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// 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.
#include "base/callback.h"
#include "base/containers/hash_tables.h"
#include "base/containers/linked_list.h"
#include "base/memory/scoped_ptr.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 {
class CONTENT_EXPORT Span : public base::LinkNode<Span> {
base::DiscardableSharedMemory* shared_memory() { return shared_memory_; }
size_t start() const { return start_; }
size_t length() const { return length_; }
friend class DiscardableSharedMemoryHeap;
Span(base::DiscardableSharedMemory* shared_memory,
size_t start,
size_t length);
base::DiscardableSharedMemory* shared_memory_;
size_t start_;
size_t length_;
explicit DiscardableSharedMemoryHeap(size_t block_size);
// 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.
scoped_ptr<Span> Grow(scoped_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(scoped_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.
scoped_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.
scoped_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 tracing_process_id,
int32 segment_id);
class ScopedMemorySegment {
ScopedMemorySegment(DiscardableSharedMemoryHeap* heap,
scoped_ptr<base::DiscardableSharedMemory> shared_memory,
size_t size,
int32_t id,
const base::Closure& deleted_callback);
bool IsUsed() const;
bool IsResident() const;
// Used for dumping memory statistics from the segment to chrome://tracing.
void OnMemoryDump(base::trace_event::ProcessMemoryDump* pmd) const;
DiscardableSharedMemoryHeap* const heap_;
scoped_ptr<base::DiscardableSharedMemory> shared_memory_;
const size_t size_;
const int32_t id_;
const base::Closure deleted_callback_;
void InsertIntoFreeList(scoped_ptr<Span> span);
scoped_ptr<Span> RemoveFromFreeList(Span* span);
scoped_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];
} // namespace content