athena/resource_manager/memory_pressure_notifier.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 ATHENA_RESOURCE_MANAGER_MEMORY_PRESSURE_NOTIFIER_H_
   6 #define ATHENA_RESOURCE_MANAGER_MEMORY_PRESSURE_NOTIFIER_H_
   7
   8 #include "athena/athena_export.h"
   9 #include "athena/resource_manager/public/resource_manager.h"
  10 #include "base/memory/ref_counted.h"
  11 #include "base/memory/scoped_ptr.h"
  12 #include "base/timer/timer.h"
  13
  14 namespace athena {
  15
  16 class MemoryPressureNotifierImpl;
  17 class ResourceManagerDelegate;
  18
  19 ////////////////////////////////////////////////////////////////////////////////
  20 // MemoryPressureObserver
  21 //
  22 // This observer gets informed once about a |MEMORY_PRESSURE_LOW|. When the
  23 // pressure exceeds, the observer will get polled until |MEMORY_PRESSURE_LOW| is
  24 // reached again to counter memory consumption.
  25 class MemoryPressureObserver {
  26  public:
  27   MemoryPressureObserver() {}
  28   virtual ~MemoryPressureObserver() {}
  29
  30   // The observer.
  31   virtual void OnMemoryPressure(ResourceManager::MemoryPressure pressure) = 0;
  32
  33   // OS system interface functions. The delegate remains owned by the Observer.
  34   virtual ResourceManagerDelegate* GetDelegate() = 0;
  35 };
  36
  37
  38 ////////////////////////////////////////////////////////////////////////////////
  39 // MemoryPressureNotifier
  40 //
  41 // Class to handle the observation of our free memory. It notifies the owner of
  42 // memory fill level changes, so that it can take action to reduce memory by
  43 // reducing active activities.
  44 //
  45 // The observer will use 3 different fill levels: 50% full, 75% full and 90%
  46 // full.
  47 class ATHENA_EXPORT MemoryPressureNotifier {
  48  public:
  49   // The creator gets the |listener| object. Note that the ownership of the
  50   // listener object remains with the creator.
  51   explicit MemoryPressureNotifier(MemoryPressureObserver* listener);
  52   ~MemoryPressureNotifier();
  53
  54   // Stop observing the memory fill level.
  55   // May be safely called if StartObserving has not been called.
  56   void StopObserving();
  57
  58  private:
  59   // Starts observing the memory fill level.
  60   // Calls to StartObserving should always be matched with calls to
  61   // StopObserving.
  62   void StartObserving();
  63
  64   // The function which gets periodically be called to check any changes in the
  65   // memory pressure.
  66   void CheckMemoryPressure();
  67
  68   // Converts free percent of memory into a memory pressure value.
  69   ResourceManager::MemoryPressure GetMemoryPressureLevelFromFillLevel(
  70       int memory_fill_level);
  71
  72   base::RepeatingTimer<MemoryPressureNotifier> timer_;
  73
  74   // The listener which needs to be informed about memory pressure.
  75   MemoryPressureObserver* listener_;
  76
  77   // Our current memory pressure.
  78   ResourceManager::MemoryPressure current_pressure_;
  79
  80   DISALLOW_COPY_AND_ASSIGN(MemoryPressureNotifier);
  81 };
  82
  83 }  // namespace athena
  84
  85 #endif  // ATHENA_RESOURCE_MANAGER_MEMORY_PRESSURE_NOTIFIER_H_