content/common/host_discardable_shared_memory_manager.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_HOST_DISCARDABLE_SHARED_MEMORY_MANAGER_H_
   6 #define CONTENT_COMMON_HOST_DISCARDABLE_SHARED_MEMORY_MANAGER_H_
   7
   8 #include <vector>
   9
  10 #include "base/containers/hash_tables.h"
  11 #include "base/memory/discardable_memory_allocator.h"
  12 #include "base/memory/discardable_shared_memory.h"
  13 #include "base/memory/memory_pressure_listener.h"
  14 #include "base/memory/ref_counted.h"
  15 #include "base/memory/shared_memory.h"
  16 #include "base/memory/weak_ptr.h"
  17 #include "base/process/process_handle.h"
  18 #include "base/synchronization/lock.h"
  19 #include "content/common/content_export.h"
  20
  21 namespace content {
  22 typedef int32_t DiscardableSharedMemoryId;
  23
  24 // Implementation of DiscardableMemoryAllocator that allocates and manages
  25 // discardable memory segments for the browser process and child processes.
  26 // This class is thread-safe and instances can safely be used on any thread.
  27 class CONTENT_EXPORT HostDiscardableSharedMemoryManager
  28     : public base::DiscardableMemoryAllocator {
  29  public:
  30   HostDiscardableSharedMemoryManager();
  31   ~HostDiscardableSharedMemoryManager() override;
  32
  33   // Returns a singleton instance.
  34   static HostDiscardableSharedMemoryManager* current();
  35
  36   // Overridden from base::DiscardableMemoryAllocator:
  37   scoped_ptr<base::DiscardableMemory> AllocateLockedDiscardableMemory(
  38       size_t size) override;
  39
  40   // This allocates a discardable memory segment for |process_handle|.
  41   // A valid shared memory handle is returned on success.
  42   void AllocateLockedDiscardableSharedMemoryForChild(
  43       base::ProcessHandle process_handle,
  44       int child_process_id,
  45       size_t size,
  46       DiscardableSharedMemoryId id,
  47       base::SharedMemoryHandle* shared_memory_handle);
  48
  49   // Call this to notify the manager that child process associated with
  50   // |child_process_id| has deleted discardable memory segment with |id|.
  51   void ChildDeletedDiscardableSharedMemory(DiscardableSharedMemoryId id,
  52                                            int child_process_id);
  53
  54   // Call this to notify the manager that child process associated with
  55   // |child_process_id| has been removed. The manager will use this to release
  56   // memory segments allocated for child process to the OS.
  57   void ProcessRemoved(int child_process_id);
  58
  59   // The maximum number of bytes of memory that may be allocated. This will
  60   // cause memory usage to be reduced if currently above |limit|.
  61   void SetMemoryLimit(size_t limit);
  62
  63   // Reduce memory usage if above current memory limit.
  64   void EnforceMemoryPolicy();
  65
  66   // Returns bytes of allocated discardable memory.
  67   size_t GetBytesAllocated();
  68
  69  private:
  70   class MemorySegment : public base::RefCountedThreadSafe<MemorySegment> {
  71    public:
  72     MemorySegment(scoped_ptr<base::DiscardableSharedMemory> memory);
  73
  74     base::DiscardableSharedMemory* memory() const { return memory_.get(); }
  75
  76    private:
  77     friend class base::RefCountedThreadSafe<MemorySegment>;
  78
  79     ~MemorySegment();
  80
  81     scoped_ptr<base::DiscardableSharedMemory> memory_;
  82
  83     DISALLOW_COPY_AND_ASSIGN(MemorySegment);
  84   };
  85
  86   static bool CompareMemoryUsageTime(const scoped_refptr<MemorySegment>& a,
  87                                      const scoped_refptr<MemorySegment>& b) {
  88     // In this system, LRU memory segment is evicted first.
  89     return a->memory()->last_known_usage() > b->memory()->last_known_usage();
  90   }
  91
  92   void AllocateLockedDiscardableSharedMemory(
  93       base::ProcessHandle process_handle,
  94       int client_process_id,
  95       size_t size,
  96       DiscardableSharedMemoryId id,
  97       base::SharedMemoryHandle* shared_memory_handle);
  98   void DeletedDiscardableSharedMemory(DiscardableSharedMemoryId id,
  99                                       int client_process_id);
 100   void OnMemoryPressure(
 101       base::MemoryPressureListener::MemoryPressureLevel memory_pressure_level);
 102   void ReduceMemoryUsageUntilWithinMemoryLimit();
 103   void ReduceMemoryUsageUntilWithinLimit(size_t limit);
 104   void ReleaseMemory(base::DiscardableSharedMemory* memory);
 105   void BytesAllocatedChanged(size_t new_bytes_allocated) const;
 106
 107   // Virtual for tests.
 108   virtual base::Time Now() const;
 109   virtual void ScheduleEnforceMemoryPolicy();
 110
 111   base::Lock lock_;
 112   typedef base::hash_map<DiscardableSharedMemoryId,
 113                          scoped_refptr<MemorySegment>> MemorySegmentMap;
 114   typedef base::hash_map<int, MemorySegmentMap> ProcessMap;
 115   ProcessMap processes_;
 116   // Note: The elements in |segments_| are arranged in such a way that they form
 117   // a heap. The LRU memory segment always first.
 118   typedef std::vector<scoped_refptr<MemorySegment>> MemorySegmentVector;
 119   MemorySegmentVector segments_;
 120   size_t memory_limit_;
 121   size_t bytes_allocated_;
 122   scoped_ptr<base::MemoryPressureListener> memory_pressure_listener_;
 123   bool enforce_memory_policy_pending_;
 124   base::WeakPtrFactory<HostDiscardableSharedMemoryManager> weak_ptr_factory_;
 125
 126   DISALLOW_COPY_AND_ASSIGN(HostDiscardableSharedMemoryManager);
 127 };
 128
 129 }  // namespace content
 130
 131 #endif  // CONTENT_COMMON_HOST_DISCARDABLE_SHARED_MEMORY_MANAGER_H_