commit 96ca45c4b168e1463e9b1e4d0bb2e2fda35f7edb
author Alec Mouri <alecmouri@google.com> Wed Jun 09 17:32:26 2021 -0700
committer Alec Mouri <alecmouri@google.com> Thu Jun 10 16:57:24 2021 -0700
tree 5584aff39aa49f7f9fe16c553100d19c264d6ba5
parent cda04d4f37869ee98caa9df3c865c98e3e4c8ca4

Don't send override buffer down to HWC if the layer would be skipped

Consider a set of five cached layers. Because ComposerResources' caches
are scoped per-layer and does not globally track buffers, the override
buffer for each layer needs to be re-imported, and a previous override
buffer needs to be freed, if the new override buffer changed between
frames. This causes a lot of churn in validate(), up to double CPU time
in the hot path.

Instead, we shouldn't override the buffer if a layer would be skipped.
In the aforementioned example, this would cause 1 buffers-worth of chrun
when importing, rather than 5.

Bug: 190654391
Test: Perfetto trace
Change-Id: I907b0c4c340fd99a0023429a8ad740ecc9208815

services/surfaceflinger/CompositionEngine/tests/OutputLayerTest.cpp

diff --git a/services/surfaceflinger/CompositionEngine/tests/OutputLayerTest.cpp b/services/surfaceflinger/CompositionEngine/tests/OutputLayerTest.cpp
index 5bd1216..e9ecf3e 100644
--- a/services/surfaceflinger/CompositionEngine/tests/OutputLayerTest.cpp
+++ b/services/surfaceflinger/CompositionEngine/tests/OutputLayerTest.cpp
@@ -699,6 +699,7 @@
             Hwc2::IComposerClient::BlendMode::PREMULTIPLIED;
     static constexpr float kAlpha = 51.f;
     static constexpr float kOverrideAlpha = 1.f;
+    static constexpr float kSkipAlpha = 0.f;
     static constexpr ui::Dataspace kDataspace = static_cast<ui::Dataspace>(71);
     static constexpr ui::Dataspace kOverrideDataspace = static_cast<ui::Dataspace>(72);
     static constexpr int kSupportedPerFrameMetadata = 101;
@@ -1055,6 +1056,22 @@
                                  /*zIsOverridden*/ false, /*isPeekingThrough*/ false);
 }
 
+TEST_F(OutputLayerWriteStateToHWCTest, overriddenSkipLayerDoesNotSendBuffer) {
+    mLayerFEState.compositionType = Hwc2::IComposerClient::Composition::DEVICE;
+    includeOverrideInfo();
+
+    expectGeometryCommonCalls(kOverrideDisplayFrame, kOverrideSourceCrop, kOverrideBufferTransform,
+                              kOverrideBlendMode, kSkipAlpha);
+    expectPerFrameCommonCalls(SimulateUnsupported::None, kOverrideDataspace, kOverrideVisibleRegion,
+                              kOverrideSurfaceDamage);
+    expectSetHdrMetadataAndBufferCalls();
+    expectSetCompositionTypeCall(Hwc2::IComposerClient::Composition::DEVICE);
+    EXPECT_CALL(*mLayerFE, hasRoundedCorners()).WillRepeatedly(Return(false));
+
+    mOutputLayer.writeStateToHWC(/*includeGeometry*/ true, /*skipLayer*/ true, 0,
+                                 /*zIsOverridden*/ false, /*isPeekingThrough*/ false);
+}
+
 TEST_F(OutputLayerWriteStateToHWCTest, includesOverrideInfoIfPresent) {
     mLayerFEState.compositionType = Hwc2::IComposerClient::Composition::DEVICE;
     includeOverrideInfo();