athena/resource_manager/memory_pressure_notifier.h

   1 // Copyright (c) 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 "base/memory/ref_counted.h"
   9 #include "base/memory/scoped_ptr.h"
  10 #include "base/timer/timer.h"
  11
  12 namespace athena {
  13
  14 class MemoryPressureNotifierImpl;
  15 class ResourceManagerDelegate;
  16
  17 ////////////////////////////////////////////////////////////////////////////////
  18 // MemoryPressureObserver
  19 //
  20 // This observer gets informed once about a |MEMORY_PRESSURE_LOW|. When the
  21 // pressure exceeds, the observer will get polled until |MEMORY_PRESSURE_LOW| is
  22 // reached again to counter memory consumption.
  23 class MemoryPressureObserver {
  24  public:
  25   MemoryPressureObserver() {}
  26   virtual ~MemoryPressureObserver() {}
  27
  28   // The reported memory pressure. Note: The value is intentionally abstracted
  29   // since the real amount of free memory is only estimated (due to e.g. zram).
  30   enum MemoryPressure {
  31     MEMORY_PRESSURE_UNKNOWN,   // The memory pressure cannot be determined.
  32     MEMORY_PRESSURE_LOW,       // Single call if memory fill level is below 50%.
  33     MEMORY_PRESSURE_MODERATE,  // Polled for memory fill level of ~50 .. 75%.
  34     MEMORY_PRESSURE_HIGH,      // Polled for memory fill level of ~75% .. 90%.
  35     MEMORY_PRESSURE_CRITICAL,  // Polled for memory fill level of above ~90%.
  36   };
  37   // The observer.
  38   virtual void OnMemoryPressure(MemoryPressure pressure) = 0;
  39
  40   // OS system interface functions. The delegate remains owned by the Observer.
  41   virtual ResourceManagerDelegate* GetDelegate() = 0;
  42 };
  43
  44
  45 ////////////////////////////////////////////////////////////////////////////////
  46 // MemoryPressureNotifier
  47 //
  48 // Class to handle the observation of our free memory. It notifies the owner of
  49 // memory fill level changes, so that it can take action to reduce memory by
  50 // reducing active activities.
  51 //
  52 // The observer will use 3 different fill levels: 50% full, 75% full and 90%
  53 // full.
  54 class MemoryPressureNotifier {
  55  public:
  56   // The creator gets the |listener| object. Note that the ownership of the
  57   // listener object remains with the creator.
  58   explicit MemoryPressureNotifier(MemoryPressureObserver* listener);
  59   ~MemoryPressureNotifier();
  60
  61   // Stop observing the memory fill level.
  62   // May be safely called if StartObserving has not been called.
  63   void StopObserving();
  64
  65  private:
  66   // Starts observing the memory fill level.
  67   // Calls to StartObserving should always be matched with calls to
  68   // StopObserving.
  69   void StartObserving();
  70
  71   // The function which gets periodically be called to check any changes in the
  72   // memory pressure.
  73   void CheckMemoryPressure();
  74
  75   // Converts free percent of memory into a memory pressure value.
  76   MemoryPressureObserver::MemoryPressure GetMemoryPressureLevelFromFillLevel(
  77       int memory_fill_level);
  78
  79   base::RepeatingTimer<MemoryPressureNotifier> timer_;
  80
  81   // The listener which needs to be informed about memory pressure.
  82   MemoryPressureObserver* listener_;
  83
  84   // Our current memory pressure.
  85   MemoryPressureObserver::MemoryPressure current_pressure_;
  86
  87   DISALLOW_COPY_AND_ASSIGN(MemoryPressureNotifier);
  88 };
  89
  90 }  // namespace athena
  91
  92 #endif  // ATHENA_RESOURCE_MANAGER_MEMORY_PRESSURE_NOTIFIER_H_