1// Copyright 2014 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#ifndef BASE_MEMORY_DISCARDABLE_MEMORY_ASHMEM_ALLOCATOR_H_ 6#define BASE_MEMORY_DISCARDABLE_MEMORY_ASHMEM_ALLOCATOR_H_ 7 8#include <string> 9 10#include "base/base_export.h" 11#include "base/basictypes.h" 12#include "base/memory/scoped_ptr.h" 13#include "base/memory/scoped_vector.h" 14#include "base/synchronization/lock.h" 15 16namespace base { 17namespace internal { 18 19class AshmemRegion; 20 21// Internal class, whose instances are returned to the client of the allocator 22// (e.g. DiscardableMemoryAshmem), that mimicks the DiscardableMemory interface. 23class BASE_EXPORT_PRIVATE DiscardableAshmemChunk { 24 public: 25 ~DiscardableAshmemChunk(); 26 27 // Returns whether the memory is still resident. 28 bool Lock(); 29 30 void Unlock(); 31 32 void* Memory() const; 33 34 private: 35 friend class AshmemRegion; 36 37 DiscardableAshmemChunk(AshmemRegion* ashmem_region, 38 int fd, 39 void* address, 40 size_t offset, 41 size_t size); 42 43 AshmemRegion* const ashmem_region_; 44 const int fd_; 45 void* const address_; 46 const size_t offset_; 47 const size_t size_; 48 bool locked_; 49 50 DISALLOW_COPY_AND_ASSIGN(DiscardableAshmemChunk); 51}; 52 53// Ashmem regions are backed by a file (descriptor) therefore they are a limited 54// resource. This allocator minimizes the problem by allocating large ashmem 55// regions internally and returning smaller chunks to the client. 56// Allocated chunks are systematically aligned on a page boundary therefore this 57// allocator should not be used for small allocations. 58class BASE_EXPORT_PRIVATE DiscardableMemoryAshmemAllocator { 59 public: 60 // Note that |name| is only used for debugging/measurement purposes. 61 // |ashmem_region_size| is the size that will be used to create the underlying 62 // ashmem regions and is expected to be greater or equal than 32 MBytes. 63 DiscardableMemoryAshmemAllocator(const std::string& name, 64 size_t ashmem_region_size); 65 66 ~DiscardableMemoryAshmemAllocator(); 67 68 // Note that the allocator must outlive the returned DiscardableAshmemChunk 69 // instance. 70 scoped_ptr<DiscardableAshmemChunk> Allocate(size_t size); 71 72 // Returns the size of the last ashmem region which was created. This is used 73 // for testing only. 74 size_t last_ashmem_region_size() const; 75 76 private: 77 friend class AshmemRegion; 78 79 void DeleteAshmemRegion_Locked(AshmemRegion* region); 80 81 const std::string name_; 82 const size_t ashmem_region_size_; 83 mutable Lock lock_; 84 size_t last_ashmem_region_size_; 85 ScopedVector<AshmemRegion> ashmem_regions_; 86 87 DISALLOW_COPY_AND_ASSIGN(DiscardableMemoryAshmemAllocator); 88}; 89 90} // namespace internal 91} // namespace base 92 93#endif // BASE_MEMORY_DISCARDABLE_MEMORY_ASHMEM_ALLOCATOR_H_ 94