MemoryPressureManager.h

/*
 * Copyright (c) 2008-2014, Pedigree Developers
 *
 * Please see the CONTRIB file in the root of the source tree for a full
 * list of contributors.
 *
 * Permission to use, copy, modify, and distribute this software for any
 * purpose with or without fee is hereby granted, provided that the above
 * copyright notice and this permission notice appear in all copies.
 *
 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
 * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 */
 
#ifndef MEMORY_PRESSURE_MANAGER_H
#define MEMORY_PRESSURE_MANAGER_H
#include "pedigree/kernel/Atomic.h"
#include "pedigree/kernel/Spinlock.h"
#include "pedigree/kernel/compiler.h"
#include "pedigree/kernel/process/WaitQueue.h"
#include "pedigree/kernel/processor/types.h"
#include "pedigree/kernel/utilities/new"
 
#include <config.h>
 
#define MAX_MEMPRESSURE_PRIORITY 16
 
class EXPORTED_PUBLIC MemoryPressureHandler {
 public:
  MemoryPressureHandler();
  virtual ~MemoryPressureHandler();
 
  virtual const char* getMemoryPressureDescription() = 0;
 
  virtual bool compact() = 0;
 
 private:
  friend class MemoryPressureManager;
 
  MemoryPressureHandler* m_pPrevious;
  MemoryPressureHandler* m_pNext;
  size_t m_Priority;
  size_t m_RegistrationSequence;
  bool m_bRegistered;
  bool m_bRemoving;
 
#if THREADS
  size_t m_CallbacksInFlight;
  const void* m_pCallbackOwner;
  WaitQueue m_CallbackWaiters;
#endif
};
 
class EXPORTED_PUBLIC MemoryPressureManager {
 public:
  MemoryPressureManager();
  ~MemoryPressureManager();
 
  const static size_t HighestPriority = 0;
  const static size_t HighPriority = MAX_MEMPRESSURE_PRIORITY / 3;
  const static size_t MediumPriority = MAX_MEMPRESSURE_PRIORITY / 2;
  const static size_t LowPriority = (MAX_MEMPRESSURE_PRIORITY * 2) / 3;
  const static size_t LowestPriority = MAX_MEMPRESSURE_PRIORITY - 1;
 
  static MemoryPressureManager& instance() {
    return m_Instance;
  }
 
  static size_t getHighWatermark() {
    // Once the system has only this or less pages free, we begin
    // doing compacts. We do not want to wait until the system is
    // actually out of memory, as some compact mechanisms require
    // allocating memory.
    return 16;
  }
 
  static size_t getLowWatermark() {
    // Caches can begin voluntarily evicting cache pages at this mark.
    // Should no action be taken, the system will take over forcefully
    // at the high water mark.
    return 32;
  }
 
  bool compact();
 
  bool compactingForCurrentExecution() const;
 
  void registerHandler(size_t prio, MemoryPressureHandler* pHandler);
 
  void removeHandler(MemoryPressureHandler* pHandler);
 
 private:
  static MemoryPressureManager m_Instance;
 
  Spinlock m_Lock;
  MemoryPressureHandler* m_Handlers[MAX_MEMPRESSURE_PRIORITY];
  MemoryPressureHandler* m_HandlerTails[MAX_MEMPRESSURE_PRIORITY];
  size_t m_NextRegistrationSequence;
  Atomic<bool> m_bCompacting;
  const void* m_pCompactOwner;
#if THREADS
  WaitQueue m_CompactWaiters;
#endif
};
 
#endif