Initial source

1 files changed, 971 insertions, 0 deletions

diff --git a/kern/zalloc.c b/kern/zalloc.c
new file mode 100644
index 0000000..a6421cd
--- /dev/null
+++ b/kern/zalloc.c
@@ -0,0 +1,971 @@
+/*
+ * 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 <kern/macro_help.h>
+#include <kern/sched.h>
+#include <kern/time_out.h>
+#include <kern/zalloc.h>
+#include <mach/vm_param.h>
+#include <vm/vm_kern.h>
+#include <machine/machspl.h>
+
+#include <mach_debug.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
+
+/*
+ * 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();
+extern void		zone_page_dealloc();
+extern void		zone_page_in_use();
+extern void		zone_page_free();
+
+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 = 12 * 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();
+
+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();
+
+#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, max, alloc, memtype, name)
+	vm_size_t	size;		/* the size of an element */
+	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));
+	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;
+
+	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->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_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);
+	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);
+			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()
+{
+	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), 128 * sizeof(struct zone),
+			  sizeof(struct zone), 0, "zones");
+}
+
+void zone_init()
+{
+	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");
+				}
+			}
+
+			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");
+				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");
+				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);
+				if (addr == 0)
+					panic("zalloc");
+
+				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() 
+{
+	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);
+		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()
+{
+	/*
+	 *	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)
+			bzero((char *) (names_addr + used), 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)
+			bzero((char *) (info_addr + used), 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