path: root/kern/zalloc.c

/*
 * Mach Operating System
 * Copyright (c) 1993-1987 Carnegie Mellon University.
 * Copyright (c) 1993,1994 The University of Utah and
 * the Computer Systems Laboratory (CSL).
 * All rights reserved.
 *
 * 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, THE UNIVERSITY OF UTAH AND CSL ALLOW FREE USE OF
 * THIS SOFTWARE IN ITS "AS IS" CONDITION, AND DISCLAIM 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 Mellon
 * the rights to redistribute these changes.
 */
/*
 *	File:	kern/zalloc.c
 *	Author:	Avadis Tevanian, Jr.
 *
 *	Zone-based memory allocator.  A zone is a collection of fixed size
 *	data blocks for which quick allocation/deallocation is possible.
 */

#include <string.h>

#include <kern/debug.h>
#include <kern/macro_help.h>
#include <kern/printf.h>
#include <kern/mach_clock.h>
#include <kern/sched.h>
#include <kern/zalloc.h>
#include <mach/vm_param.h>
#include <vm/vm_kern.h>
#include <machine/machspl.h>

#if	MACH_DEBUG
#include <mach/kern_return.h>
#include <mach/machine/vm_types.h>
#include <mach_debug/zone_info.h>
#include <kern/host.h>
#include <vm/vm_map.h>
#include <vm/vm_user.h>
#include <vm/vm_kern.h>
#endif

#define ADD_TO_ZONE(zone, element)					\
MACRO_BEGIN								\
		*((vm_offset_t *)(element)) = (zone)->free_elements;	\
		(zone)->free_elements = (vm_offset_t) (element);	\
		zone_count_down(zone);					\
MACRO_END

#define REMOVE_FROM_ZONE(zone, ret, type)				\
MACRO_BEGIN								\
	(ret) = (type) (zone)->free_elements;				\
	if ((ret) != (type) 0) {					\
		zone_count_up(zone);					\
		(zone)->free_elements = *((vm_offset_t *)(ret));	\
	}								\
MACRO_END

#define ALIGN_SIZE_UP(size, align) \
((size) = (((size) + ((align) - 1)) & ~((align) - 1)))

/*
 * Support for garbage collection of unused zone pages:
 */

struct zone_page_table_entry {
	struct	zone_page_table_entry	*next;
	short 	in_free_list;
	short	alloc_count;
};

extern struct zone_page_table_entry * zone_page_table;
extern vm_offset_t zone_map_min_address;

#define lock_zone_page_table() simple_lock(&zone_page_table_lock)
#define unlock_zone_page_table() simple_unlock(&zone_page_table_lock)

#define	zone_page(addr) \
    (&(zone_page_table[(atop(((vm_offset_t)addr) - zone_map_min_address))]))


extern void		zone_page_alloc(vm_offset_t, vm_size_t);
extern void		zone_page_dealloc(vm_offset_t, vm_size_t);
extern void		zone_page_in_use(vm_offset_t, vm_size_t);
extern void		zone_page_free(vm_offset_t, vm_size_t);

zone_t		zone_zone;	/* this is the zone containing other zones */

boolean_t	zone_ignore_overflow = TRUE;

vm_map_t	zone_map = VM_MAP_NULL;
vm_size_t	zone_map_size = 64 * 1024 * 1024;

/*
 *	The VM system gives us an initial chunk of memory.
 *	It has to be big enough to allocate the zone_zone
 *	and some initial kernel data structures, like kernel maps.
 *	It is advantageous to make it bigger than really necessary,
 *	because this memory is more efficient than normal kernel
 *	virtual memory.  (It doesn't have vm_page structures backing it
 *	and it may have other machine-dependent advantages.)
 *	So for best performance, zdata_size should approximate
 *	the amount of memory you expect the zone system to consume.
 */

vm_offset_t	zdata;
vm_size_t	zdata_size = 420 * 1024;

#define zone_lock(zone)					\
MACRO_BEGIN						\
	if (zone->type & ZONE_PAGEABLE) {		\
		lock_write(&zone->complex_lock);	\
	} else {					\
		simple_lock(&zone->lock);		\
	}						\
MACRO_END

#define zone_unlock(zone)				\
MACRO_BEGIN						\
	if (zone->type & ZONE_PAGEABLE) {		\
		lock_done(&zone->complex_lock);		\
	} else {					\
		simple_unlock(&zone->lock);		\
	}						\
MACRO_END

#define zone_lock_init(zone)				\
MACRO_BEGIN						\
	if (zone->type & ZONE_PAGEABLE) {		\
		lock_init(&zone->complex_lock, TRUE);	\
	} else {					\
		simple_lock_init(&zone->lock);		\
	}						\
MACRO_END

static vm_offset_t zget_space(vm_offset_t size, vm_size_t align);

decl_simple_lock_data(,zget_space_lock)
vm_offset_t zalloc_next_space;
vm_offset_t zalloc_end_of_space;
vm_size_t zalloc_wasted_space;

/*
 *	Garbage collection map information
 */
decl_simple_lock_data(,zone_page_table_lock)
struct zone_page_table_entry *	zone_page_table;
vm_offset_t			zone_map_min_address;
vm_offset_t			zone_map_max_address;
int				zone_pages;

extern void zone_page_init(vm_offset_t, vm_size_t, int);

#define	ZONE_PAGE_USED  0
#define ZONE_PAGE_UNUSED -1


/*
 *	Protects first_zone, last_zone, num_zones,
 *	and the next_zone field of zones.
 */
decl_simple_lock_data(,all_zones_lock)
zone_t			first_zone;
zone_t			*last_zone;
int			num_zones;

/*
 *	zinit initializes a new zone.  The zone data structures themselves
 *	are stored in a zone, which is initially a static structure that
 *	is initialized by zone_init.
 */
zone_t zinit(size, align, max, alloc, memtype, name)
	vm_size_t	size;		/* the size of an element */
	vm_size_t	align;		/* alignment of elements */
	vm_size_t	max;		/* maximum memory to use */
	vm_size_t	alloc;		/* allocation size */
	unsigned int	memtype;	/* flags specifying type of memory */
	char		*name;		/* a name for the zone */
{
	register zone_t		z;

	if (zone_zone == ZONE_NULL)
		z = (zone_t) zget_space(sizeof(struct zone), 0);
	else
		z = (zone_t) zalloc(zone_zone);
	if (z == ZONE_NULL)
		panic("zinit");
 	if (alloc == 0)
		alloc = PAGE_SIZE;

	if (size == 0)
		size = sizeof(z->free_elements);
	/*
	 *	Round off all the parameters appropriately.
	 */

	if ((max = round_page(max)) < (alloc = round_page(alloc)))
		max = alloc;

	if (align > 0) {
		if (PAGE_SIZE % align || align % sizeof(z->free_elements))
			panic("zinit");
		ALIGN_SIZE_UP(size, align);
	}

	z->free_elements = 0;
	z->cur_size = 0;
	z->max_size = max;
	z->elem_size = ((size-1) + sizeof(z->free_elements)) -
			((size-1) % sizeof(z->free_elements));
	z->align = align;

	z->alloc_size = alloc;
	z->type = memtype;
	z->zone_name = name;
#ifdef ZONE_COUNT
	z->count = 0;
#endif
	z->doing_alloc = FALSE;
	zone_lock_init(z);

	/*
	 *	Add the zone to the all-zones list.
	 */

	z->next_zone = ZONE_NULL;
	simple_lock(&all_zones_lock);
	*last_zone = z;
	last_zone = &z->next_zone;
	num_zones++;
	simple_unlock(&all_zones_lock);

	return(z);
}

/*
 *	Cram the given memory into the specified zone.
 */
void zcram(zone_t zone, vm_offset_t newmem, vm_size_t size)
{
	register vm_size_t	elem_size;

	if (newmem == (vm_offset_t) 0) {
		panic("zcram - memory at zero");
	}
	elem_size = zone->elem_size;

	zone_lock(zone);
	while (size >= elem_size) {
		ADD_TO_ZONE(zone, newmem);
		zone_page_alloc(newmem, elem_size);
		zone_count_up(zone);	/* compensate for ADD_TO_ZONE */
		size -= elem_size;
		newmem += elem_size;
		zone->cur_size += elem_size;
	}
	zone_unlock(zone);
}

/*
 * Contiguous space allocator for non-paged zones. Allocates "size" amount
 * of memory from zone_map.
 */

static vm_offset_t zget_space(vm_offset_t size, vm_size_t align)
{
	vm_offset_t	new_space = 0;
	vm_offset_t	result;
	vm_size_t	space_to_add = 0; /*'=0' to quiet gcc warnings */

	simple_lock(&zget_space_lock);
	if (align > 0) {
		assert(align < PAGE_SIZE);
		ALIGN_SIZE_UP(zalloc_next_space, align);
	}

	while ((zalloc_next_space + size) > zalloc_end_of_space) {
		/*
		 *	Add at least one page to allocation area.
		 */

		space_to_add = round_page(size);

		if (new_space == 0) {
			/*
			 *	Memory cannot be wired down while holding
			 *	any locks that the pageout daemon might
			 *	need to free up pages.  [Making the zget_space
			 *	lock a complex lock does not help in this
			 *	regard.]
			 *
			 *	Unlock and allocate memory.  Because several
			 *	threads might try to do this at once, don't
			 *	use the memory before checking for available
			 *	space again.
			 */

			simple_unlock(&zget_space_lock);

			if (kmem_alloc_wired(zone_map,
					     &new_space, space_to_add)
							!= KERN_SUCCESS)
				return(0);
			zone_page_init(new_space, space_to_add,
							ZONE_PAGE_USED);
			simple_lock(&zget_space_lock);
			if (align > 0)
				ALIGN_SIZE_UP(zalloc_next_space, align);
			continue;
		}


		/*
	  	 *	Memory was allocated in a previous iteration.
		 *
		 *	Check whether the new region is contiguous
		 *	with the old one.
		 */

		if (new_space != zalloc_end_of_space) {
			/*
			 *	Throw away the remainder of the
			 *	old space, and start a new one.
			 */
			zalloc_wasted_space +=
				zalloc_end_of_space - zalloc_next_space;
			zalloc_next_space = new_space;
		}

		zalloc_end_of_space = new_space + space_to_add;

		new_space = 0;
	}
	result = zalloc_next_space;
	zalloc_next_space += size;
	simple_unlock(&zget_space_lock);

	if (new_space != 0)
		kmem_free(zone_map, new_space, space_to_add);

	return(result);
}


/*
 *	Initialize the "zone of zones" which uses fixed memory allocated
 *	earlier in memory initialization.  zone_bootstrap is called
 *	before zone_init.
 */
void zone_bootstrap(void)
{
	simple_lock_init(&all_zones_lock);
	first_zone = ZONE_NULL;
	last_zone = &first_zone;
	num_zones = 0;

	simple_lock_init(&zget_space_lock);
	zalloc_next_space = zdata;
	zalloc_end_of_space = zdata + zdata_size;
	zalloc_wasted_space = 0;

	zone_zone = ZONE_NULL;
	zone_zone = zinit(sizeof(struct zone), 0, 128 * sizeof(struct zone),
			  sizeof(struct zone), 0, "zones");
}

void zone_init(void)
{
	vm_offset_t	zone_min;
	vm_offset_t	zone_max;

	vm_size_t	zone_table_size;

	zone_map = kmem_suballoc(kernel_map, &zone_min, &zone_max,
				 zone_map_size, FALSE);

	/*
	 * Setup garbage collection information:
	 */

 	zone_table_size = atop(zone_max - zone_min) *
				sizeof(struct zone_page_table_entry);
	if (kmem_alloc_wired(zone_map, (vm_offset_t *) &zone_page_table,
			     zone_table_size) != KERN_SUCCESS)
		panic("zone_init");
	zone_min = (vm_offset_t)zone_page_table + round_page(zone_table_size);
	zone_pages = atop(zone_max - zone_min);
	zone_map_min_address = zone_min;
	zone_map_max_address = zone_max;
	simple_lock_init(&zone_page_table_lock);
	zone_page_init(zone_min, zone_max - zone_min, ZONE_PAGE_UNUSED);
}


/*
 *	zalloc returns an element from the specified zone.
 */
vm_offset_t zalloc(zone_t zone)
{
	vm_offset_t	addr;

	if (zone == ZONE_NULL)
		panic ("zalloc: null zone");

	check_simple_locks();

	zone_lock(zone);
	REMOVE_FROM_ZONE(zone, addr, vm_offset_t);
	while (addr == 0) {
		/*
 		 *	If nothing was there, try to get more
		 */
		if (zone->doing_alloc) {
			/*
			 *	Someone is allocating memory for this zone.
			 *	Wait for it to show up, then try again.
			 */
			assert_wait((event_t)&zone->doing_alloc, TRUE);
			/* XXX say wakeup needed */
			zone_unlock(zone);
			thread_block((void (*)()) 0);
			zone_lock(zone);
		}
		else {
			if ((zone->cur_size + (zone->type & ZONE_PAGEABLE ?
				zone->alloc_size : zone->elem_size)) >
			    zone->max_size) {
				if (zone->type & ZONE_EXHAUSTIBLE)
					break;
				/*
				 * Printf calls logwakeup, which calls
				 * select_wakeup which will do a zfree
				 * (which tries to take the select_zone
				 * lock... Hang.  Release the lock now
				 * so it can be taken again later.
				 * NOTE: this used to be specific to
				 * the select_zone, but for
				 * cleanliness, we just unlock all
				 * zones before this.
				 */
				if (!(zone->type & ZONE_FIXED)) {
					/*
					 * We're willing to overflow certain
					 * zones, but not without complaining.
					 *
					 * This is best used in conjunction
					 * with the collecatable flag. What we
					 * want is an assurance we can get the
					 * memory back, assuming there's no
					 * leak.
					 */
					zone->max_size += (zone->max_size >> 1);
				} else if (!zone_ignore_overflow) {
					zone_unlock(zone);
					printf("zone \"%s\" empty.\n",
						zone->zone_name);
					panic("zalloc: zone %s exhausted",
					      zone->zone_name);
				}
			}

			if (zone->type & ZONE_PAGEABLE)
				zone->doing_alloc = TRUE;
			zone_unlock(zone);

			if (zone->type & ZONE_PAGEABLE) {
				if (kmem_alloc_pageable(zone_map, &addr,
							zone->alloc_size)
							!= KERN_SUCCESS)
					panic("zalloc: no pageable memory for zone %s",
					      zone->zone_name);
				zcram(zone, addr, zone->alloc_size);
				zone_lock(zone);
				zone->doing_alloc = FALSE;
				/* XXX check before doing this */
				thread_wakeup((event_t)&zone->doing_alloc);

				REMOVE_FROM_ZONE(zone, addr, vm_offset_t);
			} else  if (zone->type & ZONE_COLLECTABLE) {
				if (kmem_alloc_wired(zone_map,
						     &addr, zone->alloc_size)
							!= KERN_SUCCESS)
					panic("zalloc: no wired memory for zone %s",
					      zone->zone_name);
				zone_page_init(addr, zone->alloc_size,
							ZONE_PAGE_USED);
				zcram(zone, addr, zone->alloc_size);
				zone_lock(zone);
				REMOVE_FROM_ZONE(zone, addr, vm_offset_t);
			} else {
				addr = zget_space(zone->elem_size, zone->align);
				if (addr == 0)
					panic("zalloc: no memory for zone %s",
					      zone->zone_name);

				zone_lock(zone);
				zone_count_up(zone);
				zone->cur_size += zone->elem_size;
				zone_unlock(zone);
				zone_page_alloc(addr, zone->elem_size);
				return(addr);
			}
		}
	}

	zone_unlock(zone);
	return(addr);
}


/*
 *	zget returns an element from the specified zone
 *	and immediately returns nothing if there is nothing there.
 *
 *	This form should be used when you can not block (like when
 *	processing an interrupt).
 */
vm_offset_t zget(zone_t zone)
{
	register vm_offset_t	addr;

	if (zone == ZONE_NULL)
		panic ("zalloc: null zone");

	zone_lock(zone);
	REMOVE_FROM_ZONE(zone, addr, vm_offset_t);
	zone_unlock(zone);

	return(addr);
}

boolean_t zone_check = FALSE;

void zfree(zone_t zone, vm_offset_t elem)
{
	zone_lock(zone);
	if (zone_check) {
		vm_offset_t this;

		/* check the zone's consistency */

		for (this = zone->free_elements;
		     this != 0;
		     this = * (vm_offset_t *) this)
			if (this == elem)
				panic("zfree");
	}
	ADD_TO_ZONE(zone, elem);
	zone_unlock(zone);
}

/*
 *  Zone garbage collection subroutines
 *
 *  These routines have in common the modification of entries in the
 *  zone_page_table.  The latter contains one entry for every page
 *  in the zone_map.
 *
 *  For each page table entry in the given range:
 *
 *	zone_page_in_use        - decrements in_free_list
 *	zone_page_free          - increments in_free_list
 *	zone_page_init          - initializes in_free_list and alloc_count
 *	zone_page_alloc         - increments alloc_count
 *	zone_page_dealloc       - decrements alloc_count
 *	zone_add_free_page_list - adds the page to the free list
 *
 *  Two counts are maintained for each page, the in_free_list count and
 *  alloc_count.  The alloc_count is how many zone elements have been
 *  allocated from a page.  (Note that the page could contain elements
 *  that span page boundaries.  The count includes these elements so
 *  one element may be counted in two pages.) In_free_list is a count
 *  of how many zone elements are currently free.  If in_free_list is
 *  equal to alloc_count then the page is eligible for garbage
 *  collection.
 *
 *  Alloc_count and in_free_list are initialized to the correct values
 *  for a particular zone when a page is zcram'ed into a zone.  Subsequent
 *  gets and frees of zone elements will call zone_page_in_use and
 *  zone_page_free which modify the in_free_list count.  When the zones
 *  garbage collector runs it will walk through a zones free element list,
 *  remove the elements that reside on collectable pages, and use
 *  zone_add_free_page_list to create a list of pages to be collected.
 */

void zone_page_in_use(addr, size)
vm_offset_t	addr;
vm_size_t	size;
{
	int i, j;
	if ((addr < zone_map_min_address) ||
	    (addr+size > zone_map_max_address)) return;
	i = atop(addr-zone_map_min_address);
	j = atop((addr+size-1) - zone_map_min_address);
	lock_zone_page_table();
	for (; i <= j; i++) {
		zone_page_table[i].in_free_list--;
	}
	unlock_zone_page_table();
}

void zone_page_free(addr, size)
vm_offset_t	addr;
vm_size_t	size;
{
	int i, j;
	if ((addr < zone_map_min_address) ||
	    (addr+size > zone_map_max_address)) return;
	i = atop(addr-zone_map_min_address);
	j = atop((addr+size-1) - zone_map_min_address);
	lock_zone_page_table();
	for (; i <= j; i++) {
		/* Set in_free_list to (ZONE_PAGE_USED + 1) if
		 * it was previously set to ZONE_PAGE_UNUSED.
		 */
		if (zone_page_table[i].in_free_list == ZONE_PAGE_UNUSED) {
			zone_page_table[i].in_free_list = 1;
		} else {
			zone_page_table[i].in_free_list++;
		}
	}
	unlock_zone_page_table();
}

void zone_page_init(addr, size, value)

vm_offset_t	addr;
vm_size_t	size;
int		value;
{
	int i, j;
	if ((addr < zone_map_min_address) ||
	    (addr+size > zone_map_max_address)) return;
	i = atop(addr-zone_map_min_address);
	j = atop((addr+size-1) - zone_map_min_address);
	lock_zone_page_table();
	for (; i <= j; i++) {
		zone_page_table[i].alloc_count = value;
		zone_page_table[i].in_free_list = 0;
	}
	unlock_zone_page_table();
}

void zone_page_alloc(addr, size)
vm_offset_t	addr;
vm_size_t	size;
{
	int i, j;
	if ((addr < zone_map_min_address) ||
	    (addr+size > zone_map_max_address)) return;
	i = atop(addr-zone_map_min_address);
	j = atop((addr+size-1) - zone_map_min_address);
	lock_zone_page_table();
	for (; i <= j; i++) {
		/* Set alloc_count to (ZONE_PAGE_USED + 1) if
		 * it was previously set to ZONE_PAGE_UNUSED.
		 */
		if (zone_page_table[i].alloc_count == ZONE_PAGE_UNUSED) {
			zone_page_table[i].alloc_count = 1;
		} else {
			zone_page_table[i].alloc_count++;
		}
	}
	unlock_zone_page_table();
}

void zone_page_dealloc(addr, size)
vm_offset_t	addr;
vm_size_t	size;
{
	int i, j;
	if ((addr < zone_map_min_address) ||
	    (addr+size > zone_map_max_address)) return;
	i = atop(addr-zone_map_min_address);
	j = atop((addr+size-1) - zone_map_min_address);
	lock_zone_page_table();
	for (; i <= j; i++) {
		zone_page_table[i].alloc_count--;
	}
	unlock_zone_page_table();
}

void
zone_add_free_page_list(free_list, addr, size)
	struct zone_page_table_entry	**free_list;
	vm_offset_t	addr;
	vm_size_t	size;
{
	int i, j;
	if ((addr < zone_map_min_address) ||
	    (addr+size > zone_map_max_address)) return;
	i = atop(addr-zone_map_min_address);
	j = atop((addr+size-1) - zone_map_min_address);
	lock_zone_page_table();
	for (; i <= j; i++) {
		if (zone_page_table[i].alloc_count == 0) {
			zone_page_table[i].next = *free_list;
			*free_list = &zone_page_table[i];
			zone_page_table[i].alloc_count  = ZONE_PAGE_UNUSED;
			zone_page_table[i].in_free_list = 0;
		}
	}
	unlock_zone_page_table();
}


/* This is used for walking through a zone's free element list.
 */
struct zone_free_entry {
	struct zone_free_entry * next;
};


/*	Zone garbage collection
 *
 *	zone_gc will walk through all the free elements in all the
 *	zones that are marked collectable looking for reclaimable
 *	pages.  zone_gc is called by consider_zone_gc when the system
 *	begins to run out of memory.
 */
static void zone_gc(void)
{
	int		max_zones;
	zone_t		z;
	int		i;
	register spl_t	s;
	struct zone_page_table_entry	*freep;
	struct zone_page_table_entry	*zone_free_page_list;

	simple_lock(&all_zones_lock);
	max_zones = num_zones;
	z = first_zone;
	simple_unlock(&all_zones_lock);

	zone_free_page_list = (struct zone_page_table_entry *) 0;

	for (i = 0; i < max_zones; i++) {
		struct zone_free_entry * last;
		struct zone_free_entry * elt;
		assert(z != ZONE_NULL);
	/* run this at splhigh so that interupt routines that use zones
	   can not interupt while their zone is locked */
		s=splhigh();
		zone_lock(z);

		if ((z->type & (ZONE_PAGEABLE|ZONE_COLLECTABLE)) == ZONE_COLLECTABLE) {

		    /* Count the free elements in each page.  This loop
		     * requires that all in_free_list entries are zero.
		     */
		    elt = (struct zone_free_entry *)(z->free_elements);
		    while ((elt != (struct zone_free_entry *)0)) {
			   zone_page_free((vm_offset_t)elt, z->elem_size);
			   elt = elt->next;
		    }

		    /* Now determine which elements should be removed
		     * from the free list and, after all the elements
		     * on a page have been removed, add the element's
		     * page to a list of pages to be freed.
		     */
		    elt = (struct zone_free_entry *)(z->free_elements);
		    last = elt;
		    while ((elt != (struct zone_free_entry *)0)) {
			if (((vm_offset_t)elt>=zone_map_min_address)&&
			    ((vm_offset_t)elt<=zone_map_max_address)&&
			    (zone_page(elt)->in_free_list ==
			     zone_page(elt)->alloc_count)) {

			    z->cur_size -= z->elem_size;
			    zone_page_in_use((vm_offset_t)elt, z->elem_size);
			    zone_page_dealloc((vm_offset_t)elt, z->elem_size);
			    if (zone_page(elt)->alloc_count == 0 ||
			      zone_page(elt+(z->elem_size-1))->alloc_count==0) {
				    zone_add_free_page_list(
					    &zone_free_page_list,
					    (vm_offset_t)elt, z->elem_size);
			    }


			    if (elt == last) {
				elt = elt->next;
				z->free_elements =(vm_offset_t)elt;
				last = elt;
			    } else {
				last->next = elt->next;
				elt = elt->next;
			    }
			} else {
			    /* This element is not eligible for collection
			     * so clear in_free_list in preparation for a
			     * subsequent garbage collection pass.
			     */
			    if (((vm_offset_t)elt>=zone_map_min_address)&&
				((vm_offset_t)elt<=zone_map_max_address)) {
				zone_page(elt)->in_free_list = 0;
			    }
			    last = elt;
			    elt = elt->next;
			}
		    }
		}
		zone_unlock(z);
		splx(s);
		simple_lock(&all_zones_lock);
		z = z->next_zone;
		simple_unlock(&all_zones_lock);
	}

	for (freep = zone_free_page_list; freep != 0; freep = freep->next) {
		vm_offset_t	free_addr;

		free_addr = zone_map_min_address +
			PAGE_SIZE * (freep - zone_page_table);

		/* Hack Hack */
		/* Needed to make vm_map_delete's vm_map_clip_end always be
		 * able to get an element without having to call zget_space and
		 * hang because zone_map is already locked by vm_map_delete */

		extern zone_t		vm_map_kentry_zone;	/* zone for kernel entry structures */
		vm_offset_t entry1 = zalloc(vm_map_kentry_zone),
			    entry2 = zalloc(vm_map_kentry_zone);
		zfree(vm_map_kentry_zone, entry1);
		zfree(vm_map_kentry_zone, entry2);

		kmem_free(zone_map, free_addr, PAGE_SIZE);
	}
}

boolean_t zone_gc_allowed = TRUE;
unsigned zone_gc_last_tick = 0;
unsigned zone_gc_max_rate = 0;		/* in ticks */

/*
 *	consider_zone_gc:
 *
 *	Called by the pageout daemon when the system needs more free pages.
 */

void
consider_zone_gc(void)
{
	/*
	 *	By default, don't attempt zone GC more frequently
	 *	than once a second.
	 */

	if (zone_gc_max_rate == 0)
		zone_gc_max_rate = hz;

	if (zone_gc_allowed &&
	    (sched_tick > (zone_gc_last_tick + zone_gc_max_rate))) {
		zone_gc_last_tick = sched_tick;
		zone_gc();
	}
}

#if	MACH_DEBUG
kern_return_t host_zone_info(host, namesp, namesCntp, infop, infoCntp)
	host_t		host;
	zone_name_array_t *namesp;
	unsigned int	*namesCntp;
	zone_info_array_t *infop;
	unsigned int	*infoCntp;
{
	zone_name_t	*names;
	vm_offset_t	names_addr;
	vm_size_t	names_size = 0; /*'=0' to quiet gcc warnings */
	zone_info_t	*info;
	vm_offset_t	info_addr;
	vm_size_t	info_size = 0; /*'=0' to quiet gcc warnings */
	unsigned int	max_zones, i;
	zone_t		z;
	kern_return_t	kr;

	if (host == HOST_NULL)
		return KERN_INVALID_HOST;

	/*
	 *	We assume that zones aren't freed once allocated.
	 *	We won't pick up any zones that are allocated later.
	 */

	simple_lock(&all_zones_lock);
	max_zones = num_zones;
	z = first_zone;
	simple_unlock(&all_zones_lock);

	if (max_zones <= *namesCntp) {
		/* use in-line memory */

		names = *namesp;
	} else {
		names_size = round_page(max_zones * sizeof *names);
		kr = kmem_alloc_pageable(ipc_kernel_map,
					 &names_addr, names_size);
		if (kr != KERN_SUCCESS)
			return kr;

		names = (zone_name_t *) names_addr;
	}

	if (max_zones <= *infoCntp) {
		/* use in-line memory */

		info = *infop;
	} else {
		info_size = round_page(max_zones * sizeof *info);
		kr = kmem_alloc_pageable(ipc_kernel_map,
					 &info_addr, info_size);
		if (kr != KERN_SUCCESS) {
			if (names != *namesp)
				kmem_free(ipc_kernel_map,
					  names_addr, names_size);
			return kr;
		}

		info = (zone_info_t *) info_addr;
	}

	for (i = 0; i < max_zones; i++) {
		zone_name_t *zn = &names[i];
		zone_info_t *zi = &info[i];
		struct zone zcopy;

		assert(z != ZONE_NULL);

		zone_lock(z);
		zcopy = *z;
		zone_unlock(z);

		simple_lock(&all_zones_lock);
		z = z->next_zone;
		simple_unlock(&all_zones_lock);

		/* assuming here the name data is static */
		(void) strncpy(zn->zn_name, zcopy.zone_name,
			       sizeof zn->zn_name);

#ifdef ZONE_COUNT
		zi->zi_count = zcopy.count;
#else
		zi->zi_count = 0;
#endif
		zi->zi_cur_size = zcopy.cur_size;
		zi->zi_max_size = zcopy.max_size;
		zi->zi_elem_size = zcopy.elem_size;
		zi->zi_alloc_size = zcopy.alloc_size;
		zi->zi_pageable = (zcopy.type & ZONE_PAGEABLE) != 0;
		zi->zi_exhaustible = (zcopy.type & ZONE_EXHAUSTIBLE) != 0;
		zi->zi_collectable = (zcopy.type & ZONE_COLLECTABLE) != 0;
	}

	if (names != *namesp) {
		vm_size_t used;
		vm_map_copy_t copy;

		used = max_zones * sizeof *names;

		if (used != names_size)
			memset((char *) (names_addr + used), 0, names_size - used);

		kr = vm_map_copyin(ipc_kernel_map, names_addr, names_size,
				   TRUE, &copy);
		assert(kr == KERN_SUCCESS);

		*namesp = (zone_name_t *) copy;
	}
	*namesCntp = max_zones;

	if (info != *infop) {
		vm_size_t used;
		vm_map_copy_t copy;

		used = max_zones * sizeof *info;

		if (used != info_size)
			memset((char *) (info_addr + used), 0, info_size - used);

		kr = vm_map_copyin(ipc_kernel_map, info_addr, info_size,
				   TRUE, &copy);
		assert(kr == KERN_SUCCESS);

		*infop = (zone_info_t *) copy;
	}
	*infoCntp = max_zones;

	return KERN_SUCCESS;
}
#endif	/* MACH_DEBUG */