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