[WIP]RasterCache adds a new mechanism for particularly complex pictures or display lists

flow/raster_cache.cc

@@ -180,6 +180,7 @@ void RasterCache::Prepare(PrerollContext* context,
   Entry& entry = cache_[cache_key];
   entry.access_count++;
   entry.used_this_frame = true;
+  entry.unused_count = 0;
   if (!entry.image) {
     entry.image = RasterizeLayer(context, layer, ctm, checkerboard_images_);
   }
@@ -222,7 +223,8 @@ bool RasterCache::Prepare(PrerollContext* context,
                           bool is_complex,
                           bool will_change,
                           const SkMatrix& untranslated_matrix,
-                          const SkPoint& offset) {
+                          const SkPoint& offset,
+                          bool is_high_priority) {
   if (!GenerateNewCacheInThisFrame()) {
     return false;
   }
@@ -245,7 +247,8 @@ bool RasterCache::Prepare(PrerollContext* context,
 
   // Creates an entry, if not present prior.
   Entry& entry = cache_[cache_key];
-  if (entry.access_count < access_threshold_) {
+  entry.is_high_priority = is_high_priority;
+  if (!is_high_priority && entry.access_count < access_threshold_) {
     // Frame threshold has not yet been reached.
     return false;
   }
@@ -270,7 +273,8 @@ bool RasterCache::Prepare(PrerollContext* context,
                           bool is_complex,
                           bool will_change,
                           const SkMatrix& untranslated_matrix,
-                          const SkPoint& offset) {
+                          const SkPoint& offset,
+                          bool is_high_priority) {
   if (!GenerateNewCacheInThisFrame()) {
     return false;
   }
@@ -300,7 +304,8 @@ bool RasterCache::Prepare(PrerollContext* context,
 
   // Creates an entry, if not present prior.
   Entry& entry = cache_[cache_key];
-  if (entry.access_count < access_threshold_) {
+  entry.is_high_priority = is_high_priority;
+  if (!is_high_priority && entry.access_count < access_threshold_) {
     // Frame threshold has not yet been reached.
     return false;
   }
@@ -345,6 +350,7 @@ void RasterCache::Touch(const RasterCacheKey& cache_key) {
   if (it != cache_.end()) {
     it->second.used_this_frame = true;
     it->second.access_count++;
+    it->second.unused_count = 0;
   }
 }
 
@@ -384,6 +390,7 @@ bool RasterCache::Draw(const RasterCacheKey& cache_key,
   Entry& entry = it->second;
   entry.access_count++;
   entry.used_this_frame = true;
+  entry.unused_count = 0;
 
   if (entry.image) {
     entry.image->draw(canvas, paint);
@@ -398,47 +405,37 @@ void RasterCache::PrepareNewFrame() {
   display_list_cached_this_frame_ = 0;
 }
 
-void RasterCache::SweepOneCacheAfterFrame(RasterCacheKey::Map<Entry>& cache,
-                                          RasterCacheMetrics& picture_metrics,
-                                          RasterCacheMetrics& layer_metrics) {
+void RasterCache::SweepCacheAfterFrame() {
   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.used_this_frame) {
-      dead.push_back(it);
-    } else if (entry.image) {
-      RasterCacheKeyKind kind = it->first.kind();
-      switch (kind) {
-        case RasterCacheKeyKind::kPictureMetrics:
-          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;
+      if (entry.unused_count < entry.unused_threshold()) {
+        entry.unused_count++;
+        if (entry.image) {
+          RasterCacheMetrics& metrics = GetMetricsForKind(it->first.kind());
+          metrics.unused_count++;
+          metrics.unused_bytes += entry.image->image_bytes();
+        }
+      } else {
+        dead.push_back(it);
       }
+    } else if (entry.image) {
+      RasterCacheMetrics& metrics = GetMetricsForKind(it->first.kind());
+      metrics.in_use_count++;
+      metrics.in_use_bytes += entry.image->image_bytes();
     }
     entry.used_this_frame = false;
   }
 
   for (auto it : dead) {
     if (it->second.image) {
-      RasterCacheKeyKind kind = it->first.kind();
-      switch (kind) {
-        case RasterCacheKeyKind::kPictureMetrics:
-          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);
   }
 }
 
@@ -447,7 +444,7 @@ void RasterCache::CleanupAfterFrame() {
   layer_metrics_ = {};
   {
     TRACE_EVENT0("flutter", "RasterCache::SweepCaches");
-    SweepOneCacheAfterFrame(cache_, picture_metrics_, layer_metrics_);
+    SweepCacheAfterFrame();
   }
   TraceStatsToTimeline();
 }
@@ -458,6 +455,15 @@ void RasterCache::Clear() {
   layer_metrics_ = {};
 }
 
+RasterCacheMetrics& RasterCache::GetMetricsForKind(RasterCacheKeyKind kind) {
+  switch (kind) {
+    case RasterCacheKeyKind::kPictureMetrics:
+      return picture_metrics_;
+    case RasterCacheKeyKind::kLayerMetrics:
+      return layer_metrics_;
+  }
+}
+
 size_t RasterCache::GetCachedEntriesCount() const {
   return cache_.size();
 }

flow/raster_cache.h

@@ -67,19 +67,32 @@ struct RasterCacheMetrics {
    */
   size_t in_use_bytes = 0;
 
+  /**
+   * The number of cache entries with images unused but kept in this frame.
+   */
+  size_t unused_count = 0;
+
+  /**
+   * The size of all of the images unused but kept in this frame.
+   */
+  size_t unused_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.
    */
-  size_t total_count() const { return in_use_count + eviction_count; }
+  size_t total_count() const {
+    return in_use_count + unused_count + eviction_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.
    */
-  size_t total_bytes() const { return in_use_bytes + eviction_bytes; }
+  size_t total_bytes() const {
+    return in_use_bytes + unused_bytes + eviction_bytes;
+  }
 };
 
 class RasterCache {
@@ -89,6 +102,9 @@ class RasterCache {
   // on that frame. This limit allows us to throttle the cache and distribute
   // the work across multiple frames.
   static constexpr int kDefaultPictureAndDispLayListCacheLimitPerFrame = 3;
+  // The default number of frames the high-priority entry which is high priority
+  // survives if it is not used.
+  static constexpr int kHighPriorityEvictionThreshold = 3;
 
   explicit RasterCache(size_t access_threshold = 3,
                        size_t picture_and_display_list_cache_limit_per_frame =
@@ -186,13 +202,15 @@ class RasterCache {
                bool is_complex,
                bool will_change,
                const SkMatrix& untranslated_matrix,
-               const SkPoint& offset = SkPoint());
+               const SkPoint& offset = SkPoint(),
+               bool is_high_priority = false);
   bool Prepare(PrerollContext* context,
                DisplayList* display_list,
                bool is_complex,
                bool will_change,
                const SkMatrix& untranslated_matrix,
-               const SkPoint& offset = SkPoint());
+               const SkPoint& offset = SkPoint(),
+               bool is_high_priority = false);
 
   // If there is cache entry for this picture, display list or layer, mark it as
   // used for this frame in order to not get evicted. This is needed during
@@ -286,9 +304,18 @@ class RasterCache {
 
  private:
   struct Entry {
+    // If the entry is high priority, it will always cache on first usage and
+    // survive 3 frames without usage.
+    bool is_high_priority = false;
     bool used_this_frame = false;
     size_t access_count = 0;
+    size_t unused_count = 0;
     std::unique_ptr<RasterCacheResult> image;
+    // Return the number of frames the entry survives if it is not used. If the
+    // number is 0, then it will be evicted when not in use.
+    size_t unused_threshold() const {
+      return is_high_priority ? kHighPriorityEvictionThreshold : 0;
+    }
   };
 
   void Touch(const RasterCacheKey& cache_key);
@@ -297,9 +324,9 @@ class RasterCache {
             SkCanvas& canvas,
             const SkPaint* paint) const;
 
-  void SweepOneCacheAfterFrame(RasterCacheKey::Map<Entry>& cache,
-                               RasterCacheMetrics& picture_metrics,
-                               RasterCacheMetrics& layer_metrics);
+  void SweepCacheAfterFrame();
+
+  RasterCacheMetrics& GetMetricsForKind(RasterCacheKeyKind kind);
 
   bool GenerateNewCacheInThisFrame() const {
     // Disabling caching when access_threshold is zero is historic behavior.