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* 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/SkSpinlock.h"
#include "src/core/SkArenaAlloc.h"
#include "src/core/SkTDynamicHash.h"
#include "src/core/SkTInternalLList.h"
#include "src/gpu/GrSurfaceProxyView.h"
class GrGpuBuffer;
// 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 {
int numEntries() const SK_EXCLUDES(fSpinLock);
size_t approxBytesUsedForHash() const SK_EXCLUDES(fSpinLock);
void dropAllRefs() SK_EXCLUDES(fSpinLock);
// Drop uniquely held refs until under the resource cache's budget.
// A null parameter means drop all uniquely held refs.
void dropUniqueRefs(GrResourceCache* resourceCache) SK_EXCLUDES(fSpinLock);
// Drop uniquely held refs that were last accessed before 'purgeTime'
void dropUniqueRefsOlderThan(GrStdSteadyClock::time_point purgeTime) SK_EXCLUDES(fSpinLock);
SkDEBUGCODE(bool has(const GrUniqueKey&) SK_EXCLUDES(fSpinLock);)
GrSurfaceProxyView find(const GrUniqueKey&) SK_EXCLUDES(fSpinLock);
std::tuple<GrSurfaceProxyView, sk_sp<SkData>> findWithData(
const GrUniqueKey&) SK_EXCLUDES(fSpinLock);
GrSurfaceProxyView add(const GrUniqueKey&, const GrSurfaceProxyView&) SK_EXCLUDES(fSpinLock);
std::tuple<GrSurfaceProxyView, sk_sp<SkData>> addWithData(
const GrUniqueKey&, const GrSurfaceProxyView&) SK_EXCLUDES(fSpinLock);
GrSurfaceProxyView findOrAdd(const GrUniqueKey&,
const GrSurfaceProxyView&) SK_EXCLUDES(fSpinLock);
std::tuple<GrSurfaceProxyView, sk_sp<SkData>> findOrAddWithData(
const GrUniqueKey&, const GrSurfaceProxyView&) SK_EXCLUDES(fSpinLock);
// To hold vertex data in the cache and have it transparently transition from cpu-side to
// gpu-side while being shared between all the threads we need a ref counted object that
// keeps hold of the cpu-side data but allows deferred filling in of the mirroring gpu buffer.
class VertexData : public SkNVRefCnt<VertexData> {
const void* vertices() const { return fVertices; }
size_t size() const { return fNumVertices * fVertexSize; }
int numVertices() const { return fNumVertices; }
size_t vertexSize() const { return fVertexSize; }
// TODO: make these return const GrGpuBuffers?
GrGpuBuffer* gpuBuffer() { return fGpuBuffer.get(); }
sk_sp<GrGpuBuffer> refGpuBuffer() { return fGpuBuffer; }
void setGpuBuffer(sk_sp<GrGpuBuffer> gpuBuffer) {
// TODO: once we add the gpuBuffer we could free 'fVertices'. Deinstantiable
// DDLs could throw a monkey wrench into that plan though.
fGpuBuffer = gpuBuffer;
void reset() {
fVertices = nullptr;
fNumVertices = 0;
fVertexSize = 0;
friend class GrThreadSafeCache; // for access to ctor
VertexData(const void* vertices, int numVertices, size_t vertexSize)
: fVertices(vertices)
, fNumVertices(numVertices)
, fVertexSize(vertexSize) {
VertexData(sk_sp<GrGpuBuffer> gpuBuffer, int numVertices, size_t vertexSize)
: fVertices(nullptr)
, fNumVertices(numVertices)
, fVertexSize(vertexSize)
, fGpuBuffer(std::move(gpuBuffer)) {
const void* fVertices;
int fNumVertices;
size_t fVertexSize;
sk_sp<GrGpuBuffer> fGpuBuffer;
// The returned VertexData object takes ownership of 'vertices' which had better have been
// allocated with malloc!
static sk_sp<VertexData> MakeVertexData(const void* vertices,
int vertexCount,
size_t vertexSize);
static sk_sp<VertexData> MakeVertexData(sk_sp<GrGpuBuffer> buffer,
int vertexCount,
size_t vertexSize);
std::tuple<sk_sp<VertexData>, sk_sp<SkData>> findVertsWithData(
const GrUniqueKey&) SK_EXCLUDES(fSpinLock);
typedef bool (*IsNewerBetter)(SkData* incumbent, SkData* challenger);
std::tuple<sk_sp<VertexData>, sk_sp<SkData>> addVertsWithData(
const GrUniqueKey&,
IsNewerBetter) SK_EXCLUDES(fSpinLock);
void remove(const GrUniqueKey&) SK_EXCLUDES(fSpinLock);
// To allow gpu-created resources to have priority, we pre-emptively place a lazy proxy
// in the thread-safe cache (with findOrAdd). The Trampoline object allows that lazy proxy to
// be instantiated with some later generated rendering result.
class Trampoline : public SkRefCnt {
sk_sp<GrTextureProxy> fProxy;
static std::tuple<GrSurfaceProxyView, sk_sp<Trampoline>> CreateLazyView(GrDirectContext*,
SkISize dimensions,
struct Entry {
Entry(const GrUniqueKey& key, const GrSurfaceProxyView& view)
: fKey(key)
, fView(view)
, fTag(Entry::kView) {
Entry(const GrUniqueKey& key, sk_sp<VertexData> vertData)
: fKey(key)
, fVertData(std::move(vertData))
, fTag(Entry::kVertData) {
~Entry() {
bool uniquelyHeld() const {
SkASSERT(fTag != kEmpty);
if (fTag == kView && fView.proxy()->unique()) {
return true;
} else if (fTag == kVertData && fVertData->unique()) {
return true;
return false;
const GrUniqueKey& key() const {
SkASSERT(fTag != kEmpty);
return fKey;
SkData* getCustomData() const {
SkASSERT(fTag != kEmpty);
return fKey.getCustomData();
sk_sp<SkData> refCustomData() const {
SkASSERT(fTag != kEmpty);
return fKey.refCustomData();
GrSurfaceProxyView view() {
SkASSERT(fTag == kView);
return fView;
sk_sp<VertexData> vertexData() {
SkASSERT(fTag == kVertData);
return fVertData;
void set(const GrUniqueKey& key, const GrSurfaceProxyView& view) {
SkASSERT(fTag == kEmpty);
fKey = key;
fView = view;
fTag = kView;
void makeEmpty() {
if (fTag == kView) {
} else if (fTag == kVertData) {
fTag = kEmpty;
void set(const GrUniqueKey& key, sk_sp<VertexData> vertData) {
SkASSERT(fTag == kEmpty || fTag == kVertData);
fKey = key;
fVertData = vertData;
fTag = kVertData;
// The thread-safe cache gets to directly manipulate the llist and last-access members
GrStdSteadyClock::time_point fLastAccess;
// for SkTDynamicHash
static const GrUniqueKey& GetKey(const Entry& e) {
SkASSERT(e.fTag != kEmpty);
return e.fKey;
static uint32_t Hash(const GrUniqueKey& key) { return key.hash(); }
// Note: the unique key is stored here bc it is never attached to a proxy or a GrTexture
GrUniqueKey fKey;
union {
GrSurfaceProxyView fView;
sk_sp<VertexData> fVertData;
enum {
} fTag { kEmpty };
void makeExistingEntryMRU(Entry*) SK_REQUIRES(fSpinLock);
Entry* makeNewEntryMRU(Entry*) SK_REQUIRES(fSpinLock);
Entry* getEntry(const GrUniqueKey&, const GrSurfaceProxyView&) SK_REQUIRES(fSpinLock);
Entry* getEntry(const GrUniqueKey&, sk_sp<VertexData>) SK_REQUIRES(fSpinLock);
void recycleEntry(Entry*) SK_REQUIRES(fSpinLock);
std::tuple<GrSurfaceProxyView, sk_sp<SkData>> internalFind(
const GrUniqueKey&) SK_REQUIRES(fSpinLock);
std::tuple<GrSurfaceProxyView, sk_sp<SkData>> internalAdd(
const GrUniqueKey&,
const GrSurfaceProxyView&) SK_REQUIRES(fSpinLock);
std::tuple<sk_sp<VertexData>, sk_sp<SkData>> internalFindVerts(
const GrUniqueKey&) SK_REQUIRES(fSpinLock);
std::tuple<sk_sp<VertexData>, sk_sp<SkData>> internalAddVerts(
const GrUniqueKey&,
IsNewerBetter) SK_REQUIRES(fSpinLock);
mutable SkSpinlock fSpinLock;
SkTDynamicHash<Entry, GrUniqueKey> fUniquelyKeyedEntryMap SK_GUARDED_BY(fSpinLock);
// The head of this list is the MRU
SkTInternalLList<Entry> fUniquelyKeyedEntryList SK_GUARDED_BY(fSpinLock);
// TODO: empirically determine this from the skps
static const int kInitialArenaSize = 64 * sizeof(Entry);
char fStorage[kInitialArenaSize];
SkArenaAlloc fEntryAllocator{fStorage, kInitialArenaSize, kInitialArenaSize};
Entry* fFreeEntryList SK_GUARDED_BY(fSpinLock);
#endif // GrThreadSafeCache_DEFINED