phase::SAMPLING) {
-            mPhaseIntervalSetting = Phase::ZERO;
-            mVSyncSource->setDuration(0ns, 0ns);
-            stopVsyncListenerLocked();
-            lock.unlock();
-            mRegionSamplingThread.notifySamplingOffset();
-            return;
-        }
-    }
-
-    RegionSamplingThread& mRegionSamplingThread;
-    const std::chrono::nanoseconds mTargetSamplingWorkDuration;
-    mutable std::mutex mMutex;
-    enum class Phase {
-        ZERO,
-        SAMPLING
-    } mPhaseIntervalSetting /*GUARDED_BY(mMutex) macro doesnt work with unique_lock?*/
-            = Phase::ZERO;
-    bool mVsyncListening /*GUARDED_BY(mMutex)*/ = false;
-    std::unique_ptr<VSyncSource> mVSyncSource;
-};
-
-RegionSamplingThread::RegionSamplingThread(SurfaceFlinger& flinger, Scheduler& scheduler,
-                                           const TimingTunables& tunables)
+RegionSamplingThread::RegionSamplingThread(SurfaceFlinger& flinger, const TimingTunables& tunables)
       : mFlinger(flinger),
-        mScheduler(scheduler),
         mTunables(tunables),
         mIdleTimer(
                 "RegSampIdle",
                 std::chrono::duration_cast<std::chrono::milliseconds>(
                         mTunables.mSamplingTimerTimeout),
                 [] {}, [this] { checkForStaleLuma(); }),
-        mPhaseCallback(std::make_unique<SamplingOffsetCallback>(*this, mScheduler,
-                                                                tunables.mSamplingDuration)),
-        lastSampleTime(0ns) {
+        mLastSampleTime(0ns) {
     mThread = std::thread([this]() { threadMain(); });
     pthread_setname_np(mThread.native_handle(), "RegionSampling");
     mIdleTimer.start();
 }
 
-RegionSamplingThread::RegionSamplingThread(SurfaceFlinger& flinger, Scheduler& scheduler)
-      : RegionSamplingThread(flinger, scheduler,
+RegionSamplingThread::RegionSamplingThread(SurfaceFlinger& flinger)
+      : RegionSamplingThread(flinger,
                              TimingTunables{defaultRegionSamplingWorkDuration,
                                             defaultRegionSamplingPeriod,
                                             defaultRegionSamplingTimerTimeout}) {}
@@ -224,48 +147,46 @@ void RegionSamplingThread::removeListener(const sp<IRegionSamplingListener>& lis
 void RegionSamplingThread::checkForStaleLuma() {
     std::lock_guard lock(mThreadControlMutex);
 
-    if (mDiscardedFrames > 0) {
-        ATRACE_INT(lumaSamplingStepTag, static_cast<int>(samplingStep::waitForZeroPhase));
-        mDiscardedFrames = 0;
-        mPhaseCallback->startVsyncListener();
+    if (mSampleRequestTime.has_value()) {
+        ATRACE_INT(lumaSamplingStepTag, static_cast<int>(samplingStep::waitForSamplePhase));
+        mSampleRequestTime.reset();
+        mFlinger.scheduleRegionSamplingThread();
     }
 }
 
-void RegionSamplingThread::notifyNewContent() {
-    doSample();
-}
-
-void RegionSamplingThread::notifySamplingOffset() {
-    doSample();
+void RegionSamplingThread::onCompositionComplete(
+        std::optional<std::chrono::steady_clock::time_point> samplingDeadline) {
+    doSample(samplingDeadline);
 }
 
-void RegionSamplingThread::doSample() {
+void RegionSamplingThread::doSample(
+        std::optional<std::chrono::steady_clock::time_point> samplingDeadline) {
     std::lock_guard lock(mThreadControlMutex);
-    auto now = std::chrono::nanoseconds(systemTime(SYSTEM_TIME_MONOTONIC));
-    if (lastSampleTime + mTunables.mSamplingPeriod > now) {
+    const auto now = std::chrono::steady_clock::now();
+    if (mLastSampleTime + mTunables.mSamplingPeriod > now) {
+        // content changed, but we sampled not too long ago, so we need to sample some time in the
+        // future.
         ATRACE_INT(lumaSamplingStepTag, static_cast<int>(samplingStep::idleTimerWaiting));
-        if (mDiscardedFrames == 0) mDiscardedFrames++;
+        mSampleRequestTime = now;
         return;
     }
-    if (mDiscardedFrames < maxRegionSamplingSkips) {
+    if (!mSampleRequestTime.has_value() || now - *mSampleRequestTime < maxRegionSamplingDelay) {
         // If there is relatively little time left for surfaceflinger
         // until the next vsync deadline, defer this sampling work
         // to a later frame, when hopefully there will be more time.
-        const DisplayStatInfo stats = mScheduler.getDisplayStatInfo(systemTime());
-        if (std::chrono::nanoseconds(stats.vsyncTime) - now < timeForRegionSampling) {
+        if (samplingDeadline.has_value() && now + mTunables.mSamplingDuration > *samplingDeadline) {
             ATRACE_INT(lumaSamplingStepTag, static_cast<int>(samplingStep::waitForQuietFrame));
-            mDiscardedFrames++;
+            mSampleRequestTime = mSampleRequestTime.value_or(now);
             return;
         }
     }
 
     ATRACE_INT(lumaSamplingStepTag, static_cast<int>(samplingStep::sample));
 
-    mDiscardedFrames = 0;
-    lastSampleTime = now;
+    mSampleRequestTime.reset();
+    mLastSampleTime = now;
 
     mIdleTimer.reset();
-    mPhaseCallback->stopVsyncListener();
 
     mSampleRequested = true;
     mCondition.notify_one();