Remove memory_pressure component.

components/memory_pressure/direct_memory_pressure_calculator_linux.h

-// Copyright 2016 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 COMPONENTS_MEMORY_PRESSURE_DIRECT_MEMORY_PRESSURE_CALCULATOR_LINUX_H_
-#define COMPONENTS_MEMORY_PRESSURE_DIRECT_MEMORY_PRESSURE_CALCULATOR_LINUX_H_
-
-#include "base/macros.h"
-#include "base/process/process_metrics.h"
-#include "components/memory_pressure/memory_pressure_calculator.h"
-
-namespace base {
-class TimeDelta;
-}
-
-namespace memory_pressure {
-
-// OS-specific implementation of MemoryPressureCalculator. This is only defined
-// and used on platforms that do not have native memory pressure signals
-// (ChromeOS, Linux, Windows). OSes that do have native signals simply hook into
-// the appropriate subsystem (Android, Mac OS X).
-class DirectMemoryPressureCalculator : public MemoryPressureCalculator {
- public:
-  // Exposed for unittesting. See .cc file for detailed discussion of these
-  // constants.
-  static const int kDefaultModerateThresholdPc;
-  static const int kDefaultCriticalThresholdPc;
-
-  // Default constructor. Will choose thresholds automatically based on the
-  // actual amount of system memory installed.
-  DirectMemoryPressureCalculator();
-
-  // Constructor with explicit memory thresholds. These represent the amount of
-  // free memory below which the applicable memory pressure state applies.
-  DirectMemoryPressureCalculator(int moderate_threshold_mb,
-                                 int critical_threshold_mb);
-
-  ~DirectMemoryPressureCalculator() override {}
-
-  // Calculates the current pressure level.
-  MemoryPressureLevel CalculateCurrentPressureLevel() override;
-
-  int moderate_threshold_mb() const { return moderate_threshold_mb_; }
-  int critical_threshold_mb() const { return critical_threshold_mb_; }
-
- private:
-  friend class TestDirectMemoryPressureCalculator;
-
-  MemoryPressureLevel PressureCausedByThrashing(
-      const base::SystemMemoryInfoKB& mem_info);
-  MemoryPressureLevel PressureCausedByOOM(
-      const base::SystemMemoryInfoKB& mem_info);
-
-  // Gets system memory status. This is virtual as a unittesting hook and by
-  // default this invokes base::GetSystemMemoryInfo.
-  virtual bool GetSystemMemoryInfo(base::SystemMemoryInfoKB* mem_info) const;
-
-  // We use CPU time instead of real time because this eliminates the variable
-  // of average system load.  Consumer machines are idle most of the time, so if
-  // we used real time, the average faults/sec would be very low.  As soon as
-  // the user loads anything, the instantaneous faults/sec would increase, and
-  // we would overreport the memory pressure.
-  //
-  // We also ignore system time because we don't want to include the time the OS
-  // takes to swap pages in/out on behalf of processes.
-  //
-  // Virtual as a unittesting hook.
-  virtual base::TimeDelta GetUserCpuTimeSinceBoot() const;
-
-  // Uses GetSystemMemoryInfo to automatically infer appropriate values for
-  // moderate_threshold_mb_ and critical_threshold_mb_.
-  void InferThresholds();
-
-  // Initialize the page fault monitor state so CalculateCurrentPressureLevel
-  // will have a delta to analyze.
-  virtual void InitPageFaultMonitor();
-
-  // Computes last_major_page_faults_/last_user_exec_time_ with some
-  // protection.
-  double AverageFaultsPerSecond() const;
-
-  // Threshold amounts of available memory that trigger pressure levels. See
-  // memory_pressure_monitor_win.cc for a discussion of reasonable values for
-  // these.
-  int moderate_threshold_mb_;
-  int critical_threshold_mb_;
-
-  // State needed by the hard page fault monitor.  These values are assumed
-  // not to overflow.
-  base::TimeDelta last_user_exec_time_;
-  uint64_t last_major_page_faults_;
-  // An exponentially weighted moving average of the sampled faults/sec.
-  double current_faults_per_second_;
-
-  double low_pass_half_life_seconds_;
-
-  // |current_faults_per_second_| must be at least |kModerateMultiplier| *
-  // AverageFaultsPerSecond() to report moderate pressure, and similarly for
-  // critical pressure.  Non-const members for unit testing.
-  //
-  // TODO(thomasanderson): Experimentally determine the correct value for these
-  // constants.
-  double moderate_multiplier_ = 5.0;
-  double critical_multiplier_ = 10.0;
-
-  DISALLOW_COPY_AND_ASSIGN(DirectMemoryPressureCalculator);
-};
-
-}  // namespace memory_pressure
-
-#endif  // COMPONENTS_MEMORY_PRESSURE_DIRECT_MEMORY_PRESSURE_CALCULATOR_LINUX_H_