From e524dd9d136049bbca78c2e148b5556ad3c128eb Mon Sep 17 00:00:00 2001
From: Melody Hsu <melodymhsu@google.com>
Date: Tue, 27 Aug 2024 22:27:29 +0000
Subject: Recover from buffer stuffing for canned animations

Buffer stuffing occurs when SurfaceFlinger misses a frame, but the
client continues to produce buffers at the same rate, causing a
greater risk for jank to occur. Recovery is achieved for canned
animations by adjusting the animation timeline on the client side so
that SurfaceFlinger is no longer behind.

Use SF backdoor command 1045 to inject jank.
Usage: adb shell service call SurfaceFlinger 1045 f 1

Bug: b/294922229
Test: atest EventThreadTest
Test: presubmit, manually check perfetto traces
Flag: android.view.flags.buffer_stuffing_recovery
Change-Id: I38f0eb3d6ef1331e07d6022fa3a0e16c556ba06f
---
 services/surfaceflinger/SurfaceFlinger.cpp | 30 ++++++++++++++++++++++++++++++
 1 file changed, 30 insertions(+)

(limited to 'services/surfaceflinger/SurfaceFlinger.cpp')

diff --git a/services/surfaceflinger/SurfaceFlinger.cpp b/services/surfaceflinger/SurfaceFlinger.cpp
index d35a76ad4b..c0eade840b 100644
--- a/services/surfaceflinger/SurfaceFlinger.cpp
+++ b/services/surfaceflinger/SurfaceFlinger.cpp
@@ -64,11 +64,13 @@
 #include <ftl/concat.h>
 #include <ftl/fake_guard.h>
 #include <ftl/future.h>
+#include <ftl/small_map.h>
 #include <ftl/unit.h>
 #include <gui/AidlUtil.h>
 #include <gui/BufferQueue.h>
 #include <gui/DebugEGLImageTracker.h>
 #include <gui/IProducerListener.h>
+#include <gui/JankInfo.h>
 #include <gui/LayerMetadata.h>
 #include <gui/LayerState.h>
 #include <gui/Surface.h>
@@ -3066,12 +3068,40 @@ void SurfaceFlinger::onCompositionPresented(PhysicalDisplayId pacesetterId,
 
     const TimePoint presentTime = TimePoint::now();
 
+    // The Uids of layer owners that are in buffer stuffing mode, and their elevated
+    // buffer counts. Messages to start recovery are sent exclusively to these Uids.
+    BufferStuffingMap bufferStuffedUids;
+
     // Set presentation information before calling Layer::releasePendingBuffer, such that jank
     // information from previous' frame classification is already available when sending jank info
     // to clients, so they get jank classification as early as possible.
     mFrameTimeline->setSfPresent(presentTime.ns(), pacesetterPresentFenceTime,
                                  pacesetterGpuCompositionDoneFenceTime);
 
+    // Find and register any layers that are in buffer stuffing mode
+    const auto& presentFrames = mFrameTimeline->getPresentFrames();
+
+    for (const auto& frame : presentFrames) {
+        const auto& layer = mLayerLifecycleManager.getLayerFromId(frame->getLayerId());
+        if (!layer) continue;
+        uint32_t numberQueuedBuffers = layer->pendingBuffers ? layer->pendingBuffers->load() : 0;
+        int32_t jankType = frame->getJankType().value_or(JankType::None);
+        if (jankType & JankType::BufferStuffing &&
+            layer->flags & layer_state_t::eRecoverableFromBufferStuffing) {
+            auto [it, wasEmplaced] =
+                    bufferStuffedUids.try_emplace(layer->ownerUid.val(), numberQueuedBuffers);
+            // Update with maximum number of queued buffers, allows clients drawing
+            // multiple windows to account for the most severely stuffed window
+            if (!wasEmplaced && it->second < numberQueuedBuffers) {
+                it->second = numberQueuedBuffers;
+            }
+        }
+    }
+
+    if (!bufferStuffedUids.empty()) {
+        mScheduler->addBufferStuffedUids(std::move(bufferStuffedUids));
+    }
+
     // We use the CompositionEngine::getLastFrameRefreshTimestamp() which might
     // be sampled a little later than when we started doing work for this frame,
     // but that should be okay since CompositorTiming has snapping logic.
-- 
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