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Commit c09c023a authored by Vishnu Nair's avatar Vishnu Nair
Browse files

[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
parent a0cff095

services/surfaceflinger/Layer.cpp

+4 −0
Original line number Diff line number Diff line
@@ -3037,6 +3037,10 @@ bool Layer::setBuffer(std::shared_ptr<renderengine::ExternalTexture>& buffer, 
                                      mLastClientCompositionFence);

            mLastClientCompositionFence = nullptr;

        }

    } else {

        // if we are latching a buffer for the first time then clear the mLastLatchTime since

        // we don't want to incorrectly classify a frame if we miss the desired present time.

        updateLastLatchTime(0);

    }



    mDrawingState.producerId = bufferData.producerId;

services/surfaceflinger/Layer.h

+1 −0
Original line number Diff line number Diff line
@@ -852,6 +852,7 @@ public: 
                                   const sp<GraphicBuffer>& buffer, uint64_t framenumber,

                                   const sp<Fence>& releaseFence);

    bool setFrameRateForLayerTree(FrameRate);

    bool hasBuffer() const { return mBufferInfo.mBuffer != nullptr; }



protected:

    // For unit tests

services/surfaceflinger/SurfaceFlinger.cpp

+8 −2
Original line number Diff line number Diff line
@@ -3954,9 +3954,15 @@ bool SurfaceFlinger::latchBuffers() { 
            mLayersWithQueuedFrames.emplace(sp<Layer>::fromExisting(layer));

        } else {

            layer->useEmptyDamage();

            // If the layer has frames we will update the latch time when latching the buffer.

            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;