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// Copyright 2017 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.
//
// SwapThrashingMonitor defines a state-based interface for a swap thrashing
// monitor. Thrashing is continuous swap activity, caused by processes needing
// to touch more pages than fit in physical memory, over a given period of time.
//
// The systems interested in observing these signals should query this monitor
// directly, it doesn't offer a notification API. Handling these signals should
// be done carefully in order to not aggravate the problem, in its initial
// implementation this monitor is meant to be used to measure the impact of
// thrashing on the core speed metrics.
//
// The different thrashing states are defined in the
// swap_thrashing_monitor_delegate.h header file.
//
// This monitor is responsible for initiating the observation of the
// swap-thrashing signals and it also enforce the state transition logic, the
// actual swap-thrashing observation logic should be done in a platform-specific
// implementation of the SwapThrashingDelegate class.
#ifndef CHROME_BROWSER_MEMORY_SWAP_THRASHING_MONITOR_H_
#define CHROME_BROWSER_MEMORY_SWAP_THRASHING_MONITOR_H_
#include "base/base_export.h"
#include "base/macros.h"
#include "base/timer/timer.h"
#include "build/build_config.h"
#include "chrome/browser/memory/swap_thrashing_monitor_delegate.h"
namespace memory {
// Class for monitoring the swap-thrashing activity on the system.
//
// It is meant to be used as a singleton by calling the Initialize method,
// e.g.:
// SwapThrashingMonitor::Initialize();
//
// Then the current thrashing level can be obtained by calling
// SwapThrashingMonitor::GetInstance()->GetCurrentSwapThrashingLevel();
//
// This class requires sequence-affinity, through use of ThreadChecker.
class SwapThrashingMonitor {
public:
// Sets the |SwapThrashingMonitor| global instance. This is a no-op if the
// instance has already been initialized.
static void Initialize();
// Returns the |SwapThrashingMonitor| global instance.
static SwapThrashingMonitor* GetInstance();
// Returns the currently observed swap-thrashing pressure.
SwapThrashingLevel GetCurrentSwapThrashingLevel();
protected:
SwapThrashingMonitor();
virtual ~SwapThrashingMonitor();
// Takes fresh measurements from the OS, calculates and stores the level from
// them, and emits metrics if necessary.
void CheckSwapThrashingPressureAndRecordStatistics();
void StartObserving();
private:
// The delegate responsible for measuring the swap-thrashing activity.
std::unique_ptr<SwapThrashingMonitorDelegate> delegate_;
SwapThrashingLevel current_swap_thrashing_level_;
base::RepeatingTimer check_timer_;
SEQUENCE_CHECKER(sequence_checker_);
DISALLOW_COPY_AND_ASSIGN(SwapThrashingMonitor);
};
} // namespace memory
#endif // CHROME_BROWSER_MEMORY_SWAP_THRASHING_MONITOR_H_