commit e7cc1c21a36f7906d091ca1ad57092d3ec7dd753
author Alec Mouri <alecmouri@google.com> Tue Apr 27 15:23:26 2021 -0700
committer Alec Mouri <alecmouri@google.com> Thu Apr 29 18:24:15 2021 -0700
tree 9f7b9fd0430226776e385c8f239d8c7c6c320015
parent c18151997a6608c538afb063b4e93d32a3a47adc

Dedicate a special caching slot for the layer override buffer

By using a special caching slot, this avoids import/freeBuffer churn in
the composer process which can occur when a layer is no longer using an
override buffer. Previously the layer's buffer would have been cached by
a previous setBuffer call, but since the override buffer was clobbering
a caching slot, replacing the override buffer requires re-importing the
buffer.

To resolve this, increase the size of the hwc buffer cache so it's ever
so slightly less tied to buffer queue sizes, which allows for room for
the override buffer which improves caching hit rate. On devices that
don't have layer caching turned on, this is a functional no-op because
those devices will never use the additional caching slot.

Bug: 185570241
Test: libcompositionengine_test
Test: Perfetto trace of opening and closing calculator app shows fewer
import/free buffers in the composer process

Change-Id: I219b1a1f6a31c5405736cb06d4921f300fe4a3ee

services/surfaceflinger/CompositionEngine/tests/OutputLayerTest.cpp

diff --git a/services/surfaceflinger/CompositionEngine/tests/OutputLayerTest.cpp b/services/surfaceflinger/CompositionEngine/tests/OutputLayerTest.cpp
index e876a61..3adfe40 100644
--- a/services/surfaceflinger/CompositionEngine/tests/OutputLayerTest.cpp
+++ b/services/surfaceflinger/CompositionEngine/tests/OutputLayerTest.cpp
@@ -14,6 +14,7 @@
  * limitations under the License.
  */
 
+#include <compositionengine/impl/HwcBufferCache.h>
 #include <compositionengine/impl/OutputLayer.h>
 #include <compositionengine/impl/OutputLayerCompositionState.h>
 #include <compositionengine/mock/CompositionEngine.h>
@@ -702,6 +703,7 @@
     static constexpr ui::Dataspace kOverrideDataspace = static_cast<ui::Dataspace>(72);
     static constexpr int kSupportedPerFrameMetadata = 101;
     static constexpr int kExpectedHwcSlot = 0;
+    static constexpr int kOverrideHwcSlot = impl::HwcBufferCache::FLATTENER_CACHING_SLOT;
     static constexpr bool kLayerGenericMetadata1Mandatory = true;
     static constexpr bool kLayerGenericMetadata2Mandatory = true;
 
@@ -824,10 +826,11 @@
         EXPECT_CALL(*mHwcLayer, setSidebandStream(kSidebandStreamHandle));
     }
 
-    void expectSetHdrMetadataAndBufferCalls(sp<GraphicBuffer> buffer = kBuffer,
+    void expectSetHdrMetadataAndBufferCalls(uint32_t hwcSlot = kExpectedHwcSlot,
+                                            sp<GraphicBuffer> buffer = kBuffer,
                                             sp<Fence> fence = kFence) {
         EXPECT_CALL(*mHwcLayer, setPerFrameMetadata(kSupportedPerFrameMetadata, kHdrMetadata));
-        EXPECT_CALL(*mHwcLayer, setBuffer(kExpectedHwcSlot, buffer, fence));
+        EXPECT_CALL(*mHwcLayer, setBuffer(hwcSlot, buffer, fence));
     }
 
     void expectGenericLayerMetadataCalls() {
@@ -1060,7 +1063,7 @@
                               kOverrideBlendMode, kOverrideAlpha);
     expectPerFrameCommonCalls(SimulateUnsupported::None, kOverrideDataspace, kOverrideVisibleRegion,
                               kOverrideSurfaceDamage);
-    expectSetHdrMetadataAndBufferCalls(kOverrideBuffer, kOverrideFence);
+    expectSetHdrMetadataAndBufferCalls(kOverrideHwcSlot, kOverrideBuffer, kOverrideFence);
     expectSetCompositionTypeCall(Hwc2::IComposerClient::Composition::DEVICE);
     EXPECT_CALL(*mLayerFE, hasRoundedCorners()).WillOnce(Return(false));