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// Copyright 2016 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#include <memory>
#include <unordered_map>
#include <vector>
#include "base/containers/mru_cache.h"
#include "base/memory/discardable_memory.h"
#include "base/synchronization/lock.h"
#include "base/trace_event/memory_dump_provider.h"
#include "cc/base/cc_export.h"
#include "cc/resources/resource_format.h"
#include "cc/tiles/image_decode_controller.h"
#include "third_party/skia/include/core/SkRefCnt.h"
class SkImageTextureData;
namespace cc {
class ContextProvider;
// GpuImageDecodeController handles the decode and upload of images that will
// be used by Skia's GPU raster path. It also maintains a cache of these
// decoded/uploaded images for later re-use.
// Generally, when an image is required for raster, GpuImageDecodeController
// creates two tasks, one to decode the image, and one to upload the image to
// the GPU. These tasks are completed before the raster task which depends on
// the image. We need to seperate decode and upload tasks, as decode can occur
// simultaneously on multiple threads, while upload requires the GL context
// lock must happen on our non-concurrent raster thread.
// Decoded and Uploaded image data share a single cache entry. Depending on how
// far we've progressed, this cache entry may contain CPU-side decoded data,
// GPU-side uploaded data, or both. Because CPU-side decoded data is stored in
// discardable memory, and is only locked for short periods of time (until the
// upload completes), this memory is not counted against our sized cache
// limits. Uploaded GPU memory, being non-discardable, always counts against
// our limits.
// In cases where the number of images needed exceeds our cache limits, we
// operate in an "at-raster" mode. In this mode, there are no decode/upload
// tasks, and images are decoded/uploaded as needed, immediately before being
// used in raster. Cache entries for at-raster tasks are marked as such, which
// prevents future tasks from taking a dependency on them and extending their
// lifetime longer than is necessary.
// In order to save memory, images which are going to be scaled may be uploaded
// at lower than original resolution. In these cases, we may later need to
// re-upload the image at a higher resolution. To handle multiple images of
// different scales being in use at the same time, we have a two-part caching
// system.
// The first cache, |persistent_cache_|, stores one ImageData per image id.
// These ImageDatas are not necessarily associated with a given DrawImage, and
// are saved (persisted) even when their ref-count reaches zero (assuming they
// fit in the current memory budget). This allows for future re-use of image
// resources.
// The second cache, |in_use_cache_|, stores one image data per DrawImage -
// this may be the same ImageData that is in the persistent_cache_. These
// cache entries are more transient and are deleted as soon as all refs to the
// given DrawImage are released (the image is no longer in-use).
// For examples of raster-scale caching, see
// In dealing with the two caches in GpuImageDecodeController, there are three
// ref-counting concepts in use:
// 1) ImageData upload/decode ref-counts.
// These ref-counts represent the overall number of references to the
// upload or decode portion of an ImageData. These ref-counts control
// both whether the upload/decode data can be freed, as well as whether an
// ImageData can be removed from the |persistent_cache_|. ImageDatas are
// only removed from the |persistent_cache_| if their upload/decode
// ref-counts are zero or if they are orphaned and replaced by a new entry.
// 2) InUseCacheEntry ref-counts.
// These ref-counts represent the number of references to an
// InUseCacheEntry from a specific DrawImage. When the InUseCacheEntry's
// ref-count reaches 0 it will be deleted.
// 3) scoped_refptr ref-counts.
// Because both the persistent_cache_ and the in_use_cache_ point at the
// same ImageDatas (and may need to keep these ImageDatas alive independent
// of each other), they hold ImageDatas by scoped_refptr. The scoped_refptr
// keeps an ImageData alive while it is present in either the
// |persistent_cache_| or |in_use_cache_|.
class CC_EXPORT GpuImageDecodeController
: public ImageDecodeController,
public base::trace_event::MemoryDumpProvider {
explicit GpuImageDecodeController(ContextProvider* context,
ResourceFormat decode_format,
size_t max_gpu_image_bytes);
~GpuImageDecodeController() override;
// ImageDecodeController overrides.
// Finds the existing uploaded image for the provided DrawImage. Creates an
// upload task to upload the image if an exsiting image does not exist.
bool GetTaskForImageAndRef(const DrawImage& image,
const TracingInfo& tracing_info,
scoped_refptr<TileTask>* task) override;
void UnrefImage(const DrawImage& image) override;
DecodedDrawImage GetDecodedImageForDraw(const DrawImage& draw_image) override;
void DrawWithImageFinished(const DrawImage& image,
const DecodedDrawImage& decoded_image) override;
void ReduceCacheUsage() override;
void SetShouldAggressivelyFreeResources(
bool aggressively_free_resources) override;
// MemoryDumpProvider overrides.
bool OnMemoryDump(const base::trace_event::MemoryDumpArgs& args,
base::trace_event::ProcessMemoryDump* pmd) override;
// Called by Decode / Upload tasks.
void DecodeImage(const DrawImage& image);
void UploadImage(const DrawImage& image);
// Called by Decode / Upload tasks when tasks are finished.
void OnImageDecodeTaskCompleted(const DrawImage& image);
void OnImageUploadTaskCompleted(const DrawImage& image);
// For testing only.
void SetCachedItemLimitForTesting(size_t limit) {
cached_items_limit_ = limit;
void SetCachedBytesLimitForTesting(size_t limit) {
cached_bytes_limit_ = limit;
size_t GetBytesUsedForTesting() const { return bytes_used_; }
size_t GetDrawImageSizeForTesting(const DrawImage& image);
void SetImageDecodingFailedForTesting(const DrawImage& image);
bool DiscardableIsLockedForTesting(const DrawImage& image);
enum class DecodedDataMode { GPU, CPU };
// Stores the CPU-side decoded bits of an image and supporting fields.
struct DecodedImageData {
bool is_locked() const { return is_locked_; }
bool Lock();
void Unlock();
void SetLockedData(std::unique_ptr<base::DiscardableMemory> data);
void ResetData();
base::DiscardableMemory* data() const { return data_.get(); }
void mark_used() { usage_stats_.used = true; }
uint32_t ref_count = 0;
// Set to true if the image was corrupt and could not be decoded.
bool decode_failure = false;
// If non-null, this is the pending decode task for this image.
scoped_refptr<TileTask> task;
struct UsageStats {
int lock_count = 1;
bool used = false;
bool first_lock_wasted = false;
void ReportUsageStats() const;
std::unique_ptr<base::DiscardableMemory> data_;
bool is_locked_ = false;
UsageStats usage_stats_;
// Stores the GPU-side image and supporting fields.
struct UploadedImageData {
void SetImage(sk_sp<SkImage> image);
const sk_sp<SkImage>& image() const { return image_; }
void mark_used() { usage_stats_.used = true; }
void notify_ref_reached_zero() {
if (++usage_stats_.ref_reached_zero_count == 1)
usage_stats_.first_ref_wasted = !usage_stats_.used;
// True if the image is counting against our memory limits.
bool budgeted = false;
uint32_t ref_count = 0;
// If non-null, this is the pending upload task for this image.
scoped_refptr<TileTask> task;
struct UsageStats {
bool used = false;
bool first_ref_wasted = false;
int ref_reached_zero_count = 0;
void ReportUsageStats() const;
// May be null if image not yet uploaded / prepared.
sk_sp<SkImage> image_;
UsageStats usage_stats_;
struct ImageData : public base::RefCounted<ImageData> {
ImageData(DecodedDataMode mode,
size_t size,
int upload_scale_mip_level,
SkFilterQuality upload_scale_filter_quality);
const DecodedDataMode mode;
const size_t size;
bool is_at_raster = false;
// Variables used to identify/track multiple scale levels of a single image.
int upload_scale_mip_level = 0;
SkFilterQuality upload_scale_filter_quality = kNone_SkFilterQuality;
// If true, this image is no longer in our |persistent_cache_| and will be
// deleted as soon as its ref count reaches zero.
bool is_orphaned = false;
DecodedImageData decode;
UploadedImageData upload;
friend class base::RefCounted<ImageData>;
// A ref-count and ImageData, used to associate the ImageData with a specific
// DrawImage in the |in_use_cache_|.
struct InUseCacheEntry {
explicit InUseCacheEntry(scoped_refptr<ImageData> image_data);
InUseCacheEntry(const InUseCacheEntry& other);
InUseCacheEntry(InUseCacheEntry&& other);
uint32_t ref_count = 0;
scoped_refptr<ImageData> image_data;
// Uniquely identifies (without collisions) a specific DrawImage for use in
// the |in_use_cache_|.
using InUseCacheKey = uint64_t;
// All private functions should only be called while holding |lock_|. Some
// functions also require the |context_| lock. These are indicated by
// additional comments.
// Similar to GetTaskForImageAndRef, but gets the dependent decode task
// rather than the upload task, if necessary.
scoped_refptr<TileTask> GetImageDecodeTaskAndRef(
const DrawImage& image,
const TracingInfo& tracing_info);
void RefImageDecode(const DrawImage& draw_image);
void UnrefImageDecode(const DrawImage& draw_image);
void RefImage(const DrawImage& draw_image);
void UnrefImageInternal(const DrawImage& draw_image);
// Called any time the ownership of an object changed. This includes changes
// to ref-count or to orphaned status.
void OwnershipChanged(ImageData* image_data);
// Ensures that the cache can hold an element of |required_size|, freeing
// unreferenced cache entries if necessary to make room.
bool EnsureCapacity(size_t required_size);
bool CanFitSize(size_t size) const;
bool ExceedsPreferredCount() const;
void DecodeImageIfNecessary(const DrawImage& draw_image,
ImageData* image_data);
scoped_refptr<GpuImageDecodeController::ImageData> CreateImageData(
const DrawImage& image);
SkImageInfo CreateImageInfoForDrawImage(const DrawImage& draw_image,
int upload_scale_mip_level) const;
// Finds the ImageData that should be used for the given DrawImage. Looks
// first in the |in_use_cache_|, and then in the |persistent_cache_|.
ImageData* GetImageDataForDrawImage(const DrawImage& image);
// Returns true if the given ImageData can be used to draw the specified
// DrawImage.
bool IsCompatible(const ImageData* image_data,
const DrawImage& draw_image) const;
// The following two functions also require the |context_| lock to be held.
void UploadImageIfNecessary(const DrawImage& draw_image,
ImageData* image_data);
void DeletePendingImages();
const ResourceFormat format_;
ContextProvider* context_;
sk_sp<GrContextThreadSafeProxy> context_threadsafe_proxy_;
// All members below this point must only be accessed while holding |lock_|.
base::Lock lock_;
// |persistent_cache_| represents the long-lived cache, keeping a certain
// budget of ImageDatas alive even when their ref count reaches zero.
using PersistentCache = base::MRUCache<uint32_t, scoped_refptr<ImageData>>;
PersistentCache persistent_cache_;
// |in_use_cache_| represents the in-use (short-lived) cache. Entries are
// cleaned up as soon as their ref count reaches zero.
using InUseCache = std::unordered_map<InUseCacheKey, InUseCacheEntry>;
InUseCache in_use_cache_;
size_t cached_items_limit_;
size_t cached_bytes_limit_;
size_t bytes_used_;
const size_t max_gpu_image_bytes_;
// We can't release GPU backed SkImages without holding the context lock,
// so we add them to this list and defer deletion until the next time the lock
// is held.
std::vector<sk_sp<SkImage>> images_pending_deletion_;
} // namespace cc