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       size_t size,
  45       DiscardableSharedMemoryId id,
  46       base::SharedMemoryHandle* shared_memory_handle);
  47
  48   // Call this to notify the manager that child process associated with
  49   // |process_handle| has deleted discardable memory segment with |id|.
  50   void ChildDeletedDiscardableSharedMemory(DiscardableSharedMemoryId id,
  51                                            base::ProcessHandle process_handle);
  52
  53   // Call this to notify the manager that child process associated with
  54   // |process_handle| has been removed. The manager will use this to release
  55   // memory segments allocated for child process to the OS.
  56   void ProcessRemoved(base::ProcessHandle process_handle);
  57
  58   // The maximum number of bytes of memory that may be allocated. This will
  59   // cause memory usage to be reduced if currently above |limit|.
  60   void SetMemoryLimit(size_t limit);
  61
  62   // Reduce memory usage if above current memory limit.
  63   void EnforceMemoryPolicy();
  64
  65   // Returns bytes of allocated discardable memory.
  66   size_t GetBytesAllocated();
  67
  68  private:
  69   class MemorySegment : public base::RefCountedThreadSafe<MemorySegment> {
  70    public:
  71     MemorySegment(scoped_ptr<base::DiscardableSharedMemory> memory);
  72
  73     base::DiscardableSharedMemory* memory() const { return memory_.get(); }
  74
  75    private:
  76     friend class base::RefCountedThreadSafe<MemorySegment>;
  77
  78     ~MemorySegment();
  79
  80     scoped_ptr<base::DiscardableSharedMemory> memory_;
  81
  82     DISALLOW_COPY_AND_ASSIGN(MemorySegment);
  83   };
  84
  85   static bool CompareMemoryUsageTime(const scoped_refptr<MemorySegment>& a,
  86                                      const scoped_refptr<MemorySegment>& b) {
  87     // In this system, LRU memory segment is evicted first.
  88     return a->memory()->last_known_usage() > b->memory()->last_known_usage();
  89   }
  90
  91   void AllocateLockedDiscardableSharedMemory(
  92       base::ProcessHandle process_handle,
  93       size_t size,
  94       DiscardableSharedMemoryId id,
  95       base::SharedMemoryHandle* shared_memory_handle);
  96   void DeletedDiscardableSharedMemory(DiscardableSharedMemoryId id,
  97                                       base::ProcessHandle process_handle);
  98   void OnMemoryPressure(
  99       base::MemoryPressureListener::MemoryPressureLevel memory_pressure_level);
 100   void ReduceMemoryUsageUntilWithinMemoryLimit();
 101   void ReduceMemoryUsageUntilWithinLimit(size_t limit);
 102   void ReleaseMemory(base::DiscardableSharedMemory* memory);
 103   void BytesAllocatedChanged(size_t new_bytes_allocated) const;
 104
 105   // Virtual for tests.
 106   virtual base::Time Now() const;
 107   virtual void ScheduleEnforceMemoryPolicy();
 108
 109   base::Lock lock_;
 110   typedef base::hash_map<DiscardableSharedMemoryId,
 111                          scoped_refptr<MemorySegment>> MemorySegmentMap;
 112   typedef base::hash_map<base::ProcessHandle, MemorySegmentMap> ProcessMap;
 113   ProcessMap processes_;
 114   // Note: The elements in |segments_| are arranged in such a way that they form
 115   // a heap. The LRU memory segment always first.
 116   typedef std::vector<scoped_refptr<MemorySegment>> MemorySegmentVector;
 117   MemorySegmentVector segments_;
 118   size_t memory_limit_;
 119   size_t bytes_allocated_;
 120   scoped_ptr<base::MemoryPressureListener> memory_pressure_listener_;
 121   bool enforce_memory_policy_pending_;
 122   base::WeakPtrFactory<HostDiscardableSharedMemoryManager> weak_ptr_factory_;
 123
 124   DISALLOW_COPY_AND_ASSIGN(HostDiscardableSharedMemoryManager);
 125 };
 126
 127 }  // namespace content
 128
 129 #endif  // CONTENT_COMMON_HOST_DISCARDABLE_SHARED_MEMORY_MANAGER_H_