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/src/OutputLayer.cpp

diff --git a/services/surfaceflinger/CompositionEngine/src/OutputLayer.cpp b/services/surfaceflinger/CompositionEngine/src/OutputLayer.cpp
index cd14327..e4e46a7 100644
--- a/services/surfaceflinger/CompositionEngine/src/OutputLayer.cpp
+++ b/services/surfaceflinger/CompositionEngine/src/OutputLayer.cpp
@@ -349,7 +349,7 @@
     }
 
     writeOutputDependentPerFrameStateToHWC(hwcLayer.get());
-    writeOutputIndependentPerFrameStateToHWC(hwcLayer.get(), *outputIndependentState);
+    writeOutputIndependentPerFrameStateToHWC(hwcLayer.get(), *outputIndependentState, skipLayer);
 
     writeCompositionTypeToHWC(hwcLayer.get(), requestedCompositionType, isPeekingThrough,
                               skipLayer);
@@ -471,7 +471,8 @@
 }
 
 void OutputLayer::writeOutputIndependentPerFrameStateToHWC(
-        HWC2::Layer* hwcLayer, const LayerFECompositionState& outputIndependentState) {
+        HWC2::Layer* hwcLayer, const LayerFECompositionState& outputIndependentState,
+        bool skipLayer) {
     switch (auto error = hwcLayer->setColorTransform(outputIndependentState.colorTransform)) {
         case hal::Error::NONE:
             break;
@@ -504,7 +505,7 @@
             break;
         case hal::Composition::CURSOR:
         case hal::Composition::DEVICE:
-            writeBufferStateToHWC(hwcLayer, outputIndependentState);
+            writeBufferStateToHWC(hwcLayer, outputIndependentState, skipLayer);
             break;
         case hal::Composition::INVALID:
         case hal::Composition::CLIENT:
@@ -541,7 +542,8 @@
 }
 
 void OutputLayer::writeBufferStateToHWC(HWC2::Layer* hwcLayer,
-                                        const LayerFECompositionState& outputIndependentState) {
+                                        const LayerFECompositionState& outputIndependentState,
+                                        bool skipLayer) {
     auto supportedPerFrameMetadata =
             getOutput().getDisplayColorProfile()->getSupportedPerFrameMetadata();
     if (auto error = hwcLayer->setPerFrameMetadata(supportedPerFrameMetadata,
@@ -554,7 +556,7 @@
     sp<GraphicBuffer> buffer = outputIndependentState.buffer;
     sp<Fence> acquireFence = outputIndependentState.acquireFence;
     int slot = outputIndependentState.bufferSlot;
-    if (getState().overrideInfo.buffer != nullptr) {
+    if (getState().overrideInfo.buffer != nullptr && !skipLayer) {
         buffer = getState().overrideInfo.buffer->getBuffer();
         acquireFence = getState().overrideInfo.acquireFence;
         slot = HwcBufferCache::FLATTENER_CACHING_SLOT;