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/macros.h"
11 #include "base/memory/memory_pressure_listener.h"
12 #include "base/memory/memory_pressure_monitor.h"
13 #include "base/memory/weak_ptr.h"
14 #include "base/timer/timer.h"
15 
16 namespace base {
17 namespace chromeos {
18 
19 class TestMemoryPressureMonitor;
20 
21 ////////////////////////////////////////////////////////////////////////////////
22 // MemoryPressureMonitor
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 MemoryPressureMonitor : public base::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 MemoryPressureMonitor(MemoryPressureThresholds thresholds);
53   ~MemoryPressureMonitor() 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()
62       override;
63   void SetDispatchCallback(const DispatchCallback& callback) 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 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 "Memory.PressureLevel" statistic is recorded every
105   // 5 seconds, but the timer to report "ChromeOS.MemoryPressureLevel"
106   // fires every second. This counter is used to allow reporting
107   // "Memory.PressureLevel" correctly without adding another
108   // timer.
109   int seconds_since_reporting_;
110 
111   // The thresholds for moderate and critical pressure.
112   const int moderate_pressure_threshold_percent_;
113   const int critical_pressure_threshold_percent_;
114 
115   // File descriptor used to detect low memory condition.
116   ScopedFD low_mem_file_;
117 
118   DispatchCallback dispatch_callback_;
119 
120   base::WeakPtrFactory<MemoryPressureMonitor> weak_ptr_factory_;
121 
122   DISALLOW_COPY_AND_ASSIGN(MemoryPressureMonitor);
123 };
124 
125 }  // namespace chromeos
126 }  // namespace base
127 
128 #endif  // BASE_MEMORY_MEMORY_PRESSURE_MONITOR_CHROMEOS_H_
129