// Copyright 2019 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#ifndef COMPONENTS_MEMORY_PRESSURE_SYSTEM_MEMORY_PRESSURE_EVALUATOR_WIN_H_
#define COMPONENTS_MEMORY_PRESSURE_SYSTEM_MEMORY_PRESSURE_EVALUATOR_WIN_H_
#include "base/functional/callback_forward.h"
#include "base/memory/memory_pressure_listener.h"
#include "base/memory/weak_ptr.h"
#include "base/sequence_checker.h"
#include "base/time/time.h"
#include "base/timer/timer.h"
#include "base/win/scoped_handle.h"
#include "components/memory_pressure/memory_pressure_voter.h"
#include "components/memory_pressure/system_memory_pressure_evaluator.h"
// To not pull in windows.h.
typedef struct _MEMORYSTATUSEX MEMORYSTATUSEX;
namespace memory_pressure {
namespace win {
// Windows memory pressure voter that checks the amount of RAM left at a low
// frequency and applies internal hysteresis.
class SystemMemoryPressureEvaluator
: public memory_pressure::SystemMemoryPressureEvaluator {
public:
using MemoryPressureLevel = base::MemoryPressureListener::MemoryPressureLevel;
// The memory sampling period, currently 5s.
static const base::TimeDelta kMemorySamplingPeriod;
// Constants governing the polling and hysteresis behaviour of the observer.
// The time which should pass between 2 successive moderate memory pressure
// signals, in milliseconds.
static const base::TimeDelta kModeratePressureCooldown;
// 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 based on the
// actual amount of system memory.
explicit SystemMemoryPressureEvaluator(
std::unique_ptr<MemoryPressureVoter> voter);
// Constructor with explicit memory thresholds. These represent the amount of
// free memory below which the applicable memory pressure state engages.
// For testing purposes.
SystemMemoryPressureEvaluator(int moderate_threshold_mb,
int critical_threshold_mb,
std::unique_ptr<MemoryPressureVoter> voter);
~SystemMemoryPressureEvaluator() override;
SystemMemoryPressureEvaluator(const SystemMemoryPressureEvaluator&) = delete;
SystemMemoryPressureEvaluator& operator=(
const SystemMemoryPressureEvaluator&) = delete;
// 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_; }
// Create a nested evaluator that will use the signals provided by the OS to
// detect memory pressure. This evaluator will take ownership of |voter| and
// use it to cast its vote to the monitor.
//
// This evaluator will subscribe to the OS signals via a call to
// CreateMemoryResourceNotification and will use the following mapping:
// - MEMORY_PRESSURE_LEVEL_CRITICAL: LowMemoryResourceNotification.
// - MEMORY_PRESSURE_LEVEL_MODERATE: Not measured by this evaluator.
// - MEMORY_PRESSURE_LEVEL_NONE: HighMemoryResourceNotification.
//
// MEMORY_PRESSURE_LEVEL_CRITICAL signals will be emitted as soon as the low
// memory notification is received and at regular interval until receiving a
// HighMemoryResourceNotification.
void CreateOSSignalPressureEvaluator(
std::unique_ptr<MemoryPressureVoter> voter);
// Testing seams for the OSSignalPressureEvaluator.
void ReplaceWatchedHandleForTesting(base::win::ScopedHandle handle);
void WaitForHighMemoryNotificationForTesting(base::OnceClosure closure);
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. Must be called from the same thread on which the monitor was
// instantiated.
void CheckMemoryPressure();
// 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:
class OSSignalsMemoryPressureEvaluator;
// 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 timer_;
// To slow down the amount of moderate pressure event calls, this gets used to
// count the number of events since the last event occurred. This is used by
// |CheckMemoryPressure| to apply hysteresis on the raw results of
// |CalculateCurrentPressureLevel|.
int moderate_pressure_repeat_count_;
// Optional companion evaluator that will receive the OS memory pressure
// notifications, created by |CreateOSSignalPressureEvaluator|.
std::unique_ptr<OSSignalsMemoryPressureEvaluator> os_signals_evaluator_;
// Ensures that this object is used from a single sequence.
SEQUENCE_CHECKER(sequence_checker_);
// Weak pointer factory to ourself used for scheduling calls to
// CheckMemoryPressure/CheckMemoryPressureAndRecordStatistics via |timer_|.
base::WeakPtrFactory<SystemMemoryPressureEvaluator> weak_ptr_factory_{this};
};
} // namespace win
} // namespace memory_pressure
#endif // COMPONENTS_MEMORY_PRESSURE_SYSTEM_MEMORY_PRESSURE_EVALUATOR_WIN_H_