Evicting unused cache entries before RasterCache actions (flutter#34627)

Author: ColdPaleLight

flow/frame_timings_recorder_unittests.cc

@@ -91,7 +91,7 @@ TEST(FrameTimingsRecorderTest, RecordRasterTimesWithCache) {
   using namespace std::chrono_literals;
 
   MockRasterCache cache(1, 10);
-  cache.PrepareNewFrame();
+  cache.BeginFrame();
 
   const auto raster_start = fml::TimePoint::Now();
   recorder->RecordRasterStart(raster_start);
@@ -102,8 +102,9 @@ TEST(FrameTimingsRecorderTest, RecordRasterTimesWithCache) {
   cache.AddMockPicture(100, 100);
   size_t picture_bytes = cache.EstimatePictureCacheByteSize();
   EXPECT_GT(picture_bytes, 0u);
+  cache.EvictUnusedCacheEntries();
 
-  cache.CleanupAfterFrame();
+  cache.EndFrame();
 
   const auto before_raster_end_wall_time = fml::TimePoint::CurrentWallTime();
   std::this_thread::sleep_for(1ms);
@@ -252,7 +253,7 @@ TEST(FrameTimingsRecorderTest, ClonedHasSameRasterEnd) {
 TEST(FrameTimingsRecorderTest, ClonedHasSameRasterEndWithCache) {
   auto recorder = std::make_unique<FrameTimingsRecorder>();
   MockRasterCache cache(1, 10);
-  cache.PrepareNewFrame();
+  cache.BeginFrame();
 
   const auto now = fml::TimePoint::Now();
   recorder->RecordVsync(now, now + fml::TimeDelta::FromMilliseconds(16));
@@ -266,8 +267,8 @@ TEST(FrameTimingsRecorderTest, ClonedHasSameRasterEndWithCache) {
   cache.AddMockPicture(100, 100);
   size_t picture_bytes = cache.EstimatePictureCacheByteSize();
   EXPECT_GT(picture_bytes, 0u);
-
-  cache.CleanupAfterFrame();
+  cache.EvictUnusedCacheEntries();
+  cache.EndFrame();
   recorder->RecordRasterEnd(&cache);
 
   auto cloned = recorder->CloneUntil(FrameTimingsRecorder::State::kRasterEnd);

flow/layers/container_layer_unittests.cc

@@ -268,8 +268,9 @@ TEST_F(ContainerLayerTest, RasterCacheTest) {
   {
     // frame1
     use_mock_raster_cache();
-    preroll_context()->raster_cache->PrepareNewFrame();
+    preroll_context()->raster_cache->BeginFrame();
     layer->Preroll(preroll_context(), SkMatrix::I());
+    preroll_context()->raster_cache->EvictUnusedCacheEntries();
     // Cache the cacheable entries
     LayerTree::TryToRasterCache(*(preroll_context()->raster_cached_entries),
                                 &paint_context());
@@ -299,16 +300,17 @@ TEST_F(ContainerLayerTest, RasterCacheTest) {
     // render count < 2 don't cache it
     EXPECT_EQ(cacheable_container_layer2->raster_cache_item()->cache_state(),
               RasterCacheItem::CacheState::kNone);
-    preroll_context()->raster_cache->CleanupAfterFrame();
+    preroll_context()->raster_cache->EndFrame();
   }
 
   {
     // frame2
     // new frame the layer tree will create new PrerollContext, so in here we
     // clear the cached_entries
     preroll_context()->raster_cached_entries->clear();
-    preroll_context()->raster_cache->PrepareNewFrame();
+    preroll_context()->raster_cache->BeginFrame();
     layer->Preroll(preroll_context(), SkMatrix::I());
+    preroll_context()->raster_cache->EvictUnusedCacheEntries();
 
     // Cache the cacheable entries
     LayerTree::TryToRasterCache(*(preroll_context()->raster_cached_entries),
@@ -342,17 +344,17 @@ TEST_F(ContainerLayerTest, RasterCacheTest) {
     EXPECT_TRUE(raster_cache()->Draw(
         cacheable_layer21->raster_cache_item()->GetId().value(), cache_canvas,
         &paint));
-    preroll_context()->raster_cache->CleanupAfterFrame();
+    preroll_context()->raster_cache->EndFrame();
   }
 
   {
     // frame3
     // new frame the layer tree will create new PrerollContext, so in here we
     // clear the cached_entries
-    preroll_context()->raster_cache->PrepareNewFrame();
+    preroll_context()->raster_cache->BeginFrame();
     preroll_context()->raster_cached_entries->clear();
     layer->Preroll(preroll_context(), SkMatrix::I());
-
+    preroll_context()->raster_cache->EvictUnusedCacheEntries();
     // Cache the cacheable entries
     LayerTree::TryToRasterCache(*(preroll_context()->raster_cached_entries),
                                 &paint_context());
@@ -385,33 +387,34 @@ TEST_F(ContainerLayerTest, RasterCacheTest) {
     EXPECT_TRUE(raster_cache()->HasEntry(
         cacheable_layer21->raster_cache_item()->GetId().value(),
         SkMatrix::I()));
-    preroll_context()->raster_cache->CleanupAfterFrame();
+    preroll_context()->raster_cache->EndFrame();
   }
 
   {
-    preroll_context()->raster_cache->PrepareNewFrame();
+    preroll_context()->raster_cache->BeginFrame();
     // frame4
     preroll_context()->raster_cached_entries->clear();
     layer->Preroll(preroll_context(), SkMatrix::I());
+    preroll_context()->raster_cache->EvictUnusedCacheEntries();
     LayerTree::TryToRasterCache(*(preroll_context()->raster_cached_entries),
                                 &paint_context());
-    preroll_context()->raster_cache->CleanupAfterFrame();
+    preroll_context()->raster_cache->EndFrame();
 
     // frame5
-    preroll_context()->raster_cache->PrepareNewFrame();
+    preroll_context()->raster_cache->BeginFrame();
     preroll_context()->raster_cached_entries->clear();
     layer->Preroll(preroll_context(), SkMatrix::I());
     LayerTree::TryToRasterCache(*(preroll_context()->raster_cached_entries),
                                 &paint_context());
-    preroll_context()->raster_cache->CleanupAfterFrame();
+    preroll_context()->raster_cache->EndFrame();
 
     // frame6
-    preroll_context()->raster_cache->PrepareNewFrame();
+    preroll_context()->raster_cache->BeginFrame();
     preroll_context()->raster_cached_entries->clear();
     layer->Preroll(preroll_context(), SkMatrix::I());
     LayerTree::TryToRasterCache(*(preroll_context()->raster_cached_entries),
                                 &paint_context());
-    preroll_context()->raster_cache->CleanupAfterFrame();
+    preroll_context()->raster_cache->EndFrame();
   }
 }
 

flow/layers/layer_tree.cc

@@ -150,6 +150,7 @@ void LayerTree::Paint(CompositorContext::ScopedFrame& frame,
   };
 
   if (cache) {
+    cache->EvictUnusedCacheEntries();
     TryToRasterCache(raster_cache_items_, &context, ignore_raster_cache);
   }
 

flow/raster_cache.cc

@@ -171,58 +171,47 @@ bool RasterCache::Draw(const RasterCacheKeyID& id,
   return false;
 }
 
-void RasterCache::PrepareNewFrame() {
+void RasterCache::BeginFrame() {
   display_list_cached_this_frame_ = 0;
+  picture_metrics_ = {};
+  layer_metrics_ = {};
 }
 
-void RasterCache::SweepOneCacheAfterFrame(RasterCacheKey::Map<Entry>& cache,
-                                          RasterCacheMetrics& picture_metrics,
-                                          RasterCacheMetrics& layer_metrics) {
+void RasterCache::UpdateMetrics() {
+  for (auto it = cache_.begin(); it != cache_.end(); ++it) {
+    Entry& entry = it->second;
+    FML_DCHECK(entry.encountered_this_frame);
+    if (entry.image) {
+      RasterCacheMetrics& metrics = GetMetricsForKind(it->first.kind());
+      metrics.in_use_count++;
+      metrics.in_use_bytes += entry.image->image_bytes();
+    }
+    entry.encountered_this_frame = false;
+  }
+}
+
+void RasterCache::EvictUnusedCacheEntries() {
   std::vector<RasterCacheKey::Map<Entry>::iterator> dead;
 
-  for (auto it = cache.begin(); it != cache.end(); ++it) {
+  for (auto it = cache_.begin(); it != cache_.end(); ++it) {
     Entry& entry = it->second;
-
     if (!entry.encountered_this_frame) {
       dead.push_back(it);
-    } else if (entry.image) {
-      RasterCacheKeyKind kind = it->first.kind();
-      switch (kind) {
-        case RasterCacheKeyKind::kDisplayListMetrics:
-          picture_metrics.in_use_count++;
-          picture_metrics.in_use_bytes += entry.image->image_bytes();
-          break;
-        case RasterCacheKeyKind::kLayerMetrics:
-          layer_metrics.in_use_count++;
-          layer_metrics.in_use_bytes += entry.image->image_bytes();
-          break;
-      }
     }
-    entry.encountered_this_frame = false;
   }
 
   for (auto it : dead) {
     if (it->second.image) {
-      RasterCacheKeyKind kind = it->first.kind();
-      switch (kind) {
-        case RasterCacheKeyKind::kDisplayListMetrics:
-          picture_metrics.eviction_count++;
-          picture_metrics.eviction_bytes += it->second.image->image_bytes();
-          break;
-        case RasterCacheKeyKind::kLayerMetrics:
-          layer_metrics.eviction_count++;
-          layer_metrics.eviction_bytes += it->second.image->image_bytes();
-          break;
-      }
+      RasterCacheMetrics& metrics = GetMetricsForKind(it->first.kind());
+      metrics.eviction_count++;
+      metrics.eviction_bytes += it->second.image->image_bytes();
     }
-    cache.erase(it);
+    cache_.erase(it);
   }
 }
 
-void RasterCache::CleanupAfterFrame() {
-  picture_metrics_ = {};
-  layer_metrics_ = {};
-  SweepOneCacheAfterFrame(cache_, picture_metrics_, layer_metrics_);
+void RasterCache::EndFrame() {
+  UpdateMetrics();
   TraceStatsToTimeline();
 }
 
@@ -303,4 +292,13 @@ size_t RasterCache::EstimatePictureCacheByteSize() const {
   return picture_cache_bytes;
 }
 
+RasterCacheMetrics& RasterCache::GetMetricsForKind(RasterCacheKeyKind kind) {
+  switch (kind) {
+    case RasterCacheKeyKind::kDisplayListMetrics:
+      return picture_metrics_;
+    case RasterCacheKeyKind::kLayerMetrics:
+      return layer_metrics_;
+  }
+}
+
 }  // namespace flutter

flow/raster_cache.h

@@ -78,20 +78,40 @@ struct RasterCacheMetrics {
   size_t in_use_bytes = 0;
 
   /**
-   * The total cache entries that had images during this frame whether
-   * they were used in the frame or held memory during the frame and then
-   * were evicted after it ended.
+   * The total cache entries that had images during this frame.
    */
-  size_t total_count() const { return in_use_count + eviction_count; }
+  size_t total_count() const { return in_use_count; }
 
   /**
-   * The size of all of the cached images during this frame whether
-   * they were used in the frame or held memory during the frame and then
-   * were evicted after it ended.
+   * The size of all of the cached images during this frame.
    */
-  size_t total_bytes() const { return in_use_bytes + eviction_bytes; }
+  size_t total_bytes() const { return in_use_bytes; }
 };
 
+/**
+ * RasterCache is used to cache rasterized layers or display lists to improve
+ * performance.
+ *
+ * Life cycle of RasterCache methods:
+ * - Preroll stage
+ *   - LayerTree::Preroll - for each Layer in the tree:
+ *     - RasterCacheItem::PrerollSetup
+ *         At the start of each layer's preroll, add cache items to
+ *         `PrerollContext::raster_cached_entries`.
+ *     - RasterCacheItem::PrerollFinalize
+ *         At the end of each layer's preroll, may mark cache entris as
+ *         encountered by the current frame.
+ * - Paint stage
+ *   - RasterCache::EvictUnusedCacheEntries
+ *       Evit cached images that are no longer used.
+ *   - LayerTree::TryToPrepareRasterCache
+ *       Create cache image for each cache entry if it does not exist.
+ *   - LayerTree::Paint - for each layer in the tree:
+ *       If layers or display lists are cached as cached images, the method
+ *       `RasterCache::Draw` will be used to draw those cache images.
+ *   - RasterCache::EndFrame:
+ *       Computes used counts and memory then reports cache metrics.
+ */
 class RasterCache {
  public:
   struct Context {
@@ -126,9 +146,11 @@ class RasterCache {
 
   bool HasEntry(const RasterCacheKeyID& id, const SkMatrix&) const;
 
-  void PrepareNewFrame();
+  void BeginFrame();
 
-  void CleanupAfterFrame();
+  void EvictUnusedCacheEntries();
+
+  void EndFrame();
 
   void Clear();
 
@@ -222,9 +244,9 @@ class RasterCache {
     std::unique_ptr<RasterCacheResult> image;
   };
 
-  void SweepOneCacheAfterFrame(RasterCacheKey::Map<Entry>& cache,
-                               RasterCacheMetrics& picture_metrics,
-                               RasterCacheMetrics& layer_metrics);
+  void UpdateMetrics();
+
+  RasterCacheMetrics& GetMetricsForKind(RasterCacheKeyKind kind);
 
   const size_t access_threshold_;
   const size_t display_list_cache_limit_per_frame_;