Added memory pressure monitor for linux.

base/memory/memory_pressure_monitor_win.h

Index: base/memory/memory_pressure_monitor_win.h
diff --git a/base/memory/memory_pressure_monitor_win.h b/base/memory/memory_pressure_monitor_win.h
deleted file mode 100644
index 07f04eb893ebdb87a736b1daf31f1f93fcb4af05..0000000000000000000000000000000000000000
--- a/base/memory/memory_pressure_monitor_win.h
+++ /dev/null
@@ -1,144 +0,0 @@
-// Copyright 2015 The Chromium Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style license that can be
-// found in the LICENSE file.
-
-#ifndef BASE_MEMORY_MEMORY_PRESSURE_MONITOR_WIN_H_
-#define BASE_MEMORY_MEMORY_PRESSURE_MONITOR_WIN_H_
-
-#include "base/base_export.h"
-#include "base/memory/memory_pressure_listener.h"
-#include "base/memory/memory_pressure_monitor.h"
-#include "base/memory/weak_ptr.h"
-#include "base/threading/thread_checker.h"
-#include "base/timer/timer.h"
-
-// To not pull in windows.h.
-typedef struct _MEMORYSTATUSEX MEMORYSTATUSEX;
-
-namespace base {
-namespace win {
-
-// Windows memory pressure monitor. Because there is no OS provided signal this
-// polls at a low frequency (once per second), and applies internal hysteresis.
-class BASE_EXPORT MemoryPressureMonitor : public base::MemoryPressureMonitor {
- public:
-  // Constants governing the polling and hysteresis behaviour of the observer.
-
-  // The polling interval, in milliseconds. While under critical pressure, this
-  // is also the timer to repeat cleanup attempts.
-  static const int kPollingIntervalMs;
-  // The time which should pass between 2 successive moderate memory pressure
-  // signals, in milliseconds.
-  static const int kModeratePressureCooldownMs;
-  // The number of cycles that should pass between 2 successive moderate memory
-  // pressure signals.
-  static const int kModeratePressureCooldownCycles;
-
-  // Constants governing the memory pressure level detection.
-
-  // The amount of total system memory beyond which a system is considered to be
-  // a large-memory system.
-  static const int kLargeMemoryThresholdMb;
-  // Default minimum free memory thresholds for small-memory systems, in MB.
-  static const int kSmallMemoryDefaultModerateThresholdMb;
-  static const int kSmallMemoryDefaultCriticalThresholdMb;
-  // Default minimum free memory thresholds for large-memory systems, in MB.
-  static const int kLargeMemoryDefaultModerateThresholdMb;
-  static const int kLargeMemoryDefaultCriticalThresholdMb;
-
-  // Default constructor. Will choose thresholds automatically basd on the
-  // actual amount of system memory.
-  MemoryPressureMonitor();
-
-  // Constructor with explicit memory thresholds. These represent the amount of
-  // free memory below which the applicable memory pressure state engages.
-  MemoryPressureMonitor(int moderate_threshold_mb, int critical_threshold_mb);
-
-  ~MemoryPressureMonitor() override;
-
-  // Schedules a memory pressure check to run soon. This must be called on the
-  // same thread where the monitor was instantiated.
-  void CheckMemoryPressureSoon();
-
-  // Get the current memory pressure level. This can be called from any thread.
-  MemoryPressureLevel GetCurrentPressureLevel() const override;
-
-  // Returns the moderate pressure level free memory threshold, in MB.
-  int moderate_threshold_mb() const { return moderate_threshold_mb_; }
-
-  // Returns the critical pressure level free memory threshold, in MB.
-  int critical_threshold_mb() const { return critical_threshold_mb_; }
-
- protected:
-  // Internals are exposed for unittests.
-
-  // Automatically infers threshold values based on system memory. This invokes
-  // GetMemoryStatus so it can be mocked in unittests.
-  void InferThresholds();
-
-  // Starts observing the memory fill level. Calls to StartObserving should
-  // always be matched with calls to StopObserving.
-  void StartObserving();
-
-  // Stop observing the memory fill level. May be safely called if
-  // StartObserving has not been called. Must be called from the same thread on
-  // which the monitor was instantiated.
-  void StopObserving();
-
-  // Checks memory pressure, storing the current level, applying any hysteresis
-  // and emitting memory pressure level change signals as necessary. This
-  // function is called periodically while the monitor is observing memory
-  // pressure. This is split out from CheckMemoryPressureAndRecordStatistics so
-  // that it may be called by CheckMemoryPressureSoon and not invoke UMA
-  // logging. Must be called from the same thread on which the monitor was
-  // instantiated.
-  void CheckMemoryPressure();
-
-  // Wrapper to CheckMemoryPressure that also records the observed memory
-  // pressure level via an UMA enumeration. This is the function that is called
-  // periodically by the timer. Must be called from the same thread on which the
-  // monitor was instantiated.
-  void CheckMemoryPressureAndRecordStatistics();
-
-  // Calculates the current instantaneous memory pressure level. This does not
-  // use any hysteresis and simply returns the result at the current moment. Can
-  // be called on any thread.
-  MemoryPressureLevel CalculateCurrentPressureLevel();
-
-  // Gets system memory status. This is virtual as a unittesting hook. Returns
-  // true if the system call succeeds, false otherwise. Can be called on any
-  // thread.
-  virtual bool GetSystemMemoryStatus(MEMORYSTATUSEX* mem_status);
-
- private:
-  // Threshold amounts of available memory that trigger pressure levels. See
-  // memory_pressure_monitor.cc for a discussion of reasonable values for these.
-  int moderate_threshold_mb_;
-  int critical_threshold_mb_;
-
-  // A periodic timer to check for memory pressure changes.
-  base::RepeatingTimer<MemoryPressureMonitor> timer_;
-
-  // The current memory pressure.
-  MemoryPressureLevel current_memory_pressure_level_;
-
-  // To slow down the amount of moderate pressure event calls, this gets used to
-  // count the number of events since the last event occured. This is used by
-  // |CheckMemoryPressure| to apply hysteresis on the raw results of
-  // |CalculateCurrentPressureLevel|.
-  int moderate_pressure_repeat_count_;
-
-  // Ensures that this object is used from a single thread.
-  base::ThreadChecker thread_checker_;
-
-  // Weak pointer factory to ourself used for scheduling calls to
-  // CheckMemoryPressure/CheckMemoryPressureAndRecordStatistics via |timer_|.
-  base::WeakPtrFactory<MemoryPressureMonitor> weak_ptr_factory_;
-
-  DISALLOW_COPY_AND_ASSIGN(MemoryPressureMonitor);
-};
-
-}  // namespace win
-}  // namespace base
-
-#endif  // BASE_MEMORY_MEMORY_PRESSURE_MONITOR_WIN_H_