commit 167bdde88b9159c62c5c4d839e7615c94e7851dc
author Robert Carr <racarr@google.com> Wed Jul 28 11:26:51 2021 -0700
committer Rob Carr <racarr@google.com> Wed Jul 28 22:38:15 2021 +0000
tree 27849230e2b6070a22ad6b86f3dd08d861154f40
parent 6a409e17600f320134dea722247c15770030d7b2

Prevent HDRLayerInfoListener traversal from running on every frame

We should only have to update the HDRLayerInfoListener in a few
scenarios.
    1. A new listener appeared
    2. A buffer changed colorspace
    3. Surface geometry (visibility, parenting, display, etc) changed
We protect the traversal behind these flags to avoid the runtime in the
hot path of continuous buffer updates. A follow up fix could consider
directly recursively traversing and early returning if !Layer->isVisible.

Bug: 186200583
Test: Existing tests pass, simpleperf
Change-Id: I549fdf6ea228344f79f6989b86b8e73a6065158a

services/surfaceflinger/SurfaceFlinger.cpp

diff --git a/services/surfaceflinger/SurfaceFlinger.cpp b/services/surfaceflinger/SurfaceFlinger.cpp
index 7270016..76221bc 100644
--- a/services/surfaceflinger/SurfaceFlinger.cpp
+++ b/services/surfaceflinger/SurfaceFlinger.cpp
@@ -1643,6 +1643,9 @@
         hdrInfoReporter = sp<HdrLayerInfoReporter>::make();
     }
     hdrInfoReporter->addListener(listener);
+
+
+    mAddingHDRLayerInfoListener = true;
     return OK;
 }
 
@@ -2143,6 +2146,8 @@
             mTracing.notify("bufferLatched");
         }
     }
+
+    mVisibleRegionsWereDirtyThisFrame = mVisibleRegionsDirty; // Cache value for use in post-comp
     mVisibleRegionsDirty = false;
 
     if (mCompositionEngine->needsAnotherUpdate()) {
@@ -2287,6 +2292,7 @@
 
     std::vector<std::pair<std::shared_ptr<compositionengine::Display>, sp<HdrLayerInfoReporter>>>
             hdrInfoListeners;
+    bool haveNewListeners = false;
     {
         Mutex::Autolock lock(mStateLock);
         if (mFpsReporter) {
@@ -2304,37 +2310,45 @@
                 }
             }
         }
+        haveNewListeners = mAddingHDRLayerInfoListener; // grab this with state lock
+        mAddingHDRLayerInfoListener = false;
     }
 
-    for (auto& [compositionDisplay, listener] : hdrInfoListeners) {
-        HdrLayerInfoReporter::HdrLayerInfo info;
-        int32_t maxArea = 0;
-        mDrawingState.traverse([&, compositionDisplay = compositionDisplay](Layer* layer) {
-            const auto layerFe = layer->getCompositionEngineLayerFE();
-            if (layer->isVisible() && compositionDisplay->belongsInOutput(layerFe)) {
-                const Dataspace transfer =
+    if (haveNewListeners || mSomeDataspaceChanged || mVisibleRegionsWereDirtyThisFrame) {
+        for (auto& [compositionDisplay, listener] : hdrInfoListeners) {
+            HdrLayerInfoReporter::HdrLayerInfo info;
+            int32_t maxArea = 0;
+            mDrawingState.traverse([&, compositionDisplay = compositionDisplay](Layer* layer) {
+                const auto layerFe = layer->getCompositionEngineLayerFE();
+                if (layer->isVisible() && compositionDisplay->belongsInOutput(layerFe)) {
+                    const Dataspace transfer =
                         static_cast<Dataspace>(layer->getDataSpace() & Dataspace::TRANSFER_MASK);
-                const bool isHdr = (transfer == Dataspace::TRANSFER_ST2084 ||
-                                    transfer == Dataspace::TRANSFER_HLG);
+                    const bool isHdr = (transfer == Dataspace::TRANSFER_ST2084 ||
+                                        transfer == Dataspace::TRANSFER_HLG);
 
-                if (isHdr) {
-                    const auto* outputLayer = compositionDisplay->getOutputLayerForLayer(layerFe);
-                    if (outputLayer) {
-                        info.numberOfHdrLayers++;
-                        const auto displayFrame = outputLayer->getState().displayFrame;
-                        const int32_t area = displayFrame.width() * displayFrame.height();
-                        if (area > maxArea) {
-                            maxArea = area;
-                            info.maxW = displayFrame.width();
-                            info.maxH = displayFrame.height();
+                    if (isHdr) {
+                        const auto* outputLayer =
+                            compositionDisplay->getOutputLayerForLayer(layerFe);
+                        if (outputLayer) {
+                            info.numberOfHdrLayers++;
+                            const auto displayFrame = outputLayer->getState().displayFrame;
+                            const int32_t area = displayFrame.width() * displayFrame.height();
+                            if (area > maxArea) {
+                                maxArea = area;
+                                info.maxW = displayFrame.width();
+                                info.maxH = displayFrame.height();
+                            }
                         }
                     }
                 }
-            }
-        });
-        listener->dispatchHdrLayerInfo(info);
+            });
+            listener->dispatchHdrLayerInfo(info);
+        }
     }
 
+    mSomeDataspaceChanged = false;
+    mVisibleRegionsWereDirtyThisFrame = false;
+
     mTransactionCallbackInvoker.addPresentFence(mPreviousPresentFences[0].fence);
     mTransactionCallbackInvoker.sendCallbacks();