cc: Rename ImageDecodeController to ImageDecodeCache.

cc/tiles/gpu_image_decode_controller.h

-// 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.
-
-#ifndef CC_TILES_GPU_IMAGE_DECODE_CONTROLLER_H_
-#define CC_TILES_GPU_IMAGE_DECODE_CONTROLLER_H_
-
-#include <memory>
-#include <unordered_map>
-#include <vector>
-
-#include "base/containers/mru_cache.h"
-#include "base/memory/discardable_memory.h"
-#include "base/memory/memory_coordinator_client.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"
-
-namespace cc {
-
-class ContextProvider;
-
-// OVERVIEW:
-//
-// 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.
-//
-// RASTER-SCALE CACHING:
-//
-// 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 https://goo.gl/0zCd9Z
-//
-// REF COUNTING:
-//
-// 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,
-      public base::MemoryCoordinatorClient {
- public:
-  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;
-
-  // base::MemoryCoordinatorClient overrides.
-  void OnMemoryStateChange(base::MemoryState state) 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 SetCachedBytesLimitForTesting(size_t limit) {
-    cached_bytes_limit_ = limit;
-  }
-  size_t GetBytesUsedForTesting() const { return bytes_used_; }
-  size_t GetNumCacheEntriesForTesting() const {
-    return persistent_cache_.size();
-  }
-  size_t GetDrawImageSizeForTesting(const DrawImage& image);
-  void SetImageDecodingFailedForTesting(const DrawImage& image);
-  bool DiscardableIsLockedForTesting(const DrawImage& image);
-
- private:
-  enum class DecodedDataMode { GPU, CPU };
-
-  // Stores the CPU-side decoded bits of an image and supporting fields.
-  struct DecodedImageData {
-    DecodedImageData();
-    ~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;
-
-   private:
-    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 {
-    UploadedImageData();
-    ~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;
-
-   private:
-    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,
-              const SkImage::DeferredTextureImageUsageParams& upload_params);
-
-    const DecodedDataMode mode;
-    const size_t size;
-    bool is_at_raster = false;
-    SkImage::DeferredTextureImageUsageParams upload_params;
-
-    // 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;
-
-   private:
-    friend class base::RefCounted<ImageData>;
-    ~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);
-    ~InUseCacheEntry();
-
-    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(const DrawImage& draw_image, 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_;
-
-  const size_t normal_max_gpu_image_bytes_;
-  size_t cached_bytes_limit_ = normal_max_gpu_image_bytes_;
-  size_t bytes_used_ = 0;
-  base::MemoryState memory_state_ = base::MemoryState::NORMAL;
-
-  // 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
-
-#endif  // CC_TILES_GPU_IMAGE_DECODE_CONTROLLER_H_