chromium/third_party/skia/src/gpu/ganesh/GrThreadSafeCache.h

/*
 * Copyright 2020 Google Inc.
 *
 * Use of this source code is governed by a BSD-style license that can be
 * found in the LICENSE file.
 */

#ifndef GrThreadSafeCache_DEFINED
#define GrThreadSafeCache_DEFINED

#include "include/core/SkRefCnt.h"
#include "include/private/base/SkAssert.h"
#include "include/private/base/SkDebug.h"
#include "include/private/base/SkMalloc.h"
#include "include/private/base/SkThreadAnnotations.h"
#include "src/base/SkArenaAlloc.h"
#include "src/base/SkSpinlock.h"
#include "src/base/SkTInternalLList.h"
#include "src/core/SkTDynamicHash.h"
#include "src/gpu/GpuTypesPriv.h"
#include "src/gpu/ResourceKey.h"
#include "src/gpu/ganesh/GrGpuBuffer.h"
#include "src/gpu/ganesh/GrSurfaceProxy.h"
#include "src/gpu/ganesh/GrSurfaceProxyView.h"
#include "src/gpu/ganesh/GrTextureProxy.h"

#include <cstddef>
#include <cstdint>
#include <tuple>
#include <utility>

class GrDirectContext;
class GrResourceCache;
class SkData;
enum GrSurfaceOrigin : int;
enum class GrColorType;
enum class SkBackingFit;
struct SkISize;

// Ganesh creates a lot of utility textures (e.g., blurred-rrect masks) that need to be shared
// between the direct context and all the DDL recording contexts. This thread-safe cache
// allows this sharing.
//
// In operation, each thread will first check if the threaded cache possesses the required texture.
//
// If a DDL thread doesn't find a needed texture it will go off and create it on the cpu and then
// attempt to add it to the cache. If another thread had added it in the interim, the losing thread
// will discard its work and use the texture the winning thread had created.
//
// If the thread in possession of the direct context doesn't find the needed texture it should
// add a place holder view and then queue up the draw calls to complete it. In this way the
// gpu-thread has precedence over the recording threads.
//
// The invariants for this cache differ a bit from those of the proxy and resource caches.
// For this cache:
//
//   only this cache knows the unique key - neither the proxy nor backing resource should
//              be discoverable in any other cache by the unique key
//   if a backing resource resides in the resource cache then there should be an entry in this
//              cache
//   an entry in this cache, however, doesn't guarantee that there is a corresponding entry in
//              the resource cache - although the entry here should be able to generate that entry
//              (i.e., be a lazy proxy)
//
// Wrt interactions w/ GrContext/GrResourceCache purging, we have:
//
//    Both GrContext::abandonContext and GrContext::releaseResourcesAndAbandonContext will cause
//    all the refs held in this cache to be dropped prior to clearing out the resource cache.
//
//    For the size_t-variant of GrContext::purgeUnlockedResources, after an initial attempt
//    to purge the requested amount of resources fails, uniquely held resources in this cache
//    will be dropped in LRU to MRU order until the cache is under budget. Note that this
//    prioritizes the survival of resources in this cache over those just in the resource cache.
//
//    For the 'scratchResourcesOnly' variant of GrContext::purgeUnlockedResources, this cache
//    won't be modified in the scratch-only case unless the resource cache is over budget (in
//    which case it will purge uniquely-held resources in LRU to MRU order to get
//    back under budget). In the non-scratch-only case, all uniquely held resources in this cache
//    will be released prior to the resource cache being cleared out.
//
//    For GrContext::setResourceCacheLimit, if an initial pass through the resource cache doesn't
//    reach the budget, uniquely held resources in this cache will be released in LRU to MRU order.
//
//    For GrContext::performDeferredCleanup, any uniquely held resources that haven't been accessed
//    w/in 'msNotUsed' will be released from this cache prior to the resource cache being cleaned.
class GrThreadSafeCache { … };

#endif // GrThreadSafeCache_DEFINED