/*-
 * Copyright (c) 1982, 1986, 1993
 *	The Regents of the University of California.  All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. All advertising materials mentioning features or use of this software
 *    must display the following acknowledgement:
 *	This product includes software developed by the University of
 *	California, Berkeley and its contributors.
 * 4. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 *
 *	@(#)vmmeter.h	8.2 (Berkeley) 7/10/94
 * $FreeBSD: src/sys/sys/vmmeter.h,v 1.21.2.2 2002/10/10 19:28:21 dillon Exp $
 * $DragonFly: src/sys/vm/vm_page2.h,v 1.3 2008/04/14 20:00:29 dillon Exp $
 */

#ifndef _VM_VM_PAGE2_H_
#define _VM_VM_PAGE2_H_

#ifndef _SYS_VMMETER_H_
#include <sys/vmmeter.h>
#endif
#ifndef _SYS_QUEUE_H_
#include <sys/queue.h>
#endif
#ifndef _VM_PAGE_H_
#include <vm/vm_page.h>
#endif

#ifdef _KERNEL

/*
 * Return TRUE if we are under our severe low-free-pages threshold
 *
 * This causes user processes to stall to avoid exhausting memory that
 * the kernel might need.
 *
 * reserved < severe < minimum < target < paging_target
 */
static __inline 
int
vm_page_count_severe(void)
{
    return (vmstats.v_free_severe >
	    vmstats.v_free_count + vmstats.v_cache_count);
}

/*
 * Return TRUE if we are under our minimum low-free-pages threshold.
 * This activates the pageout demon.  The pageout demon tries to
 * reach the target but may stop once it satisfies the minimum.
 *
 * reserved < severe < minimum < target < paging_target
 */
static __inline 
int
vm_page_count_min(int donotcount)
{
    return (vmstats.v_free_min + donotcount >
	    (vmstats.v_free_count + vmstats.v_cache_count) ||
	    vmstats.v_free_reserved > vmstats.v_free_count);
}

/*
 * Return TRUE if we are under our free page target.  The pageout demon
 * tries to reach the target but may stop once it gets past the min.
 */
static __inline 
int
vm_page_count_target(void)
{
    return (vmstats.v_free_target >
	    (vmstats.v_free_count + vmstats.v_cache_count));
}

/*
 * Return the number of pages the pageout daemon needs to move into the
 * cache or free lists.  A negative number means we have sufficient free
 * pages.
 */
static __inline 
int
vm_paging_target(void)
{
    return (
	(vmstats.v_free_target + vmstats.v_cache_min) - 
	(vmstats.v_free_count + vmstats.v_cache_count)
    );
}

/*
 * Return TRUE if we need to start paging.  This routine should not be
 * used to determine when to block on the VM system.  It supplies hysteresis
 * to the pageout code.
 *
 * XXX this triggers a wakeup of the pagedaemon.  As part of its work
 * the pagedaemon tries to maintain v_free_reserved worth of truely
 * free pages.  Set the trigger point a bit lower so we have some hystereis.
 */
static __inline 
int
vm_paging_needed(void)
{
    int trigger;

    trigger = vmstats.v_interrupt_free_min +
	      (vmstats.v_free_reserved - vmstats.v_interrupt_free_min) / 2;
    if (trigger < 10)	/* safety */
	trigger = 10;

    return (
	(vmstats.v_free_min + vmstats.v_cache_min) >
	(vmstats.v_free_count + vmstats.v_cache_count) ||
	trigger > vmstats.v_free_count
    );
}

static __inline
void
vm_page_event(vm_page_t m, vm_page_event_t event)
{
    if (LIST_FIRST(&m->action_list))
	vm_page_event_internal(m, event);
}

static __inline
void
vm_page_init_action(vm_page_action_t action,
		    void (*func)(vm_page_t, vm_page_action_t), void *data)
{
    action->func = func;
    action->data = data;
}

static __inline
void
vm_page_register_action(vm_page_t m, vm_page_action_t action,
			vm_page_event_t event)
{
    action->event = event;
    LIST_INSERT_HEAD(&m->action_list, action, entry);
}

static __inline
void
vm_page_unregister_action(vm_page_t m, vm_page_action_t action)
{
    if (action->event != VMEVENT_NONE) {
	action->event = VMEVENT_NONE;
	LIST_REMOVE(action, entry);
    }
}

#endif	/* _KERNEL */
#endif	/* _VM_VM_PAGE2_H_ */