freebsd/sys/vm/vm_page.c

/*
 * Copyright (c) 1991 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.
 *
 *	from: @(#)vm_page.c	7.4 (Berkeley) 5/7/91
 *	$Id: vm_page.c,v 1.60 1996/06/26 05:39:25 dyson Exp $
 */

/*
 * 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  Software.Distribution@CS.CMU.EDU
 *  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.
 */

/*
 *	Resident memory management module.
 */
#include "opt_ddb.h"

#include <sys/param.h>
#include <sys/systm.h>
#include <sys/malloc.h>
#include <sys/proc.h>
#include <sys/queue.h>
#include <sys/vmmeter.h>

#include <vm/vm.h>
#include <vm/vm_param.h>
#include <vm/vm_prot.h>
#include <vm/lock.h>
#include <vm/vm_kern.h>
#include <vm/vm_object.h>
#include <vm/vm_page.h>
#include <vm/vm_map.h>
#include <vm/vm_pageout.h>
#include <vm/vm_extern.h>

#ifdef DDB
extern void	DDB_print_page_info __P((void));
#endif

/*
 *	Associated with page of user-allocatable memory is a
 *	page structure.
 */

static struct pglist *vm_page_buckets;	/* Array of buckets */
static int vm_page_bucket_count;	/* How big is array? */
static int vm_page_hash_mask;		/* Mask for hash function */

struct pglist vm_page_queue_free;
struct pglist vm_page_queue_zero;
struct pglist vm_page_queue_active;
struct pglist vm_page_queue_inactive;
struct pglist vm_page_queue_cache;

int no_queue;

struct {
	struct pglist *pl;
	int	*cnt;
} vm_page_queues[PQ_CACHE+1] = {
	{NULL, &no_queue},
	{ &vm_page_queue_free, &cnt.v_free_count},
	{ &vm_page_queue_zero, &cnt.v_free_count},
	{ &vm_page_queue_inactive, &cnt.v_inactive_count},
	{ &vm_page_queue_active, &cnt.v_active_count},
	{ &vm_page_queue_cache, &cnt.v_cache_count}
};

vm_page_t vm_page_array;
static int vm_page_array_size;
long first_page;
static long last_page;
static vm_size_t page_mask;
static int page_shift;
int vm_page_zero_count;

/*
 * map of contiguous valid DEV_BSIZE chunks in a page
 * (this list is valid for page sizes upto 16*DEV_BSIZE)
 */
static u_short vm_page_dev_bsize_chunks[] = {
	0x0, 0x1, 0x3, 0x7, 0xf, 0x1f, 0x3f, 0x7f, 0xff,
	0x1ff, 0x3ff, 0x7ff, 0xfff, 0x1fff, 0x3fff, 0x7fff, 0xffff
};

static inline __pure int
		vm_page_hash __P((vm_object_t object, vm_pindex_t pindex))
		__pure2;

static int vm_page_freechk_and_unqueue __P((vm_page_t m));
static void vm_page_free_wakeup __P((void));

/*
 *	vm_set_page_size:
 *
 *	Sets the page size, perhaps based upon the memory
 *	size.  Must be called before any use of page-size
 *	dependent functions.
 *
 *	Sets page_shift and page_mask from cnt.v_page_size.
 */
void
vm_set_page_size()
{

	if (cnt.v_page_size == 0)
		cnt.v_page_size = DEFAULT_PAGE_SIZE;
	page_mask = cnt.v_page_size - 1;
	if ((page_mask & cnt.v_page_size) != 0)
		panic("vm_set_page_size: page size not a power of two");
	for (page_shift = 0;; page_shift++)
		if ((1 << page_shift) == cnt.v_page_size)
			break;
}

/*
 *	vm_page_startup:
 *
 *	Initializes the resident memory module.
 *
 *	Allocates memory for the page cells, and
 *	for the object/offset-to-page hash table headers.
 *	Each page cell is initialized and placed on the free list.
 */

vm_offset_t
vm_page_startup(starta, enda, vaddr)
	register vm_offset_t starta;
	vm_offset_t enda;
	register vm_offset_t vaddr;
{
	register vm_offset_t mapped;
	register vm_page_t m;
	register struct pglist *bucket;
	vm_size_t npages, page_range;
	register vm_offset_t new_start;
	int i;
	vm_offset_t pa;
	int nblocks;
	vm_offset_t first_managed_page;

	/* the biggest memory array is the second group of pages */
	vm_offset_t start;
	vm_offset_t biggestone, biggestsize;

	vm_offset_t total;

	total = 0;
	biggestsize = 0;
	biggestone = 0;
	nblocks = 0;
	vaddr = round_page(vaddr);

	for (i = 0; phys_avail[i + 1]; i += 2) {
		phys_avail[i] = round_page(phys_avail[i]);
		phys_avail[i + 1] = trunc_page(phys_avail[i + 1]);
	}

	for (i = 0; phys_avail[i + 1]; i += 2) {
		int size = phys_avail[i + 1] - phys_avail[i];

		if (size > biggestsize) {
			biggestone = i;
			biggestsize = size;
		}
		++nblocks;
		total += size;
	}

	start = phys_avail[biggestone];

	/*
	 * Initialize the queue headers for the free queue, the active queue
	 * and the inactive queue.
	 */

	TAILQ_INIT(&vm_page_queue_free);
	TAILQ_INIT(&vm_page_queue_zero);
	TAILQ_INIT(&vm_page_queue_active);
	TAILQ_INIT(&vm_page_queue_inactive);
	TAILQ_INIT(&vm_page_queue_cache);

	/*
	 * Allocate (and initialize) the hash table buckets.
	 *
	 * The number of buckets MUST BE a power of 2, and the actual value is
	 * the next power of 2 greater than the number of physical pages in
	 * the system.
	 *
	 * Note: This computation can be tweaked if desired.
	 */
	vm_page_buckets = (struct pglist *) vaddr;
	bucket = vm_page_buckets;
	if (vm_page_bucket_count == 0) {
		vm_page_bucket_count = 1;
		while (vm_page_bucket_count < atop(total))
			vm_page_bucket_count <<= 1;
	}
	vm_page_hash_mask = vm_page_bucket_count - 1;

	/*
	 * Validate these addresses.
	 */

	new_start = start + vm_page_bucket_count * sizeof(struct pglist);
	new_start = round_page(new_start);
	mapped = vaddr;
	vaddr = pmap_map(mapped, start, new_start,
	    VM_PROT_READ | VM_PROT_WRITE);
	start = new_start;
	bzero((caddr_t) mapped, vaddr - mapped);
	mapped = vaddr;

	for (i = 0; i < vm_page_bucket_count; i++) {
		TAILQ_INIT(bucket);
		bucket++;
	}

	/*
	 * round (or truncate) the addresses to our page size.
	 */

	/*
	 * Pre-allocate maps and map entries that cannot be dynamically
	 * allocated via malloc().  The maps include the kernel_map and
	 * kmem_map which must be initialized before malloc() will work
	 * (obviously).  Also could include pager maps which would be
	 * allocated before kmeminit.
	 *
	 * Allow some kernel map entries... this should be plenty since people
	 * shouldn't be cluttering up the kernel map (they should use their
	 * own maps).
	 */

	kentry_data_size = MAX_KMAP * sizeof(struct vm_map) +
	    MAX_KMAPENT * sizeof(struct vm_map_entry);
	kentry_data_size = round_page(kentry_data_size);
	kentry_data = (vm_offset_t) vaddr;
	vaddr += kentry_data_size;

	/*
	 * Validate these zone addresses.
	 */

	new_start = start + (vaddr - mapped);
	pmap_map(mapped, start, new_start, VM_PROT_READ | VM_PROT_WRITE);
	bzero((caddr_t) mapped, (vaddr - mapped));
	start = round_page(new_start);

	/*
	 * Compute the number of pages of memory that will be available for
	 * use (taking into account the overhead of a page structure per
	 * page).
	 */

	first_page = phys_avail[0] / PAGE_SIZE;
	last_page = phys_avail[(nblocks - 1) * 2 + 1] / PAGE_SIZE;

	page_range = last_page - (phys_avail[0] / PAGE_SIZE);
	npages = (total - (page_range * sizeof(struct vm_page)) -
	    (start - phys_avail[biggestone])) / PAGE_SIZE;

	/*
	 * Initialize the mem entry structures now, and put them in the free
	 * queue.
	 */

	vm_page_array = (vm_page_t) vaddr;
	mapped = vaddr;

	/*
	 * Validate these addresses.
	 */

	new_start = round_page(start + page_range * sizeof(struct vm_page));
	mapped = pmap_map(mapped, start, new_start,
	    VM_PROT_READ | VM_PROT_WRITE);
	start = new_start;

	first_managed_page = start / PAGE_SIZE;

	/*
	 * Clear all of the page structures
	 */
	bzero((caddr_t) vm_page_array, page_range * sizeof(struct vm_page));
	vm_page_array_size = page_range;

	cnt.v_page_count = 0;
	cnt.v_free_count = 0;
	for (i = 0; phys_avail[i + 1] && npages > 0; i += 2) {
		if (i == biggestone)
			pa = ptoa(first_managed_page);
		else
			pa = phys_avail[i];
		while (pa < phys_avail[i + 1] && npages-- > 0) {
			++cnt.v_page_count;
			++cnt.v_free_count;
			m = PHYS_TO_VM_PAGE(pa);
			m->queue = PQ_FREE;
			m->flags = 0;
			m->phys_addr = pa;
			TAILQ_INSERT_TAIL(&vm_page_queue_free, m, pageq);
			pa += PAGE_SIZE;
		}
	}

	return (mapped);
}

/*
 *	vm_page_hash:
 *
 *	Distributes the object/offset key pair among hash buckets.
 *
 *	NOTE:  This macro depends on vm_page_bucket_count being a power of 2.
 */
static inline __pure int
vm_page_hash(object, pindex)
	vm_object_t object;
	vm_pindex_t pindex;
{
	return ((((unsigned) object) >> 5) + (pindex >> 1)) & vm_page_hash_mask;
}

/*
 *	vm_page_insert:		[ internal use only ]
 *
 *	Inserts the given mem entry into the object/object-page
 *	table and object list.
 *
 *	The object and page must be locked, and must be splhigh.
 */

void
vm_page_insert(m, object, pindex)
	register vm_page_t m;
	register vm_object_t object;
	register vm_pindex_t pindex;
{
	register struct pglist *bucket;

	if (m->flags & PG_TABLED)
		panic("vm_page_insert: already inserted");

	/*
	 * Record the object/offset pair in this page
	 */

	m->object = object;
	m->pindex = pindex;

	/*
	 * Insert it into the object_object/offset hash table
	 */

	bucket = &vm_page_buckets[vm_page_hash(object, pindex)];
	TAILQ_INSERT_TAIL(bucket, m, hashq);

	/*
	 * Now link into the object's list of backed pages.
	 */

	TAILQ_INSERT_TAIL(&object->memq, m, listq);
	m->flags |= PG_TABLED;

	/*
	 * And show that the object has one more resident page.
	 */

	object->resident_page_count++;
}

/*
 *	vm_page_remove:		[ internal use only ]
 *				NOTE: used by device pager as well -wfj
 *
 *	Removes the given mem entry from the object/offset-page
 *	table and the object page list.
 *
 *	The object and page must be locked, and at splhigh.
 */

void
vm_page_remove(m)
	register vm_page_t m;
{
	register struct pglist *bucket;

	if (!(m->flags & PG_TABLED))
		return;

	/*
	 * Remove from the object_object/offset hash table
	 */

	bucket = &vm_page_buckets[vm_page_hash(m->object, m->pindex)];
	TAILQ_REMOVE(bucket, m, hashq);

	/*
	 * Now remove from the object's list of backed pages.
	 */

	TAILQ_REMOVE(&m->object->memq, m, listq);

	/*
	 * And show that the object has one fewer resident page.
	 */

	m->object->resident_page_count--;

	m->flags &= ~PG_TABLED;
}

/*
 *	vm_page_lookup:
 *
 *	Returns the page associated with the object/offset
 *	pair specified; if none is found, NULL is returned.
 *
 *	The object must be locked.  No side effects.
 */

vm_page_t
vm_page_lookup(object, pindex)
	register vm_object_t object;
	register vm_pindex_t pindex;
{
	register vm_page_t m;
	register struct pglist *bucket;
	int s;

	/*
	 * Search the hash table for this object/offset pair
	 */

	bucket = &vm_page_buckets[vm_page_hash(object, pindex)];

	s = splvm();
	for (m = TAILQ_FIRST(bucket); m != NULL; m = TAILQ_NEXT(m,hashq)) {
		if ((m->object == object) && (m->pindex == pindex)) {
			splx(s);
			return (m);
		}
	}
	splx(s);
	return (NULL);
}

/*
 *	vm_page_rename:
 *
 *	Move the given memory entry from its
 *	current object to the specified target object/offset.
 *
 *	The object must be locked.
 */
void
vm_page_rename(m, new_object, new_pindex)
	register vm_page_t m;
	register vm_object_t new_object;
	vm_pindex_t new_pindex;
{
	int s;

	s = splvm();
	vm_page_remove(m);
	vm_page_insert(m, new_object, new_pindex);
	splx(s);
}

/*
 * vm_page_unqueue must be called at splhigh();
 */
__inline void
vm_page_unqueue(m, wakeup)
	vm_page_t m;
	int wakeup;
{
	int queue = m->queue;
	if (queue != PQ_NONE) {
		m->queue = PQ_NONE;
		TAILQ_REMOVE(vm_page_queues[queue].pl, m, pageq);
		--(*vm_page_queues[queue].cnt);
		if ((queue == PQ_CACHE) && wakeup) {
			if ((cnt.v_cache_count + cnt.v_free_count) <
				(cnt.v_free_reserved + cnt.v_cache_min))
				pagedaemon_wakeup();
		}
	}
}

/*
 *	vm_page_alloc:
 *
 *	Allocate and return a memory cell associated
 *	with this VM object/offset pair.
 *
 *	page_req classes:
 *	VM_ALLOC_NORMAL		normal process request
 *	VM_ALLOC_SYSTEM		system *really* needs a page
 *	VM_ALLOC_INTERRUPT	interrupt time request
 *	VM_ALLOC_ZERO		zero page
 *
 *	Object must be locked.
 */
vm_page_t
vm_page_alloc(object, pindex, page_req)
	vm_object_t object;
	vm_pindex_t pindex;
	int page_req;
{
	register vm_page_t m;
	int queue;
	int s;

#ifdef DIAGNOSTIC
	m = vm_page_lookup(object, pindex);
	if (m)
		panic("vm_page_alloc: page already allocated");
#endif

	if ((curproc == pageproc) && (page_req != VM_ALLOC_INTERRUPT)) {
		page_req = VM_ALLOC_SYSTEM;
	};

	s = splvm();

	switch (page_req) {

	case VM_ALLOC_NORMAL:
		if (cnt.v_free_count >= cnt.v_free_reserved) {
			m = TAILQ_FIRST(&vm_page_queue_free);
			if (m == NULL) {
				--vm_page_zero_count;
				m = TAILQ_FIRST(&vm_page_queue_zero);
			}
		} else {
			m = TAILQ_FIRST(&vm_page_queue_cache);
			if (m == NULL) {
				splx(s);
#if defined(DIAGNOSTIC)
				if (cnt.v_cache_count > 0)
					printf("vm_page_alloc(NORMAL): missing pages on cache queue: %d\n", cnt.v_cache_count);
#endif
				pagedaemon_wakeup();
				return (NULL);
			}
		}
		break;

	case VM_ALLOC_ZERO:
		if (cnt.v_free_count >= cnt.v_free_reserved) {
			m = TAILQ_FIRST(&vm_page_queue_zero);
			if (m) {
				--vm_page_zero_count;
			} else {
				m = TAILQ_FIRST(&vm_page_queue_free);
			}
		} else {
			m = TAILQ_FIRST(&vm_page_queue_cache);
			if (m == NULL) {
				splx(s);
#if defined(DIAGNOSTIC)
				if (cnt.v_cache_count > 0)
					printf("vm_page_alloc(ZERO): missing pages on cache queue: %d\n", cnt.v_cache_count);
#endif
				pagedaemon_wakeup();
				return (NULL);
			}
		}
		break;

	case VM_ALLOC_SYSTEM:
		if ((cnt.v_free_count >= cnt.v_free_reserved) ||
		    ((cnt.v_cache_count == 0) &&
		    (cnt.v_free_count >= cnt.v_interrupt_free_min))) {
				m = TAILQ_FIRST(&vm_page_queue_free);
				if (m == NULL) {
					--vm_page_zero_count;
					m = TAILQ_FIRST(&vm_page_queue_zero);
				}
		} else {
			m = TAILQ_FIRST(&vm_page_queue_cache);
			if (m == NULL) {
				splx(s);
#if defined(DIAGNOSTIC)
				if (cnt.v_cache_count > 0)
					printf("vm_page_alloc(SYSTEM): missing pages on cache queue: %d\n", cnt.v_cache_count);
#endif
				pagedaemon_wakeup();
				return (NULL);
			}
		}
		break;

	case VM_ALLOC_INTERRUPT:
		if (cnt.v_free_count > 0) {
			m = TAILQ_FIRST(&vm_page_queue_free);
			if (m == NULL) {
				--vm_page_zero_count;
				m = TAILQ_FIRST(&vm_page_queue_zero);
			}
		} else {
			splx(s);
			pagedaemon_wakeup();
			return (NULL);
		}
		break;

	default:
		panic("vm_page_alloc: invalid allocation class");
	}

	queue = m->queue;
	TAILQ_REMOVE(vm_page_queues[queue].pl, m, pageq);
	--(*vm_page_queues[queue].cnt);
	if (queue == PQ_ZERO) {
		m->flags = PG_ZERO|PG_BUSY;
	} else if (queue == PQ_CACHE) {
		vm_page_remove(m);
		m->flags = PG_BUSY;
	} else {
		m->flags = PG_BUSY;
	}
	m->wire_count = 0;
	m->hold_count = 0;
	m->act_count = 0;
	m->busy = 0;
	m->valid = 0;
	m->dirty = 0;
	m->queue = PQ_NONE;

	/* XXX before splx until vm_page_insert is safe */
	vm_page_insert(m, object, pindex);

	splx(s);

	/*
	 * Don't wakeup too often - wakeup the pageout daemon when
	 * we would be nearly out of memory.
	 */
	if (((cnt.v_free_count + cnt.v_cache_count) <
		(cnt.v_free_reserved + cnt.v_cache_min)) ||
			(cnt.v_free_count < cnt.v_pageout_free_min))
		pagedaemon_wakeup();

	return (m);
}

/*
 *	vm_page_activate:
 *
 *	Put the specified page on the active list (if appropriate).
 *
 *	The page queues must be locked.
 */
void
vm_page_activate(m)
	register vm_page_t m;
{
	int s;

	s = splvm();
	if (m->queue == PQ_ACTIVE)
		panic("vm_page_activate: already active");

	if (m->queue == PQ_CACHE)
		cnt.v_reactivated++;

	vm_page_unqueue(m, 1);

	if (m->wire_count == 0) {
		TAILQ_INSERT_TAIL(&vm_page_queue_active, m, pageq);
		m->queue = PQ_ACTIVE;
		if (m->act_count < ACT_INIT)
			m->act_count = ACT_INIT;
		cnt.v_active_count++;
	}
	splx(s);
}

/*
 * helper routine for vm_page_free and vm_page_free_zero
 */
__inline static int
vm_page_freechk_and_unqueue(m)
	vm_page_t m;
{
	if (m->busy ||
		(m->flags & PG_BUSY) ||
		(m->queue == PQ_FREE) ||
		(m->hold_count != 0)) {
		printf("vm_page_free: pindex(%ld), busy(%d), PG_BUSY(%d), hold(%d)\n",
			m->pindex, m->busy,
			(m->flags & PG_BUSY) ? 1 : 0, m->hold_count);
		if (m->queue == PQ_FREE)
			panic("vm_page_free: freeing free page");
		else
			panic("vm_page_free: freeing busy page");
	}

	vm_page_remove(m);
	vm_page_unqueue(m,0);
	if ((m->flags & PG_FICTITIOUS) != 0) {
		return 0;
	}
	if (m->wire_count != 0) {
		if (m->wire_count > 1) {
			panic("vm_page_free: invalid wire count (%d), pindex: 0x%x",
				m->wire_count, m->pindex);
		}
		m->wire_count = 0;
		cnt.v_wire_count--;
	}

	return 1;
}

/*
 * helper routine for vm_page_free and vm_page_free_zero
 */
__inline static void
vm_page_free_wakeup()
{
	
/*
 * if pageout daemon needs pages, then tell it that there are
 * some free.
 */
	if (vm_pageout_pages_needed) {
		wakeup(&vm_pageout_pages_needed);
		vm_pageout_pages_needed = 0;
	}
	/*
	 * wakeup processes that are waiting on memory if we hit a
	 * high water mark. And wakeup scheduler process if we have
	 * lots of memory. this process will swapin processes.
	 */
	if (vm_pages_needed &&
		((cnt.v_free_count + cnt.v_cache_count) >= cnt.v_free_min)) {
		wakeup(&cnt.v_free_count);
		vm_pages_needed = 0;
	}
}

/*
 *	vm_page_free:
 *
 *	Returns the given page to the free list,
 *	disassociating it with any VM object.
 *
 *	Object and page must be locked prior to entry.
 */
void
vm_page_free(m)
	register vm_page_t m;
{
	int s;

	s = splvm();

	cnt.v_tfree++;

	if (!vm_page_freechk_and_unqueue(m)) {
		splx(s);
		return;
	}

	m->queue = PQ_FREE;

	/*
	 * If the pageout process is grabbing the page, it is likely
	 * that the page is NOT in the cache.  It is more likely that
	 * the page will be partially in the cache if it is being
	 * explicitly freed.
	 */
	if (curproc == pageproc) {
		TAILQ_INSERT_TAIL(&vm_page_queue_free, m, pageq);
	} else {
		TAILQ_INSERT_HEAD(&vm_page_queue_free, m, pageq);
	}

	cnt.v_free_count++;
	vm_page_free_wakeup();
	splx(s);
}

void
vm_page_free_zero(m)
	register vm_page_t m;
{
	int s;

	s = splvm();

	cnt.v_tfree++;

	if (!vm_page_freechk_and_unqueue(m)) {
		splx(s);
		return;
	}

	m->queue = PQ_ZERO;

	TAILQ_INSERT_HEAD(&vm_page_queue_zero, m, pageq);
	++vm_page_zero_count;
	cnt.v_free_count++;
	vm_page_free_wakeup();
	splx(s);
}

/*
 *	vm_page_wire:
 *
 *	Mark this page as wired down by yet
 *	another map, removing it from paging queues
 *	as necessary.
 *
 *	The page queues must be locked.
 */
void
vm_page_wire(m)
	register vm_page_t m;
{
	int s;

	if (m->wire_count == 0) {
		s = splvm();
		vm_page_unqueue(m,1);
		splx(s);
		cnt.v_wire_count++;
	}
	m->wire_count++;
	m->flags |= PG_MAPPED;
}

/*
 *	vm_page_unwire:
 *
 *	Release one wiring of this page, potentially
 *	enabling it to be paged again.
 *
 *	The page queues must be locked.
 */
void
vm_page_unwire(m)
	register vm_page_t m;
{
	int s;

	s = splvm();

	if (m->wire_count > 0)
		m->wire_count--;
		
	if (m->wire_count == 0) {
		cnt.v_wire_count--;
		TAILQ_INSERT_TAIL(&vm_page_queue_active, m, pageq);
		m->queue = PQ_ACTIVE;
		cnt.v_active_count++;
	}
	splx(s);
}


/*
 *	vm_page_deactivate:
 *
 *	Returns the given page to the inactive list,
 *	indicating that no physical maps have access
 *	to this page.  [Used by the physical mapping system.]
 *
 *	The page queues must be locked.
 */
void
vm_page_deactivate(m)
	register vm_page_t m;
{
	int s;

	/*
	 * Only move active pages -- ignore locked or already inactive ones.
	 *
	 * XXX: sometimes we get pages which aren't wired down or on any queue -
	 * we need to put them on the inactive queue also, otherwise we lose
	 * track of them. Paul Mackerras (paulus@cs.anu.edu.au) 9-Jan-93.
	 */
	if (m->queue == PQ_INACTIVE)
		return;

	s = splvm();
	if (m->wire_count == 0 && m->hold_count == 0) {
		if (m->queue == PQ_CACHE)
			cnt.v_reactivated++;
		vm_page_unqueue(m,1);
		TAILQ_INSERT_TAIL(&vm_page_queue_inactive, m, pageq);
		m->queue = PQ_INACTIVE;
		cnt.v_inactive_count++;
	}
	splx(s);
}

/*
 * vm_page_cache
 *
 * Put the specified page onto the page cache queue (if appropriate).
 */
void
vm_page_cache(m)
	register vm_page_t m;
{
	int s;

	if ((m->flags & PG_BUSY) || m->busy || m->wire_count) {
		printf("vm_page_cache: attempting to cache busy page\n");
		return;
	}
	if (m->queue == PQ_CACHE)
		return;

	vm_page_protect(m, VM_PROT_NONE);
	if (m->dirty != 0) {
		panic("vm_page_cache: caching a dirty page, pindex: %d", m->pindex);
	}
	s = splvm();
	vm_page_unqueue(m,0);
	TAILQ_INSERT_TAIL(&vm_page_queue_cache, m, pageq);
	m->queue = PQ_CACHE;
	cnt.v_cache_count++;
	vm_page_free_wakeup();
	splx(s);
}


/*
 * mapping function for valid bits or for dirty bits in
 * a page
 */
inline int
vm_page_bits(int base, int size)
{
	u_short chunk;

	if ((base == 0) && (size >= PAGE_SIZE))
		return VM_PAGE_BITS_ALL;
	size = (size + DEV_BSIZE - 1) & ~(DEV_BSIZE - 1);
	base = (base % PAGE_SIZE) / DEV_BSIZE;
	chunk = vm_page_dev_bsize_chunks[size / DEV_BSIZE];
	return (chunk << base) & VM_PAGE_BITS_ALL;
}

/*
 * set a page valid and clean
 */
void
vm_page_set_validclean(m, base, size)
	vm_page_t m;
	int base;
	int size;
{
	int pagebits = vm_page_bits(base, size);
	m->valid |= pagebits;
	m->dirty &= ~pagebits;
	if( base == 0 && size == PAGE_SIZE)
		pmap_tc_modified(m);
}

/*
 * set a page (partially) invalid
 */
void
vm_page_set_invalid(m, base, size)
	vm_page_t m;
	int base;
	int size;
{
	int bits;

	m->valid &= ~(bits = vm_page_bits(base, size));
	if (m->valid == 0)
		m->dirty &= ~bits;
}

/*
 * is (partial) page valid?
 */
int
vm_page_is_valid(m, base, size)
	vm_page_t m;
	int base;
	int size;
{
	int bits = vm_page_bits(base, size);

	if (m->valid && ((m->valid & bits) == bits))
		return 1;
	else
		return 0;
}

void
vm_page_test_dirty(m)
	vm_page_t m;
{
	if (m->dirty != VM_PAGE_BITS_ALL)
		pmap_tc_modified(m);
}

/*
 * This interface is for merging with malloc() someday.
 * Even if we never implement compaction so that contiguous allocation
 * works after initialization time, malloc()'s data structures are good
 * for statistics and for allocations of less than a page.
 */
void *
contigmalloc(size, type, flags, low, high, alignment, boundary)
	unsigned long size;	/* should be size_t here and for malloc() */
	int type;
	int flags;
	unsigned long low;
	unsigned long high;
	unsigned long alignment;
	unsigned long boundary;
{
	int i, s, start;
	vm_offset_t addr, phys, tmp_addr;
	vm_page_t pga = vm_page_array;

	size = round_page(size);
	if (size == 0)
		panic("vm_page_alloc_contig: size must not be 0");
	if ((alignment & (alignment - 1)) != 0)
		panic("vm_page_alloc_contig: alignment must be a power of 2");
	if ((boundary & (boundary - 1)) != 0)
		panic("vm_page_alloc_contig: boundary must be a power of 2");

	start = 0;
	s = splvm();
again:
	/*
	 * Find first page in array that is free, within range, aligned, and
	 * such that the boundary won't be crossed.
	 */
	for (i = start; i < cnt.v_page_count; i++) {
		phys = VM_PAGE_TO_PHYS(&pga[i]);
		if ((pga[i].queue == PQ_FREE) &&
		    (phys >= low) && (phys < high) &&
		    ((phys & (alignment - 1)) == 0) &&
		    (((phys ^ (phys + size - 1)) & ~(boundary - 1)) == 0))
			break;
	}

	/*
	 * If the above failed or we will exceed the upper bound, fail.
	 */
	if ((i == cnt.v_page_count) ||
		((VM_PAGE_TO_PHYS(&pga[i]) + size) > high)) {
		splx(s);
		return (NULL);
	}
	start = i;

	/*
	 * Check successive pages for contiguous and free.
	 */
	for (i = start + 1; i < (start + size / PAGE_SIZE); i++) {
		if ((VM_PAGE_TO_PHYS(&pga[i]) !=
		    (VM_PAGE_TO_PHYS(&pga[i - 1]) + PAGE_SIZE)) ||
		    (pga[i].queue != PQ_FREE)) {
			start++;
			goto again;
		}
	}

	/*
	 * We've found a contiguous chunk that meets are requirements.
	 * Allocate kernel VM, unfree and assign the physical pages to it and
	 * return kernel VM pointer.
	 */
	tmp_addr = addr = kmem_alloc_pageable(kernel_map, size);
	if (addr == 0) {
		splx(s);
		return (NULL);
	}

	for (i = start; i < (start + size / PAGE_SIZE); i++) {
		vm_page_t m = &pga[i];

		TAILQ_REMOVE(&vm_page_queue_free, m, pageq);
		cnt.v_free_count--;
		m->valid = VM_PAGE_BITS_ALL;
		m->flags = 0;
		m->dirty = 0;
		m->wire_count = 0;
		m->busy = 0;
		m->queue = PQ_NONE;
		vm_page_insert(m, kernel_object,
			OFF_TO_IDX(tmp_addr - VM_MIN_KERNEL_ADDRESS));
		vm_page_wire(m);
		pmap_kenter(tmp_addr, VM_PAGE_TO_PHYS(m));
		tmp_addr += PAGE_SIZE;
	}

	splx(s);
	return ((void *)addr);
}

vm_offset_t
vm_page_alloc_contig(size, low, high, alignment)
	vm_offset_t size;
	vm_offset_t low;
	vm_offset_t high;
	vm_offset_t alignment;
{
	return ((vm_offset_t)contigmalloc(size, M_DEVBUF, M_NOWAIT, low, high,
					  alignment, 0ul));
}
#ifdef DDB
void
DDB_print_page_info(void)
{
	printf("cnt.v_free_count: %d\n", cnt.v_free_count);
	printf("cnt.v_cache_count: %d\n", cnt.v_cache_count);
	printf("cnt.v_inactive_count: %d\n", cnt.v_inactive_count);
	printf("cnt.v_active_count: %d\n", cnt.v_active_count);
	printf("cnt.v_wire_count: %d\n", cnt.v_wire_count);
	printf("cnt.v_free_reserved: %d\n", cnt.v_free_reserved);
	printf("cnt.v_free_min: %d\n", cnt.v_free_min);
	printf("cnt.v_free_target: %d\n", cnt.v_free_target);
	printf("cnt.v_cache_min: %d\n", cnt.v_cache_min);
	printf("cnt.v_inactive_target: %d\n", cnt.v_inactive_target);
}
#endif