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| 1 // Copyright 2013 The Chromium Authors. All rights reserved. | |
| 2 // Use of this source code is governed by a BSD-style license that can be | |
| 3 // found in the LICENSE file. | |
| 4 | |
| 5 #include "base/memory/discardable_memory_ashmem_allocator.h" | |
| 6 | |
| 7 #include <sys/mman.h> | |
| 8 #include <unistd.h> | |
| 9 | |
| 10 #include <algorithm> | |
| 11 #include <cmath> | |
| 12 #include <limits> | |
| 13 #include <set> | |
| 14 #include <utility> | |
| 15 | |
| 16 #include "base/basictypes.h" | |
| 17 #include "base/containers/hash_tables.h" | |
| 18 #include "base/file_util.h" | |
| 19 #include "base/files/scoped_file.h" | |
| 20 #include "base/logging.h" | |
| 21 #include "base/memory/scoped_vector.h" | |
| 22 #include "third_party/ashmem/ashmem.h" | |
| 23 | |
| 24 // The allocator consists of three parts (classes): | |
| 25 // - DiscardableMemoryAshmemAllocator: entry point of all allocations (through | |
| 26 // its Allocate() method) that are dispatched to the AshmemRegion instances | |
| 27 // (which it owns). | |
| 28 // - AshmemRegion: manages allocations and destructions inside a single large | |
| 29 // (e.g. 32 MBytes) ashmem region. | |
| 30 // - DiscardableAshmemChunk: class mimicking the DiscardableMemory interface | |
| 31 // whose instances are returned to the client. | |
| 32 | |
| 33 namespace base { | |
| 34 namespace { | |
| 35 | |
| 36 // Only tolerate fragmentation in used chunks *caused by the client* (as opposed | |
| 37 // to the allocator when a free chunk is reused). The client can cause such | |
| 38 // fragmentation by e.g. requesting 4097 bytes. This size would be rounded up to | |
| 39 // 8192 by the allocator which would cause 4095 bytes of fragmentation (which is | |
| 40 // currently the maximum allowed). If the client requests 4096 bytes and a free | |
| 41 // chunk of 8192 bytes is available then the free chunk gets splitted into two | |
| 42 // pieces to minimize fragmentation (since 8192 - 4096 = 4096 which is greater | |
| 43 // than 4095). | |
| 44 // TODO(pliard): tune this if splitting chunks too often leads to performance | |
| 45 // issues. | |
| 46 const size_t kMaxChunkFragmentationBytes = 4096 - 1; | |
| 47 | |
| 48 const size_t kMinAshmemRegionSize = 32 * 1024 * 1024; | |
| 49 | |
| 50 // Returns 0 if the provided size is too high to be aligned. | |
| 51 size_t AlignToNextPage(size_t size) { | |
| 52 const size_t kPageSize = 4096; | |
| 53 DCHECK_EQ(static_cast<int>(kPageSize), getpagesize()); | |
| 54 if (size > std::numeric_limits<size_t>::max() - kPageSize + 1) | |
| 55 return 0; | |
| 56 const size_t mask = ~(kPageSize - 1); | |
| 57 return (size + kPageSize - 1) & mask; | |
| 58 } | |
| 59 | |
| 60 bool CreateAshmemRegion(const char* name, | |
| 61 size_t size, | |
| 62 int* out_fd, | |
| 63 void** out_address) { | |
| 64 base::ScopedFD fd(ashmem_create_region(name, size)); | |
| 65 if (!fd.is_valid()) { | |
| 66 DLOG(ERROR) << "ashmem_create_region() failed"; | |
| 67 return false; | |
| 68 } | |
| 69 | |
| 70 const int err = ashmem_set_prot_region(fd.get(), PROT_READ | PROT_WRITE); | |
| 71 if (err < 0) { | |
| 72 DLOG(ERROR) << "Error " << err << " when setting protection of ashmem"; | |
| 73 return false; | |
| 74 } | |
| 75 | |
| 76 // There is a problem using MAP_PRIVATE here. As we are constantly calling | |
| 77 // Lock() and Unlock(), data could get lost if they are not written to the | |
| 78 // underlying file when Unlock() gets called. | |
| 79 void* const address = mmap( | |
| 80 NULL, size, PROT_READ | PROT_WRITE, MAP_SHARED, fd.get(), 0); | |
| 81 if (address == MAP_FAILED) { | |
| 82 DPLOG(ERROR) << "Failed to map memory."; | |
| 83 return false; | |
| 84 } | |
| 85 | |
| 86 *out_fd = fd.release(); | |
| 87 *out_address = address; | |
| 88 return true; | |
| 89 } | |
| 90 | |
| 91 bool CloseAshmemRegion(int fd, size_t size, void* address) { | |
| 92 if (munmap(address, size) == -1) { | |
| 93 DPLOG(ERROR) << "Failed to unmap memory."; | |
| 94 close(fd); | |
| 95 return false; | |
| 96 } | |
| 97 return close(fd) == 0; | |
| 98 } | |
| 99 | |
| 100 bool LockAshmemRegion(int fd, size_t off, size_t size) { | |
| 101 return ashmem_pin_region(fd, off, size) != ASHMEM_WAS_PURGED; | |
| 102 } | |
| 103 | |
| 104 bool UnlockAshmemRegion(int fd, size_t off, size_t size) { | |
| 105 const int failed = ashmem_unpin_region(fd, off, size); | |
| 106 if (failed) | |
| 107 DLOG(ERROR) << "Failed to unpin memory."; | |
| 108 return !failed; | |
| 109 } | |
| 110 | |
| 111 } // namespace | |
| 112 | |
| 113 namespace internal { | |
| 114 | |
| 115 class AshmemRegion { | |
| 116 public: | |
| 117 // Note that |allocator| must outlive |this|. | |
| 118 static scoped_ptr<AshmemRegion> Create( | |
| 119 size_t size, | |
| 120 const std::string& name, | |
| 121 DiscardableMemoryAshmemAllocator* allocator) { | |
| 122 DCHECK_EQ(size, AlignToNextPage(size)); | |
| 123 int fd; | |
| 124 void* base; | |
| 125 if (!CreateAshmemRegion(name.c_str(), size, &fd, &base)) | |
| 126 return scoped_ptr<AshmemRegion>(); | |
| 127 return make_scoped_ptr(new AshmemRegion(fd, size, base, allocator)); | |
| 128 } | |
| 129 | |
| 130 ~AshmemRegion() { | |
| 131 const bool result = CloseAshmemRegion(fd_, size_, base_); | |
| 132 DCHECK(result); | |
| 133 DCHECK(!highest_allocated_chunk_); | |
| 134 } | |
| 135 | |
| 136 // Returns a new instance of DiscardableAshmemChunk whose size is greater or | |
| 137 // equal than |actual_size| (which is expected to be greater or equal than | |
| 138 // |client_requested_size|). | |
| 139 // Allocation works as follows: | |
| 140 // 1) Reuse a previously freed chunk and return it if it succeeded. See | |
| 141 // ReuseFreeChunk_Locked() below for more information. | |
| 142 // 2) If no free chunk could be reused and the region is not big enough for | |
| 143 // the requested size then NULL is returned. | |
| 144 // 3) If there is enough room in the ashmem region then a new chunk is | |
| 145 // returned. This new chunk starts at |offset_| which is the end of the | |
| 146 // previously highest chunk in the region. | |
| 147 scoped_ptr<DiscardableAshmemChunk> Allocate_Locked( | |
| 148 size_t client_requested_size, | |
| 149 size_t actual_size) { | |
| 150 DCHECK_LE(client_requested_size, actual_size); | |
| 151 allocator_->lock_.AssertAcquired(); | |
| 152 | |
| 153 // Check that the |highest_allocated_chunk_| field doesn't contain a stale | |
| 154 // pointer. It should point to either a free chunk or a used chunk. | |
| 155 DCHECK(!highest_allocated_chunk_ || | |
| 156 address_to_free_chunk_map_.find(highest_allocated_chunk_) != | |
| 157 address_to_free_chunk_map_.end() || | |
| 158 used_to_previous_chunk_map_.find(highest_allocated_chunk_) != | |
| 159 used_to_previous_chunk_map_.end()); | |
| 160 | |
| 161 scoped_ptr<DiscardableAshmemChunk> memory = ReuseFreeChunk_Locked( | |
| 162 client_requested_size, actual_size); | |
| 163 if (memory) | |
| 164 return memory.Pass(); | |
| 165 | |
| 166 if (size_ - offset_ < actual_size) { | |
| 167 // This region does not have enough space left to hold the requested size. | |
| 168 return scoped_ptr<DiscardableAshmemChunk>(); | |
| 169 } | |
| 170 | |
| 171 void* const address = static_cast<char*>(base_) + offset_; | |
| 172 memory.reset( | |
| 173 new DiscardableAshmemChunk(this, fd_, address, offset_, actual_size)); | |
| 174 | |
| 175 used_to_previous_chunk_map_.insert( | |
| 176 std::make_pair(address, highest_allocated_chunk_)); | |
| 177 highest_allocated_chunk_ = address; | |
| 178 offset_ += actual_size; | |
| 179 DCHECK_LE(offset_, size_); | |
| 180 return memory.Pass(); | |
| 181 } | |
| 182 | |
| 183 void OnChunkDeletion(void* chunk, size_t size) { | |
| 184 AutoLock auto_lock(allocator_->lock_); | |
| 185 MergeAndAddFreeChunk_Locked(chunk, size); | |
| 186 // Note that |this| might be deleted beyond this point. | |
| 187 } | |
| 188 | |
| 189 private: | |
| 190 struct FreeChunk { | |
| 191 FreeChunk() : previous_chunk(NULL), start(NULL), size(0) {} | |
| 192 | |
| 193 explicit FreeChunk(size_t size) | |
| 194 : previous_chunk(NULL), | |
| 195 start(NULL), | |
| 196 size(size) { | |
| 197 } | |
| 198 | |
| 199 FreeChunk(void* previous_chunk, void* start, size_t size) | |
| 200 : previous_chunk(previous_chunk), | |
| 201 start(start), | |
| 202 size(size) { | |
| 203 DCHECK_LT(previous_chunk, start); | |
| 204 } | |
| 205 | |
| 206 void* const previous_chunk; | |
| 207 void* const start; | |
| 208 const size_t size; | |
| 209 | |
| 210 bool is_null() const { return !start; } | |
| 211 | |
| 212 bool operator<(const FreeChunk& other) const { | |
| 213 return size < other.size; | |
| 214 } | |
| 215 }; | |
| 216 | |
| 217 // Note that |allocator| must outlive |this|. | |
| 218 AshmemRegion(int fd, | |
| 219 size_t size, | |
| 220 void* base, | |
| 221 DiscardableMemoryAshmemAllocator* allocator) | |
| 222 : fd_(fd), | |
| 223 size_(size), | |
| 224 base_(base), | |
| 225 allocator_(allocator), | |
| 226 highest_allocated_chunk_(NULL), | |
| 227 offset_(0) { | |
| 228 DCHECK_GE(fd_, 0); | |
| 229 DCHECK_GE(size, kMinAshmemRegionSize); | |
| 230 DCHECK(base); | |
| 231 DCHECK(allocator); | |
| 232 } | |
| 233 | |
| 234 // Tries to reuse a previously freed chunk by doing a closest size match. | |
| 235 scoped_ptr<DiscardableAshmemChunk> ReuseFreeChunk_Locked( | |
| 236 size_t client_requested_size, | |
| 237 size_t actual_size) { | |
| 238 allocator_->lock_.AssertAcquired(); | |
| 239 const FreeChunk reused_chunk = RemoveFreeChunkFromIterator_Locked( | |
| 240 free_chunks_.lower_bound(FreeChunk(actual_size))); | |
| 241 if (reused_chunk.is_null()) | |
| 242 return scoped_ptr<DiscardableAshmemChunk>(); | |
| 243 | |
| 244 used_to_previous_chunk_map_.insert( | |
| 245 std::make_pair(reused_chunk.start, reused_chunk.previous_chunk)); | |
| 246 size_t reused_chunk_size = reused_chunk.size; | |
| 247 // |client_requested_size| is used below rather than |actual_size| to | |
| 248 // reflect the amount of bytes that would not be usable by the client (i.e. | |
| 249 // wasted). Using |actual_size| instead would not allow us to detect | |
| 250 // fragmentation caused by the client if he did misaligned allocations. | |
| 251 DCHECK_GE(reused_chunk.size, client_requested_size); | |
| 252 const size_t fragmentation_bytes = | |
| 253 reused_chunk.size - client_requested_size; | |
| 254 | |
| 255 if (fragmentation_bytes > kMaxChunkFragmentationBytes) { | |
| 256 // Split the free chunk being recycled so that its unused tail doesn't get | |
| 257 // reused (i.e. locked) which would prevent it from being evicted under | |
| 258 // memory pressure. | |
| 259 reused_chunk_size = actual_size; | |
| 260 void* const new_chunk_start = | |
| 261 static_cast<char*>(reused_chunk.start) + actual_size; | |
| 262 if (reused_chunk.start == highest_allocated_chunk_) { | |
| 263 // We also need to update the pointer to the highest allocated chunk in | |
| 264 // case we are splitting the highest chunk. | |
| 265 highest_allocated_chunk_ = new_chunk_start; | |
| 266 } | |
| 267 DCHECK_GT(reused_chunk.size, actual_size); | |
| 268 const size_t new_chunk_size = reused_chunk.size - actual_size; | |
| 269 // Note that merging is not needed here since there can't be contiguous | |
| 270 // free chunks at this point. | |
| 271 AddFreeChunk_Locked( | |
| 272 FreeChunk(reused_chunk.start, new_chunk_start, new_chunk_size)); | |
| 273 } | |
| 274 | |
| 275 const size_t offset = | |
| 276 static_cast<char*>(reused_chunk.start) - static_cast<char*>(base_); | |
| 277 LockAshmemRegion(fd_, offset, reused_chunk_size); | |
| 278 scoped_ptr<DiscardableAshmemChunk> memory( | |
| 279 new DiscardableAshmemChunk( | |
| 280 this, fd_, reused_chunk.start, offset, reused_chunk_size)); | |
| 281 return memory.Pass(); | |
| 282 } | |
| 283 | |
| 284 // Makes the chunk identified with the provided arguments free and possibly | |
| 285 // merges this chunk with the previous and next contiguous ones. | |
| 286 // If the provided chunk is the only one used (and going to be freed) in the | |
| 287 // region then the internal ashmem region is closed so that the underlying | |
| 288 // physical pages are immediately released. | |
| 289 // Note that free chunks are unlocked therefore they can be reclaimed by the | |
| 290 // kernel if needed (under memory pressure) but they are not immediately | |
| 291 // released unfortunately since madvise(MADV_REMOVE) and | |
| 292 // fallocate(FALLOC_FL_PUNCH_HOLE) don't seem to work on ashmem. This might | |
| 293 // change in versions of kernel >=3.5 though. The fact that free chunks are | |
| 294 // not immediately released is the reason why we are trying to minimize | |
| 295 // fragmentation in order not to cause "artificial" memory pressure. | |
| 296 void MergeAndAddFreeChunk_Locked(void* chunk, size_t size) { | |
| 297 allocator_->lock_.AssertAcquired(); | |
| 298 size_t new_free_chunk_size = size; | |
| 299 // Merge with the previous chunk. | |
| 300 void* first_free_chunk = chunk; | |
| 301 DCHECK(!used_to_previous_chunk_map_.empty()); | |
| 302 const hash_map<void*, void*>::iterator previous_chunk_it = | |
| 303 used_to_previous_chunk_map_.find(chunk); | |
| 304 DCHECK(previous_chunk_it != used_to_previous_chunk_map_.end()); | |
| 305 void* previous_chunk = previous_chunk_it->second; | |
| 306 used_to_previous_chunk_map_.erase(previous_chunk_it); | |
| 307 | |
| 308 if (previous_chunk) { | |
| 309 const FreeChunk free_chunk = RemoveFreeChunk_Locked(previous_chunk); | |
| 310 if (!free_chunk.is_null()) { | |
| 311 new_free_chunk_size += free_chunk.size; | |
| 312 first_free_chunk = previous_chunk; | |
| 313 if (chunk == highest_allocated_chunk_) | |
| 314 highest_allocated_chunk_ = previous_chunk; | |
| 315 | |
| 316 // There should not be more contiguous previous free chunks. | |
| 317 previous_chunk = free_chunk.previous_chunk; | |
| 318 DCHECK(!address_to_free_chunk_map_.count(previous_chunk)); | |
| 319 } | |
| 320 } | |
| 321 | |
| 322 // Merge with the next chunk if free and present. | |
| 323 void* next_chunk = static_cast<char*>(chunk) + size; | |
| 324 const FreeChunk next_free_chunk = RemoveFreeChunk_Locked(next_chunk); | |
| 325 if (!next_free_chunk.is_null()) { | |
| 326 new_free_chunk_size += next_free_chunk.size; | |
| 327 if (next_free_chunk.start == highest_allocated_chunk_) | |
| 328 highest_allocated_chunk_ = first_free_chunk; | |
| 329 | |
| 330 // Same as above. | |
| 331 DCHECK(!address_to_free_chunk_map_.count(static_cast<char*>(next_chunk) + | |
| 332 next_free_chunk.size)); | |
| 333 } | |
| 334 | |
| 335 const bool whole_ashmem_region_is_free = | |
| 336 used_to_previous_chunk_map_.empty(); | |
| 337 if (!whole_ashmem_region_is_free) { | |
| 338 AddFreeChunk_Locked( | |
| 339 FreeChunk(previous_chunk, first_free_chunk, new_free_chunk_size)); | |
| 340 return; | |
| 341 } | |
| 342 | |
| 343 // The whole ashmem region is free thus it can be deleted. | |
| 344 DCHECK_EQ(base_, first_free_chunk); | |
| 345 DCHECK_EQ(base_, highest_allocated_chunk_); | |
| 346 DCHECK(free_chunks_.empty()); | |
| 347 DCHECK(address_to_free_chunk_map_.empty()); | |
| 348 DCHECK(used_to_previous_chunk_map_.empty()); | |
| 349 highest_allocated_chunk_ = NULL; | |
| 350 allocator_->DeleteAshmemRegion_Locked(this); // Deletes |this|. | |
| 351 } | |
| 352 | |
| 353 void AddFreeChunk_Locked(const FreeChunk& free_chunk) { | |
| 354 allocator_->lock_.AssertAcquired(); | |
| 355 const std::multiset<FreeChunk>::iterator it = free_chunks_.insert( | |
| 356 free_chunk); | |
| 357 address_to_free_chunk_map_.insert(std::make_pair(free_chunk.start, it)); | |
| 358 // Update the next used contiguous chunk, if any, since its previous chunk | |
| 359 // may have changed due to free chunks merging/splitting. | |
| 360 void* const next_used_contiguous_chunk = | |
| 361 static_cast<char*>(free_chunk.start) + free_chunk.size; | |
| 362 hash_map<void*, void*>::iterator previous_it = | |
| 363 used_to_previous_chunk_map_.find(next_used_contiguous_chunk); | |
| 364 if (previous_it != used_to_previous_chunk_map_.end()) | |
| 365 previous_it->second = free_chunk.start; | |
| 366 } | |
| 367 | |
| 368 // Finds and removes the free chunk, if any, whose start address is | |
| 369 // |chunk_start|. Returns a copy of the unlinked free chunk or a free chunk | |
| 370 // whose content is null if it was not found. | |
| 371 FreeChunk RemoveFreeChunk_Locked(void* chunk_start) { | |
| 372 allocator_->lock_.AssertAcquired(); | |
| 373 const hash_map< | |
| 374 void*, std::multiset<FreeChunk>::iterator>::iterator it = | |
| 375 address_to_free_chunk_map_.find(chunk_start); | |
| 376 if (it == address_to_free_chunk_map_.end()) | |
| 377 return FreeChunk(); | |
| 378 return RemoveFreeChunkFromIterator_Locked(it->second); | |
| 379 } | |
| 380 | |
| 381 // Same as above but takes an iterator in. | |
| 382 FreeChunk RemoveFreeChunkFromIterator_Locked( | |
| 383 std::multiset<FreeChunk>::iterator free_chunk_it) { | |
| 384 allocator_->lock_.AssertAcquired(); | |
| 385 if (free_chunk_it == free_chunks_.end()) | |
| 386 return FreeChunk(); | |
| 387 DCHECK(free_chunk_it != free_chunks_.end()); | |
| 388 const FreeChunk free_chunk(*free_chunk_it); | |
| 389 address_to_free_chunk_map_.erase(free_chunk_it->start); | |
| 390 free_chunks_.erase(free_chunk_it); | |
| 391 return free_chunk; | |
| 392 } | |
| 393 | |
| 394 const int fd_; | |
| 395 const size_t size_; | |
| 396 void* const base_; | |
| 397 DiscardableMemoryAshmemAllocator* const allocator_; | |
| 398 // Points to the chunk with the highest address in the region. This pointer | |
| 399 // needs to be carefully updated when chunks are merged/split. | |
| 400 void* highest_allocated_chunk_; | |
| 401 // Points to the end of |highest_allocated_chunk_|. | |
| 402 size_t offset_; | |
| 403 // Allows free chunks recycling (lookup, insertion and removal) in O(log N). | |
| 404 // Note that FreeChunk values are indexed by their size and also note that | |
| 405 // multiple free chunks can have the same size (which is why multiset<> is | |
| 406 // used instead of e.g. set<>). | |
| 407 std::multiset<FreeChunk> free_chunks_; | |
| 408 // Used while merging free contiguous chunks to erase free chunks (from their | |
| 409 // start address) in constant time. Note that multiset<>::{insert,erase}() | |
| 410 // don't invalidate iterators (except the one for the element being removed | |
| 411 // obviously). | |
| 412 hash_map< | |
| 413 void*, std::multiset<FreeChunk>::iterator> address_to_free_chunk_map_; | |
| 414 // Maps the address of *used* chunks to the address of their previous | |
| 415 // contiguous chunk. | |
| 416 hash_map<void*, void*> used_to_previous_chunk_map_; | |
| 417 | |
| 418 DISALLOW_COPY_AND_ASSIGN(AshmemRegion); | |
| 419 }; | |
| 420 | |
| 421 DiscardableAshmemChunk::~DiscardableAshmemChunk() { | |
| 422 if (locked_) | |
| 423 UnlockAshmemRegion(fd_, offset_, size_); | |
| 424 ashmem_region_->OnChunkDeletion(address_, size_); | |
| 425 } | |
| 426 | |
| 427 bool DiscardableAshmemChunk::Lock() { | |
| 428 DCHECK(!locked_); | |
| 429 locked_ = true; | |
| 430 return LockAshmemRegion(fd_, offset_, size_); | |
| 431 } | |
| 432 | |
| 433 void DiscardableAshmemChunk::Unlock() { | |
| 434 DCHECK(locked_); | |
| 435 locked_ = false; | |
| 436 UnlockAshmemRegion(fd_, offset_, size_); | |
| 437 } | |
| 438 | |
| 439 void* DiscardableAshmemChunk::Memory() const { | |
| 440 return address_; | |
| 441 } | |
| 442 | |
| 443 // Note that |ashmem_region| must outlive |this|. | |
| 444 DiscardableAshmemChunk::DiscardableAshmemChunk(AshmemRegion* ashmem_region, | |
| 445 int fd, | |
| 446 void* address, | |
| 447 size_t offset, | |
| 448 size_t size) | |
| 449 : ashmem_region_(ashmem_region), | |
| 450 fd_(fd), | |
| 451 address_(address), | |
| 452 offset_(offset), | |
| 453 size_(size), | |
| 454 locked_(true) { | |
| 455 } | |
| 456 | |
| 457 DiscardableMemoryAshmemAllocator::DiscardableMemoryAshmemAllocator( | |
| 458 const std::string& name, | |
| 459 size_t ashmem_region_size) | |
| 460 : name_(name), | |
| 461 ashmem_region_size_( | |
| 462 std::max(kMinAshmemRegionSize, AlignToNextPage(ashmem_region_size))), | |
| 463 last_ashmem_region_size_(0) { | |
| 464 DCHECK_GE(ashmem_region_size_, kMinAshmemRegionSize); | |
| 465 } | |
| 466 | |
| 467 DiscardableMemoryAshmemAllocator::~DiscardableMemoryAshmemAllocator() { | |
| 468 DCHECK(ashmem_regions_.empty()); | |
| 469 } | |
| 470 | |
| 471 scoped_ptr<DiscardableAshmemChunk> DiscardableMemoryAshmemAllocator::Allocate( | |
| 472 size_t size) { | |
| 473 const size_t aligned_size = AlignToNextPage(size); | |
| 474 if (!aligned_size) | |
| 475 return scoped_ptr<DiscardableAshmemChunk>(); | |
| 476 // TODO(pliard): make this function less naive by e.g. moving the free chunks | |
| 477 // multiset to the allocator itself in order to decrease even more | |
| 478 // fragmentation/speedup allocation. Note that there should not be more than a | |
| 479 // couple (=5) of AshmemRegion instances in practice though. | |
| 480 AutoLock auto_lock(lock_); | |
| 481 DCHECK_LE(ashmem_regions_.size(), 5U); | |
| 482 for (ScopedVector<AshmemRegion>::iterator it = ashmem_regions_.begin(); | |
| 483 it != ashmem_regions_.end(); ++it) { | |
| 484 scoped_ptr<DiscardableAshmemChunk> memory( | |
| 485 (*it)->Allocate_Locked(size, aligned_size)); | |
| 486 if (memory) | |
| 487 return memory.Pass(); | |
| 488 } | |
| 489 // The creation of the (large) ashmem region might fail if the address space | |
| 490 // is too fragmented. In case creation fails the allocator retries by | |
| 491 // repetitively dividing the size by 2. | |
| 492 const size_t min_region_size = std::max(kMinAshmemRegionSize, aligned_size); | |
| 493 for (size_t region_size = std::max(ashmem_region_size_, aligned_size); | |
| 494 region_size >= min_region_size; | |
| 495 region_size = AlignToNextPage(region_size / 2)) { | |
| 496 scoped_ptr<AshmemRegion> new_region( | |
| 497 AshmemRegion::Create(region_size, name_.c_str(), this)); | |
| 498 if (!new_region) | |
| 499 continue; | |
| 500 last_ashmem_region_size_ = region_size; | |
| 501 ashmem_regions_.push_back(new_region.release()); | |
| 502 return ashmem_regions_.back()->Allocate_Locked(size, aligned_size); | |
| 503 } | |
| 504 // TODO(pliard): consider adding an histogram to see how often this happens. | |
| 505 return scoped_ptr<DiscardableAshmemChunk>(); | |
| 506 } | |
| 507 | |
| 508 size_t DiscardableMemoryAshmemAllocator::last_ashmem_region_size() const { | |
| 509 AutoLock auto_lock(lock_); | |
| 510 return last_ashmem_region_size_; | |
| 511 } | |
| 512 | |
| 513 void DiscardableMemoryAshmemAllocator::DeleteAshmemRegion_Locked( | |
| 514 AshmemRegion* region) { | |
| 515 lock_.AssertAcquired(); | |
| 516 // Note that there should not be more than a couple of ashmem region instances | |
| 517 // in |ashmem_regions_|. | |
| 518 DCHECK_LE(ashmem_regions_.size(), 5U); | |
| 519 const ScopedVector<AshmemRegion>::iterator it = std::find( | |
| 520 ashmem_regions_.begin(), ashmem_regions_.end(), region); | |
| 521 DCHECK_NE(ashmem_regions_.end(), it); | |
| 522 std::swap(*it, ashmem_regions_.back()); | |
| 523 ashmem_regions_.pop_back(); | |
| 524 } | |
| 525 | |
| 526 } // namespace internal | |
| 527 } // namespace base | |
| OLD | NEW |
|---|
Chromium Code Reviews
Issue 257383004:
Revert 267170 "Use DiscardableMemoryManager on Android." (Closed)
Base URL: svn://svn.chromium.org/chrome/