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/*
* Copyright 2013 Google Inc.
*
* Use of this source code is governed by a BSD-style license that can be
* found in the LICENSE file.
*/
#include "SkDiscardableMemoryPool.h"
#include "SkDiscardableMemory.h"
#include "SkMakeUnique.h"
#include "SkMalloc.h"
#include "SkMutex.h"
#include "SkTInternalLList.h"
#include "SkTemplates.h"
// Note:
// A PoolDiscardableMemory is memory that is counted in a pool.
// A DiscardableMemoryPool is a pool of PoolDiscardableMemorys.
namespace {
class PoolDiscardableMemory;
/**
* This non-global pool can be used for unit tests to verify that the
* pool works.
*/
class DiscardableMemoryPool : public SkDiscardableMemoryPool {
public:
DiscardableMemoryPool(size_t budget);
~DiscardableMemoryPool() override;
std::unique_ptr<SkDiscardableMemory> make(size_t bytes);
SkDiscardableMemory* create(size_t bytes) override {
return this->make(bytes).release(); // TODO: change API
}
size_t getRAMUsed() override;
void setRAMBudget(size_t budget) override;
size_t getRAMBudget() override { return fBudget; }
/** purges all unlocked DMs */
void dumpPool() override;
#if SK_LAZY_CACHE_STATS // Defined in SkDiscardableMemoryPool.h
int getCacheHits() override { return fCacheHits; }
int getCacheMisses() override { return fCacheMisses; }
void resetCacheHitsAndMisses() override {
fCacheHits = fCacheMisses = 0;
}
int fCacheHits;
int fCacheMisses;
#endif // SK_LAZY_CACHE_STATS
private:
SkMutex fMutex;
size_t fBudget;
size_t fUsed;
SkTInternalLList<PoolDiscardableMemory> fList;
/** Function called to free memory if needed */
void dumpDownTo(size_t budget);
/** called by DiscardableMemoryPool upon destruction */
void removeFromPool(PoolDiscardableMemory* dm);
/** called by DiscardableMemoryPool::lock() */
bool lock(PoolDiscardableMemory* dm);
/** called by DiscardableMemoryPool::unlock() */
void unlock(PoolDiscardableMemory* dm);
friend class PoolDiscardableMemory;
typedef SkDiscardableMemory::Factory INHERITED;
};
/**
* A PoolDiscardableMemory is a SkDiscardableMemory that relies on
* a DiscardableMemoryPool object to manage the memory.
*/
class PoolDiscardableMemory : public SkDiscardableMemory {
public:
PoolDiscardableMemory(sk_sp<DiscardableMemoryPool> pool, SkAutoFree pointer, size_t bytes);
~PoolDiscardableMemory() override;
bool lock() override;
void* data() override;
void unlock() override;
friend class DiscardableMemoryPool;
private:
SK_DECLARE_INTERNAL_LLIST_INTERFACE(PoolDiscardableMemory);
sk_sp<DiscardableMemoryPool> fPool;
bool fLocked;
SkAutoFree fPointer;
const size_t fBytes;
};
PoolDiscardableMemory::PoolDiscardableMemory(sk_sp<DiscardableMemoryPool> pool,
SkAutoFree pointer,
size_t bytes)
: fPool(std::move(pool)), fLocked(true), fPointer(std::move(pointer)), fBytes(bytes) {
SkASSERT(fPool != nullptr);
SkASSERT(fPointer != nullptr);
SkASSERT(fBytes > 0);
}
PoolDiscardableMemory::~PoolDiscardableMemory() {
SkASSERT(!fLocked); // contract for SkDiscardableMemory
fPool->removeFromPool(this);
}
bool PoolDiscardableMemory::lock() {
SkASSERT(!fLocked); // contract for SkDiscardableMemory
return fPool->lock(this);
}
void* PoolDiscardableMemory::data() {
SkASSERT(fLocked); // contract for SkDiscardableMemory
return fPointer.get();
}
void PoolDiscardableMemory::unlock() {
SkASSERT(fLocked); // contract for SkDiscardableMemory
fPool->unlock(this);
}
////////////////////////////////////////////////////////////////////////////////
DiscardableMemoryPool::DiscardableMemoryPool(size_t budget)
: fBudget(budget)
, fUsed(0) {
#if SK_LAZY_CACHE_STATS
fCacheHits = 0;
fCacheMisses = 0;
#endif // SK_LAZY_CACHE_STATS
}
DiscardableMemoryPool::~DiscardableMemoryPool() {
// PoolDiscardableMemory objects that belong to this pool are
// always deleted before deleting this pool since each one has a
// ref to the pool.
SkASSERT(fList.isEmpty());
}
void DiscardableMemoryPool::dumpDownTo(size_t budget) {
fMutex.assertHeld();
if (fUsed <= budget) {
return;
}
using Iter = SkTInternalLList<PoolDiscardableMemory>::Iter;
Iter iter;
PoolDiscardableMemory* cur = iter.init(fList, Iter::kTail_IterStart);
while ((fUsed > budget) && (cur)) {
if (!cur->fLocked) {
PoolDiscardableMemory* dm = cur;
SkASSERT(dm->fPointer != nullptr);
dm->fPointer = nullptr;
SkASSERT(fUsed >= dm->fBytes);
fUsed -= dm->fBytes;
cur = iter.prev();
// Purged DMs are taken out of the list. This saves times
// looking them up. Purged DMs are NOT deleted.
fList.remove(dm);
} else {
cur = iter.prev();
}
}
}
std::unique_ptr<SkDiscardableMemory> DiscardableMemoryPool::make(size_t bytes) {
SkAutoFree addr(sk_malloc_flags(bytes, 0));
if (nullptr == addr) {
return nullptr;
}
auto dm = skstd::make_unique<PoolDiscardableMemory>(sk_ref_sp(this), std::move(addr), bytes);
SkAutoMutexAcquire autoMutexAcquire(fMutex);
fList.addToHead(dm.get());
fUsed += bytes;
this->dumpDownTo(fBudget);
return std::move(dm);
}
void DiscardableMemoryPool::removeFromPool(PoolDiscardableMemory* dm) {
SkAutoMutexAcquire autoMutexAcquire(fMutex);
// This is called by dm's destructor.
if (dm->fPointer != nullptr) {
SkASSERT(fUsed >= dm->fBytes);
fUsed -= dm->fBytes;
fList.remove(dm);
} else {
SkASSERT(!fList.isInList(dm));
}
}
bool DiscardableMemoryPool::lock(PoolDiscardableMemory* dm) {
SkASSERT(dm != nullptr);
SkAutoMutexAcquire autoMutexAcquire(fMutex);
if (nullptr == dm->fPointer) {
// May have been purged while waiting for lock.
#if SK_LAZY_CACHE_STATS
++fCacheMisses;
#endif // SK_LAZY_CACHE_STATS
return false;
}
dm->fLocked = true;
fList.remove(dm);
fList.addToHead(dm);
#if SK_LAZY_CACHE_STATS
++fCacheHits;
#endif // SK_LAZY_CACHE_STATS
return true;
}
void DiscardableMemoryPool::unlock(PoolDiscardableMemory* dm) {
SkASSERT(dm != nullptr);
SkAutoMutexAcquire autoMutexAcquire(fMutex);
dm->fLocked = false;
this->dumpDownTo(fBudget);
}
size_t DiscardableMemoryPool::getRAMUsed() {
return fUsed;
}
void DiscardableMemoryPool::setRAMBudget(size_t budget) {
SkAutoMutexAcquire autoMutexAcquire(fMutex);
fBudget = budget;
this->dumpDownTo(fBudget);
}
void DiscardableMemoryPool::dumpPool() {
SkAutoMutexAcquire autoMutexAcquire(fMutex);
this->dumpDownTo(0);
}
} // namespace
sk_sp<SkDiscardableMemoryPool> SkDiscardableMemoryPool::Make(size_t size) {
return sk_make_sp<DiscardableMemoryPool>(size);
}
SkDiscardableMemoryPool* SkGetGlobalDiscardableMemoryPool() {
// Intentionally leak this global pool.
static SkDiscardableMemoryPool* global =
new DiscardableMemoryPool(SK_DEFAULT_GLOBAL_DISCARDABLE_MEMORY_POOL_SIZE);
return global;
}
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