HWC2: Backpressure missed vsyncs into apps
Adds a mechanism to detect whether the prior frame SurfaceFlinger
presented to hardware composer was actually picked up or not. We then
use this mechanism to avoid pushing two frames in the same vsync.
This backpressure is passed back to applications by not latching any
buffers, which will manifest as dequeueBuffer stalling until
SurfaceFlinger releases a buffer on the following vsync.
Also makes the former INVALIDATE_ON_VSYNC behavior the only behavior
so that this functionality works correctly.
Bug: 29413700
Change-Id: Ibde358e45423ee6fea7b5e09ff65e49c4ad67baa
diff --git a/services/surfaceflinger/SurfaceFlinger.h b/services/surfaceflinger/SurfaceFlinger.h
index 28666e2..0df39a4 100644
--- a/services/surfaceflinger/SurfaceFlinger.h
+++ b/services/surfaceflinger/SurfaceFlinger.h
@@ -468,7 +468,6 @@
RenderEngine* mRenderEngine;
nsecs_t mBootTime;
bool mGpuToCpuSupported;
- bool mDropMissedFrames;
sp<EventThread> mEventThread;
sp<EventThread> mSFEventThread;
sp<EventControlThread> mEventControlThread;
@@ -488,6 +487,8 @@
bool mAnimCompositionPending;
#ifdef USE_HWC2
std::vector<sp<Layer>> mLayersWithQueuedFrames;
+ sp<Fence> mPreviousPresentFence = Fence::NO_FENCE;
+ bool mHadClientComposition = false;
#endif
// this may only be written from the main thread with mStateLock held