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Generate layer unique id for raster cache key #8637

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liyuqian merged 4 commits into from
Apr 18, 2019
Merged

Generate layer unique id for raster cache key #8637

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371a1fc
Generate layer unique id for raster cache key
liyuqian Apr 18, 2019
b1f7cf4
Clang-format
liyuqian Apr 18, 2019
c2cabfa
Change to uint64_t
liyuqian Apr 18, 2019
7d50236
Remove extra blank line
liyuqian Apr 18, 2019
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12 changes: 11 additions & 1 deletion flow/layers/layer.cc
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Original file line number Diff line number Diff line change
Expand Up @@ -12,10 +12,20 @@ namespace flutter {
Layer::Layer()
: parent_(nullptr),
needs_system_composite_(false),
paint_bounds_(SkRect::MakeEmpty()) {}
paint_bounds_(SkRect::MakeEmpty()),
unique_id_(NextUniqueID()) {}

Layer::~Layer() = default;

uint32_t Layer::NextUniqueID() {

@zanderso zanderso Apr 18, 2019

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What is the rate that these ids are generated at, and how long are these objects expected to live?

@liyuqian liyuqian Apr 18, 2019

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Usually a few (mostly fewer than 10, I never see more than 100) per frame. So that's about 100-200 at full 60fps animations, and I've never seen more than 1000 per second.

A layer may live for a very long time if the scene doesn't change at all. But I'd never expect to have many layers alive at one time. I think it's safe to say that most of the time, no more than 100 are alive at the same time. In extreme cases, maybe never more than 1000 at a time (otherwise compositing all those layers will be very janky).

If we take 1000 layers/second as the generation speed, it'll take 49 days to cycle the unique id.

If we take that no more than 1000 layers are alive at a time, the chance of collision (given that we've cycled the unique id after 49 days, and those 1000 layers live forever) is less than 2^-20 per layer and less than 2^-10 (0.1%) per second.

If that doesn't sound safe enough, I'm happy to use uint64_t for the id.

@zanderso zanderso Apr 18, 2019

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If it's not hard to switch to uint64_t, then let's switch.

@liyuqian liyuqian Apr 18, 2019

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Done.

static std::atomic<uint32_t> nextID(1);
uint32_t id;
do {
id = nextID.fetch_add(1);
} while (id == 0); // 0 is reserved for an invalid id.
return id;
}

void Layer::Preroll(PrerollContext* context, const SkMatrix& matrix) {}

#if defined(OS_FUCHSIA)
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5 changes: 5 additions & 0 deletions flow/layers/layer.h
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Original file line number Diff line number Diff line change
Expand Up @@ -143,10 +143,15 @@ class Layer {

bool needs_painting() const { return !paint_bounds_.isEmpty(); }

uint32_t unique_id() const { return unique_id_; }

private:
ContainerLayer* parent_;
bool needs_system_composite_;
SkRect paint_bounds_;
uint32_t unique_id_;

static uint32_t NextUniqueID();

FML_DISALLOW_COPY_AND_ASSIGN(Layer);
};
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2 changes: 1 addition & 1 deletion flow/layers/physical_shape_layer.cc
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Expand Up @@ -109,7 +109,7 @@ void PhysicalShapeLayer::UpdateScene(SceneUpdateContext& context) {
// Retained rendering: speedup by reusing a retained entity node if possible.
// When an entity node is reused, no paint layer is added to the frame so we
// won't call PhysicalShapeLayer::Paint.
LayerRasterCacheKey key(this, context.Matrix());
LayerRasterCacheKey key(unique_id(), context.Matrix());
if (context.HasRetainedNode(key)) {
const scenic::EntityNode& retained_node = context.GetRetainedNode(key);
FML_DCHECK(context.top_entity());
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4 changes: 2 additions & 2 deletions flow/raster_cache.cc
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Expand Up @@ -151,7 +151,7 @@ static inline size_t ClampSize(size_t value, size_t min, size_t max) {
void RasterCache::Prepare(PrerollContext* context,
Layer* layer,
const SkMatrix& ctm) {
LayerRasterCacheKey cache_key(layer, ctm);
LayerRasterCacheKey cache_key(layer->unique_id(), ctm);
Entry& entry = layer_cache_[cache_key];
entry.access_count = ClampSize(entry.access_count + 1, 0, access_threshold_);
entry.used_this_frame = true;
Expand Down Expand Up @@ -230,7 +230,7 @@ RasterCacheResult RasterCache::Get(const SkPicture& picture,
}

RasterCacheResult RasterCache::Get(Layer* layer, const SkMatrix& ctm) const {
LayerRasterCacheKey cache_key(layer, ctm);
LayerRasterCacheKey cache_key(layer->unique_id(), ctm);
auto it = layer_cache_.find(cache_key);
return it == layer_cache_.end() ? RasterCacheResult() : it->second.image;
}
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3 changes: 2 additions & 1 deletion flow/raster_cache_key.h
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Original file line number Diff line number Diff line change
Expand Up @@ -56,7 +56,8 @@ using PictureRasterCacheKey = RasterCacheKey<uint32_t>;

class Layer;

using LayerRasterCacheKey = RasterCacheKey<Layer*>;
// The ID is the uint32_t layer unique_id
using LayerRasterCacheKey = RasterCacheKey<uint32_t>;

} // namespace flutter

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10 changes: 7 additions & 3 deletions flow/scene_update_context.cc
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Expand Up @@ -163,10 +163,14 @@ scenic::Image* SceneUpdateContext::GenerateImageIfNeeded(
return nullptr;

// Acquire a surface from the surface producer and register the paint tasks.

std::unique_ptr<SurfaceProducerSurface> surface =
surface_producer_->ProduceSurface(physical_size,
LayerRasterCacheKey(layer, Matrix()),
std::move(entity_node));
surface_producer_->ProduceSurface(
physical_size,
LayerRasterCacheKey(
// Root frame has a nullptr layer
layer ? layer->unique_id() : 0, Matrix()),
std::move(entity_node));

if (!surface) {
FML_LOG(ERROR) << "Could not acquire a surface from the surface producer "
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