vm_pageo.c

open bsd vm device design

/* 
 * Copyright (c) 1991, 1993
 *	The Regents of the University of California.  All rights reserved.
 *
 * This code is derived from software contributed to Berkeley by
 * The Mach Operating System project at Carnegie-Mellon University.
 *
 * 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.
 *
 *	@(#)vm_pageout.c	8.7 (Berkeley) 6/19/95
 *
 *
 * Copyright (c) 1987, 1990 Carnegie-Mellon University.
 * All rights reserved.
 *
 * Authors: Avadis Tevanian, Jr., Michael Wayne Young
 * 
 * Permission to use, copy, modify and distribute this software and
 * its documentation is hereby granted, provided that both the copyright
 * notice and this permission notice appear in all copies of the
 * software, derivative works or modified versions, and any portions
 * thereof, and that both notices appear in supporting documentation.
 * 
 * CARNEGIE MELLON ALLOWS FREE USE OF THIS SOFTWARE IN ITS "AS IS" 
 * CONDITION.  CARNEGIE MELLON DISCLAIMS ANY LIABILITY OF ANY KIND 
 * FOR ANY DAMAGES WHATSOEVER RESULTING FROM THE USE OF THIS SOFTWARE.
 * 
 * Carnegie Mellon requests users of this software to return to
 *
 *  Software Distribution Coordinator  or  [e-mail]
 *  School of Computer Science
 *  Carnegie Mellon University
 *  Pittsburgh PA 15213-3890
 *
 * any improvements or extensions that they make and grant Carnegie the
 * rights to redistribute these changes.
 */

/*
 *	The proverbial page-out daemon.
 */

#include <sys/param.h>

#include <vm/vm.h>
#include <vm/vm_page.h>
#include <vm/vm_pageout.h>

#ifndef VM_PAGE_FREE_MIN
#define VM_PAGE_FREE_MIN	(cnt.v_free_count / 20)
#endif

#ifndef VM_PAGE_FREE_TARGET
#define VM_PAGE_FREE_TARGET	((cnt.v_free_min * 4) / 3)
#endif

int	vm_page_free_min_min = 16 * 1024;
int	vm_page_free_min_max = 256 * 1024;

int	vm_pages_needed;	/* Event on which pageout daemon sleeps */

int	vm_page_max_wired = 0;	/* XXX max # of wired pages system-wide */

#ifdef CLUSTERED_PAGEOUT
#define MAXPOCLUSTER		(MAXPHYS/NBPG)	/* XXX */
int doclustered_pageout = 1;
#endif

/*
 *	vm_pageout_scan does the dirty work for the pageout daemon.
 */
void
vm_pageout_scan()
{
	register vm_page_t	m, next;
	register int		page_shortage;
	register int		s;
	register int		pages_freed;
	int			free;
	vm_object_t		object;

	/*
	 *	Only continue when we want more pages to be "free"
	 */

	cnt.v_rev++;

	s = splimp();
	simple_lock(&vm_page_queue_free_lock);
	free = cnt.v_free_count;
	simple_unlock(&vm_page_queue_free_lock);
	splx(s);

	if (free < cnt.v_free_target) {
		swapout_threads();

		/*
		 *	Be sure the pmap system is updated so
		 *	we can scan the inactive queue.
		 */

		pmap_update();
	}

	/*
	 *	Acquire the resident page system lock,
	 *	as we may be changing what's resident quite a bit.
	 */
	vm_page_lock_queues();

	/*
	 *	Start scanning the inactive queue for pages we can free.
	 *	We keep scanning until we have enough free pages or
	 *	we have scanned through the entire queue.  If we
	 *	encounter dirty pages, we start cleaning them.
	 */

	pages_freed = 0;
	for (m = vm_page_queue_inactive.tqh_first; m != NULL; m = next) {
		s = splimp();
		simple_lock(&vm_page_queue_free_lock);
		free = cnt.v_free_count;
		simple_unlock(&vm_page_queue_free_lock);
		splx(s);
		if (free >= cnt.v_free_target)
			break;

		cnt.v_scan++;
		next = m->pageq.tqe_next;

		/*
		 * If the page has been referenced, move it back to the
		 * active queue.
		 */
		if (pmap_is_referenced(VM_PAGE_TO_PHYS(m))) {
			vm_page_activate(m);
			cnt.v_reactivated++;
			continue;
		}

		/*
		 * If the page is clean, free it up.
		 */
		if (m->flags & PG_CLEAN) {
			object = m->object;
			if (vm_object_lock_try(object)) {
				pmap_page_protect(VM_PAGE_TO_PHYS(m),
						  VM_PROT_NONE);
				vm_page_free(m);
				pages_freed++;
				cnt.v_dfree++;
				vm_object_unlock(object);
			}
			continue;
		}

		/*
		 * If the page is dirty but already being washed, skip it.
		 */
		if ((m->flags & PG_LAUNDRY) == 0)
			continue;

		/*
		 * Otherwise the page is dirty and still in the laundry,
		 * so we start the cleaning operation and remove it from
		 * the laundry.
		 */
		object = m->object;
		if (!vm_object_lock_try(object))
			continue;
		cnt.v_pageouts++;
#ifdef CLUSTERED_PAGEOUT
		if (object->pager &&
		    vm_pager_cancluster(object->pager, PG_CLUSTERPUT))
			vm_pageout_cluster(m, object);
		else
#endif
		vm_pageout_page(m, object);
		thread_wakeup(object);
		vm_object_unlock(object);
		/*
		 * Former next page may no longer even be on the inactive
		 * queue (due to potential blocking in the pager with the
		 * queues unlocked).  If it isn't, we just start over.
		 */
		if (next && (next->flags & PG_INACTIVE) == 0)
			next = vm_page_queue_inactive.tqh_first;
	}
	
	/*
	 *	Compute the page shortage.  If we are still very low on memory
	 *	be sure that we will move a minimal amount of pages from active
	 *	to inactive.
	 */

	page_shortage = cnt.v_inactive_target - cnt.v_inactive_count;
	if (page_shortage <= 0 && pages_freed == 0)
		page_shortage = 1;

	while (page_shortage > 0) {
		/*
		 *	Move some more pages from active to inactive.
		 */

		if ((m = vm_page_queue_active.tqh_first) == NULL)
			break;
		vm_page_deactivate(m);
		page_shortage--;
	}

	vm_page_unlock_queues();
}

/*
 * Called with object and page queues locked.
 * If reactivate is TRUE, a pager error causes the page to be
 * put back on the active queue, ow it is left on the inactive queue.
 */
void
vm_pageout_page(m, object)
	vm_page_t m;
	vm_object_t object;
{
	vm_pager_t pager;
	int pageout_status;

	/*
	 * We set the busy bit to cause potential page faults on
	 * this page to block.
	 *
	 * We also set pageout-in-progress to keep the object from
	 * disappearing during pageout.  This guarantees that the
	 * page won't move from the inactive queue.  (However, any
	 * other page on the inactive queue may move!)
	 */
	pmap_page_protect(VM_PAGE_TO_PHYS(m), VM_PROT_NONE);
	m->flags |= PG_BUSY;

	/*
	 * Try to collapse the object before making a pager for it.
	 * We must unlock the page queues first.
	 */
	vm_page_unlock_queues();
	if (object->pager == NULL)
		vm_object_collapse(object);

	object->paging_in_progress++;
	vm_object_unlock(object);

	/*
	 * Do a wakeup here in case the following operations block.
	 */
	thread_wakeup(&cnt.v_free_count);

	/*
	 * If there is no pager for the page, use the default pager.
	 * If there is no place to put the page at the moment,
	 * leave it in the laundry and hope that there will be
	 * paging space later.
	 */