am 50be1df7: Merge "SF: Track missed frames and optionally drop them" into mnc-dr-dev

* commit '50be1df76e2c84fc3c893ec3d3e51ba427dd3ee6':
  SF: Track missed frames and optionally drop them

services/surfaceflinger/SurfaceFlinger.cpp

@@ -163,6 +163,9 @@ SurfaceFlinger::SurfaceFlinger()
     property_get("ro.bq.gpu_to_cpu_unsupported", value, "0");
     mGpuToCpuSupported = !atoi(value);
 
+    property_get("debug.sf.drop_missed_frames", value, "0");
+    mDropMissedFrames = atoi(value);
+
     property_get("debug.sf.showupdates", value, "0");
     mDebugRegion = atoi(value);
 
@@ -919,12 +922,31 @@ bool SurfaceFlinger::handleMessageInvalidate() {
 
 void SurfaceFlinger::handleMessageRefresh() {
     ATRACE_CALL();
-    preComposition();
-    rebuildLayerStacks();
-    setUpHWComposer();
-    doDebugFlashRegions();
-    doComposition();
-    postComposition();
+
+    static nsecs_t previousExpectedPresent = 0;
+    nsecs_t expectedPresent = mPrimaryDispSync.computeNextRefresh(0);
+    static bool previousFrameMissed = false;
+    bool frameMissed = (expectedPresent == previousExpectedPresent);
+    if (frameMissed != previousFrameMissed) {
+        ATRACE_INT("FrameMissed", static_cast<int>(frameMissed));
+    }
+    previousFrameMissed = frameMissed;
+
+    if (CC_UNLIKELY(mDropMissedFrames && frameMissed)) {
+        // Latch buffers, but don't send anything to HWC, then signal another
+        // wakeup for the next vsync
+        preComposition();
+        repaintEverything();
+    } else {
+        preComposition();
+        rebuildLayerStacks();
+        setUpHWComposer();
+        doDebugFlashRegions();
+        doComposition();
+        postComposition();
+    }
+
+    previousExpectedPresent = mPrimaryDispSync.computeNextRefresh(0);
 }
 
 void SurfaceFlinger::doDebugFlashRegions()

services/surfaceflinger/SurfaceFlinger.h

@@ -445,6 +445,7 @@ private:
     RenderEngine* mRenderEngine;
     nsecs_t mBootTime;
     bool mGpuToCpuSupported;
+    bool mDropMissedFrames;
     sp<EventThread> mEventThread;
     sp<EventThread> mSFEventThread;
     sp<EventControlThread> mEventControlThread;