surfaceflinger: Use only one EventThread when phase offsets are same.

SurfaceFlinger uses two event-threads to support phase-offsets
for application and SurfaceFlinger itself. Extra thread may
cause scheduling issues and wake-up latency for either
SurfaceFlinger or Application, depending on scheduling, even
when running at higher priority as these threads have low-load
and qualify for task-packing.

Use single event-thread when phase offsets are same.

Debug runtime service call behavior change when same phase-offset:
1018 (set phase offset for Application): will change both
Application and SurfaceFlinger phase offsets.
1019 (set phase offset for SurfaceFlinger): Will be a no-op.

Change-Id: I2514b4ff6249e9bce3eb19f60b1dfe0de12b86d9

1 files changed, 18 insertions, 9 deletions

diff --git a/services/surfaceflinger/SurfaceFlinger.cpp b/services/surfaceflinger/SurfaceFlinger.cpp
index b27fc2b..43a0bd8 100644
--- a/services/surfaceflinger/SurfaceFlinger.cpp
+++ b/services/surfaceflinger/SurfaceFlinger.cpp
@@ -453,13 +453,20 @@ void SurfaceFlinger::init() {
     eglInitialize(mEGLDisplay, NULL, NULL);
 
     // start the EventThread
-    sp<VSyncSource> vsyncSrc = new DispSyncSource(&mPrimaryDispSync,
-            vsyncPhaseOffsetNs, true, "app");
-    mEventThread = new EventThread(vsyncSrc);
-    sp<VSyncSource> sfVsyncSrc = new DispSyncSource(&mPrimaryDispSync,
-            sfVsyncPhaseOffsetNs, true, "sf");
-    mSFEventThread = new EventThread(sfVsyncSrc);
-    mEventQueue.setEventThread(mSFEventThread);
+    if (vsyncPhaseOffsetNs != sfVsyncPhaseOffsetNs) {
+        sp<VSyncSource> vsyncSrc = new DispSyncSource(&mPrimaryDispSync,
+                vsyncPhaseOffsetNs, true, "app");
+        mEventThread = new EventThread(vsyncSrc);
+        sp<VSyncSource> sfVsyncSrc = new DispSyncSource(&mPrimaryDispSync,
+                sfVsyncPhaseOffsetNs, true, "sf");
+        mSFEventThread = new EventThread(sfVsyncSrc);
+        mEventQueue.setEventThread(mSFEventThread);
+    } else {
+        sp<VSyncSource> vsyncSrc = new DispSyncSource(&mPrimaryDispSync,
+                vsyncPhaseOffsetNs, true, "sf-app");
+        mEventThread = new EventThread(vsyncSrc);
+        mEventQueue.setEventThread(mEventThread);
+    }
 
     // Initialize the H/W composer object.  There may or may not be an
     // actual hardware composer underneath.
@@ -3137,12 +3144,14 @@ status_t SurfaceFlinger::onTransact(
             }
             case 1018: { // Modify Choreographer's phase offset
                 n = data.readInt32();
-                mEventThread->setPhaseOffset(static_cast<nsecs_t>(n));
+                if (mEventThread != NULL)
+                    mEventThread->setPhaseOffset(static_cast<nsecs_t>(n));
                 return NO_ERROR;
             }
             case 1019: { // Modify SurfaceFlinger's phase offset
                 n = data.readInt32();
-                mSFEventThread->setPhaseOffset(static_cast<nsecs_t>(n));
+                if (mSFEventThread != NULL)
+                    mSFEventThread->setPhaseOffset(static_cast<nsecs_t>(n));
                 return NO_ERROR;
             }
         }