SurfaceFlinger: add a sysprop for GL backpressure

In some devices where SF misses a frame in GL comp, HWC queue may
get stuffed. This causes application to block longer on dequeueBuffer
which leads to jank.

Test: 1. Open Camera
      2. Swipe horizontally to go back to previous app.

Bug: 138083790
Change-Id: I4c5963cb7ba7f9b10254c77dc7117ca3acac81cf

2 files changed, 9 insertions, 3 deletions

diff --git a/services/surfaceflinger/SurfaceFlinger.cpp b/services/surfaceflinger/SurfaceFlinger.cpp
index 2d319101b3..6166789fc4 100644
--- a/services/surfaceflinger/SurfaceFlinger.cpp
+++ b/services/surfaceflinger/SurfaceFlinger.cpp
@@ -353,6 +353,11 @@ SurfaceFlinger::SurfaceFlinger(Factory& factory) : SurfaceFlinger(factory, SkipI
     mPropagateBackpressure = !atoi(value);
     ALOGI_IF(!mPropagateBackpressure, "Disabling backpressure propagation");
 
+    property_get("debug.sf.enable_gl_backpressure", value, "0");
+    mPropagateBackpressureClientComposition = atoi(value);
+    ALOGI_IF(mPropagateBackpressureClientComposition,
+             "Enabling backpressure propagation for Client Composition");
+
     property_get("debug.sf.enable_hwc_vds", value, "0");
     mUseHwcVirtualDisplays = atoi(value);
     ALOGI_IF(mUseHwcVirtualDisplays, "Enabling HWC virtual displays");
@@ -1670,9 +1675,9 @@ void SurfaceFlinger::onMessageReceived(int32_t what) NO_THREAD_SAFETY_ANALYSIS {
                 break;
             }
 
-            // For now, only propagate backpressure when missing a hwc frame.
-            if (hwcFrameMissed && !gpuFrameMissed) {
-                if (mPropagateBackpressure) {
+            if (frameMissed && mPropagateBackpressure) {
+                if ((hwcFrameMissed && !gpuFrameMissed) ||
+                    mPropagateBackpressureClientComposition) {
                     signalLayerUpdate();
                     break;
                 }
diff --git a/services/surfaceflinger/SurfaceFlinger.h b/services/surfaceflinger/SurfaceFlinger.h
index ddfe88c928..52655944de 100644
--- a/services/surfaceflinger/SurfaceFlinger.h
+++ b/services/surfaceflinger/SurfaceFlinger.h
@@ -1003,6 +1003,7 @@ private:
     volatile nsecs_t mDebugInTransaction = 0;
     bool mForceFullDamage = false;
     bool mPropagateBackpressure = true;
+    bool mPropagateBackpressureClientComposition = false;
     std::unique_ptr<SurfaceInterceptor> mInterceptor;
     SurfaceTracing mTracing{*this};
     bool mTracingEnabled = false;