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