1 /*
2 * Copyright 2013 Google Inc.
3 *
4 * Use of this source code is governed by a BSD-style license that can be
5 * found in the LICENSE file.
6 */
7
8 #include "SkDiscardableMemoryPool.h"
9 #include "SkOnce.h"
10
11 // Note:
12 // A PoolDiscardableMemory is memory that is counted in a pool.
13 // A DiscardableMemoryPool is a pool of PoolDiscardableMemorys.
14
15 /**
16 * A SkPoolDiscardableMemory is a SkDiscardableMemory that relies on
17 * a SkDiscardableMemoryPool object to manage the memory.
18 */
19 class SkPoolDiscardableMemory : public SkDiscardableMemory {
20 public:
21 SkPoolDiscardableMemory(SkDiscardableMemoryPool* pool,
22 void* pointer, size_t bytes);
23 virtual ~SkPoolDiscardableMemory();
24 virtual bool lock() SK_OVERRIDE;
25 virtual void* data() SK_OVERRIDE;
26 virtual void unlock() SK_OVERRIDE;
27 friend class SkDiscardableMemoryPool;
28 private:
29 SK_DECLARE_INTERNAL_LLIST_INTERFACE(SkPoolDiscardableMemory);
30 SkDiscardableMemoryPool* const fPool;
31 bool fLocked;
32 void* fPointer;
33 const size_t fBytes;
34 };
35
SkPoolDiscardableMemory(SkDiscardableMemoryPool * pool,void * pointer,size_t bytes)36 SkPoolDiscardableMemory::SkPoolDiscardableMemory(SkDiscardableMemoryPool* pool,
37 void* pointer,
38 size_t bytes)
39 : fPool(pool)
40 , fLocked(true)
41 , fPointer(pointer)
42 , fBytes(bytes) {
43 SkASSERT(fPool != NULL);
44 SkASSERT(fPointer != NULL);
45 SkASSERT(fBytes > 0);
46 fPool->ref();
47 }
48
~SkPoolDiscardableMemory()49 SkPoolDiscardableMemory::~SkPoolDiscardableMemory() {
50 SkASSERT(!fLocked); // contract for SkDiscardableMemory
51 fPool->free(this);
52 fPool->unref();
53 }
54
lock()55 bool SkPoolDiscardableMemory::lock() {
56 SkASSERT(!fLocked); // contract for SkDiscardableMemory
57 return fPool->lock(this);
58 }
59
data()60 void* SkPoolDiscardableMemory::data() {
61 SkASSERT(fLocked); // contract for SkDiscardableMemory
62 return fPointer;
63 }
64
unlock()65 void SkPoolDiscardableMemory::unlock() {
66 SkASSERT(fLocked); // contract for SkDiscardableMemory
67 fPool->unlock(this);
68 }
69
70 ////////////////////////////////////////////////////////////////////////////////
71
SkDiscardableMemoryPool(size_t budget,SkBaseMutex * mutex)72 SkDiscardableMemoryPool::SkDiscardableMemoryPool(size_t budget,
73 SkBaseMutex* mutex)
74 : fMutex(mutex)
75 , fBudget(budget)
76 , fUsed(0) {
77 #if LAZY_CACHE_STATS
78 fCacheHits = 0;
79 fCacheMisses = 0;
80 #endif // LAZY_CACHE_STATS
81 }
~SkDiscardableMemoryPool()82 SkDiscardableMemoryPool::~SkDiscardableMemoryPool() {
83 // SkPoolDiscardableMemory objects that belong to this pool are
84 // always deleted before deleting this pool since each one has a
85 // ref to the pool.
86 SkASSERT(fList.isEmpty());
87 }
88
dumpDownTo(size_t budget)89 void SkDiscardableMemoryPool::dumpDownTo(size_t budget) {
90 // assert((NULL = fMutex) || fMutex->isLocked());
91 // TODO(halcanary) implement bool fMutex::isLocked().
92 // WARNING: only call this function after aquiring lock.
93 if (fUsed <= budget) {
94 return;
95 }
96 typedef SkTInternalLList<SkPoolDiscardableMemory>::Iter Iter;
97 Iter iter;
98 SkPoolDiscardableMemory* cur = iter.init(fList, Iter::kTail_IterStart);
99 while ((fUsed > budget) && (NULL != cur)) {
100 if (!cur->fLocked) {
101 SkPoolDiscardableMemory* dm = cur;
102 SkASSERT(dm->fPointer != NULL);
103 sk_free(dm->fPointer);
104 dm->fPointer = NULL;
105 SkASSERT(fUsed >= dm->fBytes);
106 fUsed -= dm->fBytes;
107 cur = iter.prev();
108 // Purged DMs are taken out of the list. This saves times
109 // looking them up. Purged DMs are NOT deleted.
110 fList.remove(dm);
111 } else {
112 cur = iter.prev();
113 }
114 }
115 }
116
create(size_t bytes)117 SkDiscardableMemory* SkDiscardableMemoryPool::create(size_t bytes) {
118 void* addr = sk_malloc_flags(bytes, 0);
119 if (NULL == addr) {
120 return NULL;
121 }
122 SkPoolDiscardableMemory* dm = SkNEW_ARGS(SkPoolDiscardableMemory,
123 (this, addr, bytes));
124 SkAutoMutexAcquire autoMutexAcquire(fMutex);
125 fList.addToHead(dm);
126 fUsed += bytes;
127 this->dumpDownTo(fBudget);
128 return dm;
129 }
130
free(SkPoolDiscardableMemory * dm)131 void SkDiscardableMemoryPool::free(SkPoolDiscardableMemory* dm) {
132 // This is called by dm's destructor.
133 if (dm->fPointer != NULL) {
134 SkAutoMutexAcquire autoMutexAcquire(fMutex);
135 sk_free(dm->fPointer);
136 dm->fPointer = NULL;
137 SkASSERT(fUsed >= dm->fBytes);
138 fUsed -= dm->fBytes;
139 fList.remove(dm);
140 } else {
141 SkASSERT(!fList.isInList(dm));
142 }
143 }
144
lock(SkPoolDiscardableMemory * dm)145 bool SkDiscardableMemoryPool::lock(SkPoolDiscardableMemory* dm) {
146 SkASSERT(dm != NULL);
147 if (NULL == dm->fPointer) {
148 #if LAZY_CACHE_STATS
149 SkAutoMutexAcquire autoMutexAcquire(fMutex);
150 ++fCacheMisses;
151 #endif // LAZY_CACHE_STATS
152 return false;
153 }
154 SkAutoMutexAcquire autoMutexAcquire(fMutex);
155 if (NULL == dm->fPointer) {
156 // May have been purged while waiting for lock.
157 #if LAZY_CACHE_STATS
158 ++fCacheMisses;
159 #endif // LAZY_CACHE_STATS
160 return false;
161 }
162 dm->fLocked = true;
163 fList.remove(dm);
164 fList.addToHead(dm);
165 #if LAZY_CACHE_STATS
166 ++fCacheHits;
167 #endif // LAZY_CACHE_STATS
168 return true;
169 }
170
unlock(SkPoolDiscardableMemory * dm)171 void SkDiscardableMemoryPool::unlock(SkPoolDiscardableMemory* dm) {
172 SkASSERT(dm != NULL);
173 SkAutoMutexAcquire autoMutexAcquire(fMutex);
174 dm->fLocked = false;
175 this->dumpDownTo(fBudget);
176 }
177
getRAMUsed()178 size_t SkDiscardableMemoryPool::getRAMUsed() {
179 return fUsed;
180 }
setRAMBudget(size_t budget)181 void SkDiscardableMemoryPool::setRAMBudget(size_t budget) {
182 SkAutoMutexAcquire autoMutexAcquire(fMutex);
183 fBudget = budget;
184 this->dumpDownTo(fBudget);
185 }
dumpPool()186 void SkDiscardableMemoryPool::dumpPool() {
187 SkAutoMutexAcquire autoMutexAcquire(fMutex);
188 this->dumpDownTo(0);
189 }
190
191 ////////////////////////////////////////////////////////////////////////////////
192 SK_DECLARE_STATIC_MUTEX(gMutex);
create_pool(SkDiscardableMemoryPool ** pool)193 static void create_pool(SkDiscardableMemoryPool** pool) {
194 SkASSERT(NULL == *pool);
195 *pool = SkNEW_ARGS(SkDiscardableMemoryPool,
196 (SK_DEFAULT_GLOBAL_DISCARDABLE_MEMORY_POOL_SIZE,
197 &gMutex));
198 }
SkGetGlobalDiscardableMemoryPool()199 SkDiscardableMemoryPool* SkGetGlobalDiscardableMemoryPool() {
200 static SkDiscardableMemoryPool* gPool(NULL);
201 SK_DECLARE_STATIC_ONCE(create_pool_once);
202 SkOnce(&create_pool_once, create_pool, &gPool);
203 SkASSERT(NULL != gPool);
204 return gPool;
205 }
206
207 ////////////////////////////////////////////////////////////////////////////////
208