base/memory/memory_pressure_monitor_chromeos.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 BASE_MEMORY_MEMORY_PRESSURE_MONITOR_CHROMEOS_H_
   6 #define BASE_MEMORY_MEMORY_PRESSURE_MONITOR_CHROMEOS_H_
   7
   8 #include "base/base_export.h"
   9 #include "base/files/scoped_file.h"
  10 #include "base/gtest_prod_util.h"
  11 #include "base/macros.h"
  12 #include "base/memory/memory_pressure_listener.h"
  13 #include "base/memory/memory_pressure_monitor.h"
  14 #include "base/memory/weak_ptr.h"
  15 #include "base/timer/timer.h"
  16
  17 namespace base {
  18 namespace chromeos {
  19
  20 class TestMemoryPressureMonitor;
  21
  22 ////////////////////////////////////////////////////////////////////////////////
  23 // MemoryPressureMonitor
  24 //
  25 // A class to handle the observation of our free memory. It notifies the
  26 // MemoryPressureListener of memory fill level changes, so that it can take
  27 // action to reduce memory resources accordingly.
  28 //
  29 class BASE_EXPORT MemoryPressureMonitor : public base::MemoryPressureMonitor {
  30  public:
  31   using GetUsedMemoryInPercentCallback = int (*)();
  32
  33   // There are two memory pressure events:
  34   // MODERATE - which will mainly release caches.
  35   // CRITICAL - which will discard tabs.
  36   // The |MemoryPressureThresholds| enum selects the strategy of firing these
  37   // events: A conservative strategy will keep as much content in memory as
  38   // possible (causing the system to swap to zram) and an aggressive strategy
  39   // will release memory earlier to avoid swapping.
  40   enum MemoryPressureThresholds {
  41     // Use the system default.
  42     THRESHOLD_DEFAULT = 0,
  43     // Try to keep as much content in memory as possible.
  44     THRESHOLD_CONSERVATIVE = 1,
  45     // Discard caches earlier, allowing to keep more tabs in memory.
  46     THRESHOLD_AGGRESSIVE_CACHE_DISCARD = 2,
  47     // Discard tabs earlier, allowing the system to get faster.
  48     THRESHOLD_AGGRESSIVE_TAB_DISCARD = 3,
  49     // Discard caches and tabs earlier to allow the system to be faster.
  50     THRESHOLD_AGGRESSIVE = 4
  51   };
  52
  53   explicit MemoryPressureMonitor(MemoryPressureThresholds thresholds);
  54   ~MemoryPressureMonitor() override;
  55
  56   // Redo the memory pressure calculation soon and call again if a critical
  57   // memory pressure prevails. Note that this call will trigger an asynchronous
  58   // action which gives the system time to release memory back into the pool.
  59   void ScheduleEarlyCheck();
  60
  61   // Get the current memory pressure level.
  62   MemoryPressureListener::MemoryPressureLevel GetCurrentPressureLevel() const
  63       override;
  64
  65   // Returns a type-casted version of the current memory pressure monitor. A
  66   // simple wrapper to base::MemoryPressureMonitor::Get.
  67   static MemoryPressureMonitor* Get();
  68
  69  private:
  70   friend TestMemoryPressureMonitor;
  71   // Starts observing the memory fill level.
  72   // Calls to StartObserving should always be matched with calls to
  73   // StopObserving.
  74   void StartObserving();
  75
  76   // Stop observing the memory fill level.
  77   // May be safely called if StartObserving has not been called.
  78   void StopObserving();
  79
  80   // The function which gets periodically called to check any changes in the
  81   // memory pressure. It will report pressure changes as well as continuous
  82   // critical pressure levels.
  83   void CheckMemoryPressure();
  84
  85   // The function periodically checks the memory pressure changes and records
  86   // the UMA histogram statistics for the current memory pressure level.
  87   void CheckMemoryPressureAndRecordStatistics();
  88
  89   // Get the memory pressure in percent (virtual for testing).
  90   virtual int GetUsedMemoryInPercent();
  91
  92   // The current memory pressure.
  93   base::MemoryPressureListener::MemoryPressureLevel
  94       current_memory_pressure_level_;
  95
  96   // A periodic timer to check for resource pressure changes. This will get
  97   // replaced by a kernel triggered event system (see crbug.com/381196).
  98   base::RepeatingTimer<MemoryPressureMonitor> timer_;
  99
 100   // To slow down the amount of moderate pressure event calls, this counter
 101   // gets used to count the number of events since the last event occured.
 102   int moderate_pressure_repeat_count_;
 103
 104   // The thresholds for moderate and critical pressure.
 105   const int moderate_pressure_threshold_percent_;
 106   const int critical_pressure_threshold_percent_;
 107
 108   // File descriptor used to detect low memory condition.
 109   ScopedFD low_mem_file_;
 110
 111   base::WeakPtrFactory<MemoryPressureMonitor> weak_ptr_factory_;
 112
 113   DISALLOW_COPY_AND_ASSIGN(MemoryPressureMonitor);
 114 };
 115
 116 }  // namespace chromeos
 117 }  // namespace base
 118
 119 #endif  // BASE_MEMORY_MEMORY_PRESSURE_MONITOR_CHROMEOS_H_