[sf] only update the last latch time if the layer has a buffer
If we apply a transaction that does not latch a buffer, we
incorrectly updated the last latch time. In the next vsync,
if we presented a buffer late, we would misclassify the
jank as buffer stuffing.
Fix this by only updating the latch time if the layer has
a buffer.
Test: verify in perfetto traces
Fixes: 270041584
Change-Id: I423a28803a2660ada80ef554469f3977c389fbfa
diff --git a/services/surfaceflinger/SurfaceFlinger.cpp b/services/surfaceflinger/SurfaceFlinger.cpp
index eecfeb6..f6063f4 100644
--- a/services/surfaceflinger/SurfaceFlinger.cpp
+++ b/services/surfaceflinger/SurfaceFlinger.cpp
@@ -3954,8 +3954,14 @@
mLayersWithQueuedFrames.emplace(sp<Layer>::fromExisting(layer));
} else {
layer->useEmptyDamage();
- // If the layer has frames we will update the latch time when latching the buffer.
- layer->updateLastLatchTime(latchTime);
+ if (!layer->hasBuffer()) {
+ // The last latch time is used to classify a missed frame as buffer stuffing
+ // instead of a missed frame. This is used to identify scenarios where we
+ // could not latch a buffer or apply a transaction due to backpressure.
+ // We only update the latch time for buffer less layers here, the latch time
+ // is updated for buffer layers when the buffer is latched.
+ layer->updateLastLatchTime(latchTime);
+ }
}
});
mForceTransactionDisplayChange = false;