content/common/discardable_shared_memory_heap.h

   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 CONTENT_COMMON_DISCARDABLE_SHARED_MEMORY_HEAP_H_
   6 #define CONTENT_COMMON_DISCARDABLE_SHARED_MEMORY_HEAP_H_
   7
   8 #include "base/callback.h"
   9 #include "base/containers/hash_tables.h"
  10 #include "base/containers/linked_list.h"
  11 #include "base/memory/scoped_ptr.h"
  12 #include "base/memory/scoped_vector.h"
  13 #include "base/trace_event/process_memory_dump.h"
  14 #include "content/common/content_export.h"
  15
  16 namespace base {
  17 class DiscardableSharedMemory;
  18 }
  19
  20 namespace content {
  21
  22 // Implements a heap of discardable shared memory. An array of free lists
  23 // is used to keep track of free blocks.
  24 class CONTENT_EXPORT DiscardableSharedMemoryHeap {
  25  public:
  26   class CONTENT_EXPORT Span : public base::LinkNode<Span> {
  27    public:
  28     ~Span();
  29
  30     base::DiscardableSharedMemory* shared_memory() { return shared_memory_; }
  31     size_t start() const { return start_; }
  32     size_t length() const { return length_; }
  33
  34    private:
  35     friend class DiscardableSharedMemoryHeap;
  36
  37     Span(base::DiscardableSharedMemory* shared_memory,
  38          size_t start,
  39          size_t length);
  40
  41     base::DiscardableSharedMemory* shared_memory_;
  42     size_t start_;
  43     size_t length_;
  44
  45     DISALLOW_COPY_AND_ASSIGN(Span);
  46   };
  47
  48   explicit DiscardableSharedMemoryHeap(size_t block_size);
  49   ~DiscardableSharedMemoryHeap();
  50
  51   // Grow heap using |shared_memory| and return a span for this new memory.
  52   // |shared_memory| must be aligned to the block size and |size| must be a
  53   // multiple of the block size. |deleted_callback| is called when
  54   // |shared_memory| has been deleted.
  55   scoped_ptr<Span> Grow(scoped_ptr<base::DiscardableSharedMemory> shared_memory,
  56                         size_t size,
  57                         int32_t id,
  58                         const base::Closure& deleted_callback);
  59
  60   // Merge |span| into the free lists. This will coalesce |span| with
  61   // neighboring free spans when possible.
  62   void MergeIntoFreeLists(scoped_ptr<Span> span);
  63
  64   // Split an allocated span into two spans, one of length |blocks| followed
  65   // by another span of length "span->length - blocks" blocks. Modifies |span|
  66   // to point to the first span of length |blocks|. Return second span.
  67   scoped_ptr<Span> Split(Span* span, size_t blocks);
  68
  69   // Search free lists for span that satisfies the request for |blocks| of
  70   // memory. If found, the span is removed from the free list and returned.
  71   // |slack| determines the fitness requirement. Only spans that are less
  72   // or equal to |blocks| + |slack| are considered, worse fitting spans are
  73   // ignored.
  74   scoped_ptr<Span> SearchFreeLists(size_t blocks, size_t slack);
  75
  76   // Release free shared memory segments.
  77   void ReleaseFreeMemory();
  78
  79   // Release shared memory segments that have been purged.
  80   void ReleasePurgedMemory();
  81
  82   // Returns total bytes of memory in heap.
  83   size_t GetSize() const;
  84
  85   // Returns bytes of memory currently in the free lists.
  86   size_t GetSizeOfFreeLists() const;
  87
  88   // Dumps memory statistics for chrome://tracing.
  89   bool OnMemoryDump(base::trace_event::ProcessMemoryDump* pmd);
  90
  91  private:
  92   class ScopedMemorySegment {
  93    public:
  94     ScopedMemorySegment(DiscardableSharedMemoryHeap* heap,
  95                         scoped_ptr<base::DiscardableSharedMemory> shared_memory,
  96                         size_t size,
  97                         int32_t id,
  98                         const base::Closure& deleted_callback);
  99     ~ScopedMemorySegment();
 100
 101     bool IsUsed() const;
 102     bool IsResident() const;
 103
 104     // Used for dumping memory statistics from the segment to chrome://tracing.
 105     void OnMemoryDump(base::trace_event::ProcessMemoryDump* pmd) const;
 106
 107    private:
 108     DiscardableSharedMemoryHeap* const heap_;
 109     scoped_ptr<base::DiscardableSharedMemory> shared_memory_;
 110     const size_t size_;
 111     const int32_t id_;
 112     const base::Closure deleted_callback_;
 113
 114     DISALLOW_COPY_AND_ASSIGN(ScopedMemorySegment);
 115   };
 116
 117   void InsertIntoFreeList(scoped_ptr<Span> span);
 118   scoped_ptr<Span> RemoveFromFreeList(Span* span);
 119   scoped_ptr<Span> Carve(Span* span, size_t blocks);
 120   void RegisterSpan(Span* span);
 121   void UnregisterSpan(Span* span);
 122   bool IsMemoryUsed(const base::DiscardableSharedMemory* shared_memory,
 123                     size_t size);
 124   bool IsMemoryResident(const base::DiscardableSharedMemory* shared_memory);
 125   void ReleaseMemory(const base::DiscardableSharedMemory* shared_memory,
 126                      size_t size);
 127
 128   // Dumps memory statistics about a memory segment for chrome://tracing.
 129   void OnMemoryDump(const base::DiscardableSharedMemory* shared_memory,
 130                     size_t size,
 131                     int32_t id,
 132                     base::trace_event::ProcessMemoryDump* pmd);
 133
 134   size_t block_size_;
 135   size_t num_blocks_;
 136   size_t num_free_blocks_;
 137
 138   // Vector of memory segments.
 139   ScopedVector<ScopedMemorySegment> memory_segments_;
 140
 141   // Mapping from first/last block of span to Span instance.
 142   typedef base::hash_map<size_t, Span*> SpanMap;
 143   SpanMap spans_;
 144
 145   // Array of linked-lists with free discardable memory regions. For i < 256,
 146   // where the 1st entry is located at index 0 of the array, the kth entry
 147   // is a free list of runs that consist of k blocks. The 256th entry is a
 148   // free list of runs that have length >= 256 blocks.
 149   base::LinkedList<Span> free_spans_[256];
 150
 151   DISALLOW_COPY_AND_ASSIGN(DiscardableSharedMemoryHeap);
 152 };
 153
 154 }  // namespace content
 155
 156 #endif  // CONTENT_COMMON_DISCARDABLE_SHARED_MEMORY_HEAP_H_