Move discardable memory to //components from //content

content/common/discardable_shared_memory_heap.h

-// Copyright 2014 The Chromium Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style license that can be
-// found in the LICENSE file.
-
-#ifndef CONTENT_COMMON_DISCARDABLE_SHARED_MEMORY_HEAP_H_
-#define CONTENT_COMMON_DISCARDABLE_SHARED_MEMORY_HEAP_H_
-
-#include <stddef.h>
-#include <stdint.h>
-
-#include <memory>
-
-#include "base/callback.h"
-#include "base/containers/hash_tables.h"
-#include "base/containers/linked_list.h"
-#include "base/macros.h"
-#include "base/memory/scoped_vector.h"
-#include "base/trace_event/process_memory_dump.h"
-#include "content/common/content_export.h"
-
-namespace base {
-class DiscardableSharedMemory;
-}
-
-namespace content {
-
-// Implements a heap of discardable shared memory. An array of free lists
-// is used to keep track of free blocks.
-class CONTENT_EXPORT DiscardableSharedMemoryHeap {
- public:
-  class CONTENT_EXPORT Span : public base::LinkNode<Span> {
-   public:
-    ~Span();
-
-    base::DiscardableSharedMemory* shared_memory() { return shared_memory_; }
-    size_t start() const { return start_; }
-    size_t length() const { return length_; }
-    void set_is_locked(bool is_locked) { is_locked_ = is_locked; }
-
-   private:
-    friend class DiscardableSharedMemoryHeap;
-
-    Span(base::DiscardableSharedMemory* shared_memory,
-         size_t start,
-         size_t length);
-
-    base::DiscardableSharedMemory* shared_memory_;
-    size_t start_;
-    size_t length_;
-    bool is_locked_;
-
-    DISALLOW_COPY_AND_ASSIGN(Span);
-  };
-
-  explicit DiscardableSharedMemoryHeap(size_t block_size);
-  ~DiscardableSharedMemoryHeap();
-
-  // Grow heap using |shared_memory| and return a span for this new memory.
-  // |shared_memory| must be aligned to the block size and |size| must be a
-  // multiple of the block size. |deleted_callback| is called when
-  // |shared_memory| has been deleted.
-  std::unique_ptr<Span> Grow(
-      std::unique_ptr<base::DiscardableSharedMemory> shared_memory,
-      size_t size,
-      int32_t id,
-      const base::Closure& deleted_callback);
-
-  // Merge |span| into the free lists. This will coalesce |span| with
-  // neighboring free spans when possible.
-  void MergeIntoFreeLists(std::unique_ptr<Span> span);
-
-  // Split an allocated span into two spans, one of length |blocks| followed
-  // by another span of length "span->length - blocks" blocks. Modifies |span|
-  // to point to the first span of length |blocks|. Return second span.
-  std::unique_ptr<Span> Split(Span* span, size_t blocks);
-
-  // Search free lists for span that satisfies the request for |blocks| of
-  // memory. If found, the span is removed from the free list and returned.
-  // |slack| determines the fitness requirement. Only spans that are less
-  // or equal to |blocks| + |slack| are considered, worse fitting spans are
-  // ignored.
-  std::unique_ptr<Span> SearchFreeLists(size_t blocks, size_t slack);
-
-  // Release free shared memory segments.
-  void ReleaseFreeMemory();
-
-  // Release shared memory segments that have been purged.
-  void ReleasePurgedMemory();
-
-  // Returns total bytes of memory in heap.
-  size_t GetSize() const;
-
-  // Returns bytes of memory currently in the free lists.
-  size_t GetSizeOfFreeLists() const;
-
-  // Dumps memory statistics for chrome://tracing.
-  bool OnMemoryDump(base::trace_event::ProcessMemoryDump* pmd);
-
-  // Returns a unique identifier for a given tuple of (process id, segment id)
-  // that can be used to match memory dumps across different processes.
-  static base::trace_event::MemoryAllocatorDumpGuid GetSegmentGUIDForTracing(
-      uint64_t tracing_process_id,
-      int32_t segment_id);
-
-  // Returns a MemoryAllocatorDump for a given span on |pmd| with the size of
-  // the span.
-  base::trace_event::MemoryAllocatorDump* CreateMemoryAllocatorDump(
-      Span* span,
-      const char* name,
-      base::trace_event::ProcessMemoryDump* pmd) const;
-
- private:
-  class ScopedMemorySegment {
-   public:
-    ScopedMemorySegment(
-        DiscardableSharedMemoryHeap* heap,
-        std::unique_ptr<base::DiscardableSharedMemory> shared_memory,
-        size_t size,
-        int32_t id,
-        const base::Closure& deleted_callback);
-    ~ScopedMemorySegment();
-
-    bool IsUsed() const;
-    bool IsResident() const;
-
-    bool ContainsSpan(Span* span) const;
-
-    base::trace_event::MemoryAllocatorDump* CreateMemoryAllocatorDump(
-        Span* span,
-        size_t block_size,
-        const char* name,
-        base::trace_event::ProcessMemoryDump* pmd) const;
-
-    // Used for dumping memory statistics from the segment to chrome://tracing.
-    void OnMemoryDump(base::trace_event::ProcessMemoryDump* pmd) const;
-
-   private:
-    DiscardableSharedMemoryHeap* const heap_;
-    std::unique_ptr<base::DiscardableSharedMemory> shared_memory_;
-    const size_t size_;
-    const int32_t id_;
-    const base::Closure deleted_callback_;
-
-    DISALLOW_COPY_AND_ASSIGN(ScopedMemorySegment);
-  };
-
-  void InsertIntoFreeList(std::unique_ptr<Span> span);
-  std::unique_ptr<Span> RemoveFromFreeList(Span* span);
-  std::unique_ptr<Span> Carve(Span* span, size_t blocks);
-  void RegisterSpan(Span* span);
-  void UnregisterSpan(Span* span);
-  bool IsMemoryUsed(const base::DiscardableSharedMemory* shared_memory,
-                    size_t size);
-  bool IsMemoryResident(const base::DiscardableSharedMemory* shared_memory);
-  void ReleaseMemory(const base::DiscardableSharedMemory* shared_memory,
-                     size_t size);
-
-  // Dumps memory statistics about a memory segment for chrome://tracing.
-  void OnMemoryDump(const base::DiscardableSharedMemory* shared_memory,
-                    size_t size,
-                    int32_t segment_id,
-                    base::trace_event::ProcessMemoryDump* pmd);
-
-  size_t block_size_;
-  size_t num_blocks_;
-  size_t num_free_blocks_;
-
-  // Vector of memory segments.
-  ScopedVector<ScopedMemorySegment> memory_segments_;
-
-  // Mapping from first/last block of span to Span instance.
-  typedef base::hash_map<size_t, Span*> SpanMap;
-  SpanMap spans_;
-
-  // Array of linked-lists with free discardable memory regions. For i < 256,
-  // where the 1st entry is located at index 0 of the array, the kth entry
-  // is a free list of runs that consist of k blocks. The 256th entry is a
-  // free list of runs that have length >= 256 blocks.
-  base::LinkedList<Span> free_spans_[256];
-
-  DISALLOW_COPY_AND_ASSIGN(DiscardableSharedMemoryHeap);
-};
-
-}  // namespace content
-
-#endif  // CONTENT_COMMON_DISCARDABLE_SHARED_MEMORY_HEAP_H_