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1 files changed, 924 insertions, 0 deletions

diff --git a/vm/vm_pageout.c b/vm/vm_pageout.c
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--- /dev/null
+++ b/vm/vm_pageout.c
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+/*
+ * Mach Operating System
+ * Copyright (c) 1991,1990,1989,1988,1987 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:	vm/vm_pageout.c
+ *	Author:	Avadis Tevanian, Jr., Michael Wayne Young
+ *	Date:	1985
+ *
+ *	The proverbial page-out daemon.
+ */
+
+#include <mach_pagemap.h>
+#include <norma_vm.h>
+
+#include <mach/mach_types.h>
+#include <mach/memory_object.h>
+#include "memory_object_default.h"
+#include "memory_object_user.h"
+#include <mach/vm_param.h>
+#include <mach/vm_statistics.h>
+#include <kern/counters.h>
+#include <kern/thread.h>
+#include <vm/pmap.h>
+#include <vm/vm_map.h>
+#include <vm/vm_object.h>
+#include <vm/vm_page.h>
+#include <vm/vm_pageout.h>
+#include <machine/vm_tuning.h>
+
+
+
+#ifndef	VM_PAGEOUT_BURST_MAX
+#define	VM_PAGEOUT_BURST_MAX	10		/* number of pages */
+#endif	VM_PAGEOUT_BURST_MAX
+
+#ifndef	VM_PAGEOUT_BURST_MIN
+#define	VM_PAGEOUT_BURST_MIN	5		/* number of pages */
+#endif	VM_PAGEOUT_BURST_MIN
+
+#ifndef	VM_PAGEOUT_BURST_WAIT
+#define	VM_PAGEOUT_BURST_WAIT	30		/* milliseconds per page */
+#endif	VM_PAGEOUT_BURST_WAIT
+
+#ifndef	VM_PAGEOUT_EMPTY_WAIT
+#define VM_PAGEOUT_EMPTY_WAIT	200		/* milliseconds */
+#endif	VM_PAGEOUT_EMPTY_WAIT
+
+#ifndef	VM_PAGEOUT_PAUSE_MAX
+#define	VM_PAGEOUT_PAUSE_MAX	10		/* number of pauses */
+#endif	VM_PAGEOUT_PAUSE_MAX
+
+/*
+ *	To obtain a reasonable LRU approximation, the inactive queue
+ *	needs to be large enough to give pages on it a chance to be
+ *	referenced a second time.  This macro defines the fraction
+ *	of active+inactive pages that should be inactive.
+ *	The pageout daemon uses it to update vm_page_inactive_target.
+ *
+ *	If vm_page_free_count falls below vm_page_free_target and
+ *	vm_page_inactive_count is below vm_page_inactive_target,
+ *	then the pageout daemon starts running.
+ */
+
+#ifndef	VM_PAGE_INACTIVE_TARGET
+#define	VM_PAGE_INACTIVE_TARGET(avail)	((avail) * 2 / 3)
+#endif	VM_PAGE_INACTIVE_TARGET
+
+/*
+ *	Once the pageout daemon starts running, it keeps going
+ *	until vm_page_free_count meets or exceeds vm_page_free_target.
+ */
+
+#ifndef	VM_PAGE_FREE_TARGET
+#define	VM_PAGE_FREE_TARGET(free)	(15 + (free) / 80)
+#endif	VM_PAGE_FREE_TARGET
+
+/*
+ *	The pageout daemon always starts running once vm_page_free_count
+ *	falls below vm_page_free_min.
+ */
+
+#ifndef	VM_PAGE_FREE_MIN
+#define	VM_PAGE_FREE_MIN(free)	(10 + (free) / 100)
+#endif	VM_PAGE_FREE_MIN
+
+/*
+ *	When vm_page_free_count falls below vm_page_free_reserved,
+ *	only vm-privileged threads can allocate pages.  vm-privilege
+ *	allows the pageout daemon and default pager (and any other
+ *	associated threads needed for default pageout) to continue
+ *	operation by dipping into the reserved pool of pages.
+ */
+
+#ifndef	VM_PAGE_FREE_RESERVED
+#define	VM_PAGE_FREE_RESERVED			15
+#endif	VM_PAGE_FREE_RESERVED
+
+/*
+ *	When vm_page_free_count falls below vm_pageout_reserved_internal,
+ *	the pageout daemon no longer trusts external pagers to clean pages.
+ *	External pagers are probably all wedged waiting for a free page.
+ *	It forcibly double-pages dirty pages belonging to external objects,
+ *	getting the pages to the default pager to clean.
+ */
+
+#ifndef	VM_PAGEOUT_RESERVED_INTERNAL
+#define	VM_PAGEOUT_RESERVED_INTERNAL(reserve)	((reserve) - 5)
+#endif	VM_PAGEOUT_RESERVED_INTERNAL
+
+/*
+ *	When vm_page_free_count falls below vm_pageout_reserved_really,
+ *	the pageout daemon stops work entirely to let the default pager
+ *	catch up (assuming the default pager has pages to clean).
+ *	Beyond this point, it is too dangerous to consume memory
+ *	even for memory_object_data_write messages to the default pager.
+ */
+
+#ifndef	VM_PAGEOUT_RESERVED_REALLY
+#define	VM_PAGEOUT_RESERVED_REALLY(reserve)	((reserve) - 10)
+#endif	VM_PAGEOUT_RESERVED_REALLY
+
+extern void vm_pageout_continue();
+extern void vm_pageout_scan_continue();
+
+unsigned int vm_pageout_reserved_internal = 0;
+unsigned int vm_pageout_reserved_really = 0;
+
+unsigned int vm_pageout_burst_max = 0;
+unsigned int vm_pageout_burst_min = 0;
+unsigned int vm_pageout_burst_wait = 0;		/* milliseconds per page */
+unsigned int vm_pageout_empty_wait = 0;		/* milliseconds */
+unsigned int vm_pageout_pause_count = 0;
+unsigned int vm_pageout_pause_max = 0;
+
+/*
+ *	These variables record the pageout daemon's actions:
+ *	how many pages it looks at and what happens to those pages.
+ *	No locking needed because only one thread modifies the variables.
+ */
+
+unsigned int vm_pageout_active = 0;		/* debugging */
+unsigned int vm_pageout_inactive = 0;		/* debugging */
+unsigned int vm_pageout_inactive_nolock = 0;	/* debugging */
+unsigned int vm_pageout_inactive_busy = 0;	/* debugging */
+unsigned int vm_pageout_inactive_absent = 0;	/* debugging */
+unsigned int vm_pageout_inactive_used = 0;	/* debugging */
+unsigned int vm_pageout_inactive_clean = 0;	/* debugging */
+unsigned int vm_pageout_inactive_dirty = 0;	/* debugging */
+unsigned int vm_pageout_inactive_double = 0;	/* debugging */
+
+#if	NORMA_VM
+/*
+ * Define them here, since they won't be defined by memory_object_user.h.
+ */
+extern kern_return_t memory_object_data_initialize();
+extern kern_return_t memory_object_data_write();
+#endif	NORMA_VM
+
+/*
+ *	Routine:	vm_pageout_setup
+ *	Purpose:
+ *		Set up a page for pageout.
+ *
+ *		Move or copy the page to a new object, as part
+ *		of which it will be sent to its memory manager
+ *		in a memory_object_data_write or memory_object_initialize
+ *		message.
+ *
+ *		The "paging_offset" argument specifies the offset
+ *		of the page within its external memory object.
+ *
+ *		The "new_object" and "new_offset" arguments
+ *		indicate where the page should be moved.
+ *
+ *		The "flush" argument specifies whether the page
+ *		should be flushed from its object.  If not, a
+ *		copy of the page is moved to the new object.
+ *
+ *	In/Out conditions:
+ *		The page in question must not be on any pageout queues,
+ *		and must be busy.  The object to which it belongs
+ *		must be unlocked, and the caller must hold a paging
+ *		reference to it.  The new_object must not be locked.
+ *
+ *		If the page is flushed from its original object,
+ *		this routine returns a pointer to a place-holder page,
+ *		inserted at the same offset, to block out-of-order
+ *		requests for the page.  The place-holder page must
+ *		be freed after the data_write or initialize message
+ *		has been sent.  If the page is copied,
+ *		the holding page is VM_PAGE_NULL.
+ *
+ *		The original page is put on a paging queue and marked
+ *		not busy on exit.
+ */
+vm_page_t
+vm_pageout_setup(m, paging_offset, new_object, new_offset, flush)
+	register vm_page_t	m;
+	vm_offset_t		paging_offset;
+	register vm_object_t	new_object;
+	vm_offset_t		new_offset;
+	boolean_t		flush;
+{
+	register vm_object_t	old_object = m->object;
+	register vm_page_t	holding_page = 0; /*'=0'to quiet gcc warnings*/
+	register vm_page_t	new_m;
+
+	assert(m->busy && !m->absent && !m->fictitious);
+
+	/*
+	 *	If we are not flushing the page, allocate a
+	 *	page in the object.  If we cannot get the
+	 *	page, flush instead.
+	 */
+	if (!flush) {
+		vm_object_lock(new_object);
+		new_m = vm_page_alloc(new_object, new_offset);
+		if (new_m == VM_PAGE_NULL)
+			flush = TRUE;
+		vm_object_unlock(new_object);
+	}
+
+	if (flush) {
+		/*
+		 *	Create a place-holder page where the old one was,
+		 *	to prevent anyone from attempting to page in this
+		 *	page while we`re unlocked.
+		 */
+		while ((holding_page = vm_page_grab_fictitious())
+							== VM_PAGE_NULL)
+			vm_page_more_fictitious();
+
+		vm_object_lock(old_object);
+		vm_page_lock_queues();
+		vm_page_remove(m);
+		vm_page_unlock_queues();
+		PAGE_WAKEUP_DONE(m);
+
+		vm_page_lock_queues();
+		vm_page_insert(holding_page, old_object, m->offset);
+		vm_page_unlock_queues();
+
+		/*
+		 *	Record that this page has been written out
+		 */
+#if	MACH_PAGEMAP
+		vm_external_state_set(old_object->existence_info,
+					paging_offset,
+					VM_EXTERNAL_STATE_EXISTS);
+#endif	MACH_PAGEMAP
+
+		vm_object_unlock(old_object);
+
+		vm_object_lock(new_object);
+
+		/*
+		 *	Move this page into the new object
+		 */
+
+		vm_page_lock_queues();
+		vm_page_insert(m, new_object, new_offset);
+		vm_page_unlock_queues();
+
+		m->dirty = TRUE;
+		m->precious = FALSE;
+		m->page_lock = VM_PROT_NONE;
+		m->unlock_request = VM_PROT_NONE;
+	}
+	else {
+		/*
+		 *	Copy the data into the new page,
+		 *	and mark the new page as clean.
+		 */
+		vm_page_copy(m, new_m);
+
+		vm_object_lock(old_object);
+		m->dirty = FALSE;
+		pmap_clear_modify(m->phys_addr);
+
+		/*
+		 *	Deactivate old page.
+		 */
+		vm_page_lock_queues();
+		vm_page_deactivate(m);
+		vm_page_unlock_queues();
+
+		PAGE_WAKEUP_DONE(m);
+
+		/*
+		 *	Record that this page has been written out
+		 */
+
+#if	MACH_PAGEMAP
+		vm_external_state_set(old_object->existence_info,
+					paging_offset,
+					VM_EXTERNAL_STATE_EXISTS);
+#endif	MACH_PAGEMAP
+
+		vm_object_unlock(old_object);
+
+		vm_object_lock(new_object);
+
+		/*
+		 *	Use the new page below.
+		 */
+		m = new_m;
+		m->dirty = TRUE;
+		assert(!m->precious);
+		PAGE_WAKEUP_DONE(m);
+	}
+
+	/*
+	 *	Make the old page eligible for replacement again; if a
+	 *	user-supplied memory manager fails to release the page,
+	 *	it will be paged out again to the default memory manager.
+	 *
+	 *	Note that pages written to the default memory manager
+	 *	must be wired down -- in return, it guarantees to free
+	 *	this page, rather than reusing it.
+	 */
+
+	vm_page_lock_queues();
+	vm_stat.pageouts++;
+	if (m->laundry) {
+		/*
+		 *	vm_pageout_scan is telling us to put this page
+		 *	at the front of the inactive queue, so it will
+		 *	be immediately paged out to the default pager.
+		 */
+
+		assert(!old_object->internal);
+		m->laundry = FALSE;
+
+		queue_enter_first(&vm_page_queue_inactive, m,
+				  vm_page_t, pageq);
+		m->inactive = TRUE;
+		vm_page_inactive_count++;
+	} else if (old_object->internal) {
+		m->laundry = TRUE;
+		vm_page_laundry_count++;
+
+		vm_page_wire(m);
+	} else
+		vm_page_activate(m);
+	vm_page_unlock_queues();
+
+	/*
+	 *	Since IPC operations may block, we drop locks now.
+	 *	[The placeholder page is busy, and we still have
+	 *	paging_in_progress incremented.]
+	 */
+
+	vm_object_unlock(new_object);
+
+	/*
+	 *	Return the placeholder page to simplify cleanup.
+	 */
+	return (flush ? holding_page : VM_PAGE_NULL);
+}
+
+/*
+ *	Routine:	vm_pageout_page
+ *	Purpose:
+ *		Causes the specified page to be written back to
+ *		the appropriate memory object.
+ *
+ *		The "initial" argument specifies whether this
+ *		data is an initialization only, and should use
+ *		memory_object_data_initialize instead of
+ *		memory_object_data_write.
+ *
+ *		The "flush" argument specifies whether the page
+ *		should be flushed from the object.  If not, a
+ *		copy of the data is sent to the memory object.
+ *
+ *	In/out conditions:
+ *		The page in question must not be on any pageout queues.
+ *		The object to which it belongs must be locked.
+ *	Implementation:
+ *		Move this page to a completely new object, if flushing;
+ *		copy to a new page in a new object, if not.
+ */
+void
+vm_pageout_page(m, initial, flush)
+	register vm_page_t	m;
+	boolean_t		initial;
+	boolean_t		flush;
+{
+	vm_map_copy_t		copy;
+	register vm_object_t	old_object;
+	register vm_object_t	new_object;
+	register vm_page_t	holding_page;
+	vm_offset_t		paging_offset;
+	kern_return_t		rc;
+	boolean_t		precious_clean;
+
+	assert(m->busy);
+
+	/*
+	 *	Cleaning but not flushing a clean precious page is a
+	 *	no-op.  Remember whether page is clean and precious now
+	 *	because vm_pageout_setup will mark it dirty and not precious.
+	 *
+	 * XXX Check if precious_clean && !flush can really happen.
+	 */
+	precious_clean = (!m->dirty) && m->precious;
+	if (precious_clean && !flush) {
+		PAGE_WAKEUP_DONE(m);
+		return;
+	}
+
+	/*
+	 *	Verify that we really want to clean this page.
+	 */
+	if (m->absent || m->error || (!m->dirty && !m->precious)) {
+		VM_PAGE_FREE(m);
+		return;
+	}
+
+	/*
+	 *	Create a paging reference to let us play with the object.
+	 */
+	old_object = m->object;
+	paging_offset = m->offset + old_object->paging_offset;
+	vm_object_paging_begin(old_object);
+	vm_object_unlock(old_object);
+
+	/*
+	 *	Allocate a new object into which we can put the page.
+	 */
+	new_object = vm_object_allocate(PAGE_SIZE);
+
+	/*
+	 *	Move the page into the new object.
+	 */
+	holding_page = vm_pageout_setup(m,
+				paging_offset,
+				new_object,
+				0,		/* new offset */
+				flush);		/* flush */
+
+	rc = vm_map_copyin_object(new_object, 0, PAGE_SIZE, &copy);
+	assert(rc == KERN_SUCCESS);
+
+	if (initial || old_object->use_old_pageout) {
+		rc = (*(initial ? memory_object_data_initialize
+			     : memory_object_data_write))
+			(old_object->pager,
+			 old_object->pager_request,
+			 paging_offset, (pointer_t) copy, PAGE_SIZE);
+	}
+	else {
+		rc = memory_object_data_return(
+			 old_object->pager,
+			 old_object->pager_request,
+			 paging_offset, (pointer_t) copy, PAGE_SIZE,
+			 !precious_clean, !flush);
+	}
+
+	if (rc != KERN_SUCCESS)
+		vm_map_copy_discard(copy);
+
+	/*
+	 *	Clean up.
+	 */
+	vm_object_lock(old_object);
+	if (holding_page != VM_PAGE_NULL)
+	    VM_PAGE_FREE(holding_page);
+	vm_object_paging_end(old_object);
+}
+
+/*
+ *	vm_pageout_scan does the dirty work for the pageout daemon.
+ *	It returns with vm_page_queue_free_lock held and
+ *	vm_page_free_wanted == 0.
+ */
+
+void vm_pageout_scan()
+{
+	unsigned int burst_count;
+
+	/*
+	 *	We want to gradually dribble pages from the active queue
+	 *	to the inactive queue.  If we let the inactive queue get
+	 *	very small, and then suddenly dump many pages into it,
+	 *	those pages won't get a sufficient chance to be referenced
+	 *	before we start taking them from the inactive queue.
+	 *
+	 *	We must limit the rate at which we send pages to the pagers.
+	 *	data_write messages consume memory, for message buffers and
+	 *	for map-copy objects.  If we get too far ahead of the pagers,
+	 *	we can potentially run out of memory.
+	 *
+	 *	We can use the laundry count to limit directly the number
+	 *	of pages outstanding to the default pager.  A similar
+	 *	strategy for external pagers doesn't work, because
+	 *	external pagers don't have to deallocate the pages sent them,
+	 *	and because we might have to send pages to external pagers
+	 *	even if they aren't processing writes.  So we also
+	 *	use a burst count to limit writes to external pagers.
+	 *
+	 *	When memory is very tight, we can't rely on external pagers to
+	 *	clean pages.  They probably aren't running, because they
+	 *	aren't vm-privileged.  If we kept sending dirty pages to them,
+	 *	we could exhaust the free list.  However, we can't just ignore
+	 *	pages belonging to external objects, because there might be no
+	 *	pages belonging to internal objects.  Hence, we get the page
+	 *	into an internal object and then immediately double-page it,
+	 *	sending it to the default pager.
+	 *
+	 *	consider_zone_gc should be last, because the other operations
+	 *	might return memory to zones.  When we pause we use
+	 *	vm_pageout_scan_continue as our continuation, so we will
+	 *	reenter vm_pageout_scan periodically and attempt to reclaim
+	 *	internal memory even if we never reach vm_page_free_target.
+	 */
+
+    Restart:
+	stack_collect();
+	net_kmsg_collect();
+	consider_task_collect();
+	consider_thread_collect();
+	consider_zone_gc();
+
+	for (burst_count = 0;;) {
+		register vm_page_t m;
+		register vm_object_t object;
+		unsigned int free_count;
+
+		/*
+		 *	Recalculate vm_page_inactivate_target.
+		 */
+
+		vm_page_lock_queues();
+		vm_page_inactive_target =
+			VM_PAGE_INACTIVE_TARGET(vm_page_active_count +
+						vm_page_inactive_count);
+
+		/*
+		 *	Move pages from active to inactive.
+		 */
+
+		while ((vm_page_inactive_count < vm_page_inactive_target) &&
+		       !queue_empty(&vm_page_queue_active)) {
+			register vm_object_t obj;
+
+			vm_pageout_active++;
+			m = (vm_page_t) queue_first(&vm_page_queue_active);
+			assert(m->active && !m->inactive);
+
+			obj = m->object;
+			if (!vm_object_lock_try(obj)) {
+				/*
+				 *	Move page to end and continue.
+				 */
+
+				queue_remove(&vm_page_queue_active, m,
+					     vm_page_t, pageq);
+				queue_enter(&vm_page_queue_active, m,
+					    vm_page_t, pageq);
+				vm_page_unlock_queues();
+				vm_page_lock_queues();
+				continue;
+			}
+
+			/*
+			 *	If the page is busy, then we pull it
+			 *	off the active queue and leave it alone.
+			 */
+
+			if (m->busy) {
+				vm_object_unlock(obj);
+				queue_remove(&vm_page_queue_active, m,
+					     vm_page_t, pageq);
+				m->active = FALSE;
+				vm_page_active_count--;
+				continue;
+			}
+
+			/*
+			 *	Deactivate the page while holding the object
+			 *	locked, so we know the page is still not busy.
+			 *	This should prevent races between pmap_enter
+			 *	and pmap_clear_reference.  The page might be
+			 *	absent or fictitious, but vm_page_deactivate
+			 *	can handle that.
+			 */
+
+			vm_page_deactivate(m);
+			vm_object_unlock(obj);
+		}
+
+		/*
+		 *	We are done if we have met our target *and*
+		 *	nobody is still waiting for a page.
+		 */
+
+		simple_lock(&vm_page_queue_free_lock);
+		free_count = vm_page_free_count;
+		if ((free_count >= vm_page_free_target) &
+		    (vm_page_free_wanted == 0)) {
+			vm_page_unlock_queues();
+			break;
+		}
+		simple_unlock(&vm_page_queue_free_lock);
+
+		/*
+		 * Sometimes we have to pause:
+		 *	1) No inactive pages - nothing to do.
+		 *	2) Flow control - wait for pagers to catch up.
+		 *	3) Extremely low memory - sending out dirty pages
+		 *	consumes memory.  We don't take the risk of doing
+		 *	this if the default pager already has work to do.
+		 */
+
+		if (queue_empty(&vm_page_queue_inactive) ||
+		    (burst_count >= vm_pageout_burst_max) ||
+		    (vm_page_laundry_count >= vm_pageout_burst_max) ||
+		    ((free_count < vm_pageout_reserved_really) &&
+		     (vm_page_laundry_count > 0))) {
+			unsigned int pages, msecs;
+
+			/*
+			 *	vm_pageout_burst_wait is msecs/page.
+			 *	If there is nothing for us to do, we wait
+			 *	at least vm_pageout_empty_wait msecs.
+			 */
+
+			if (vm_page_laundry_count > burst_count)
+				pages = vm_page_laundry_count;
+			else
+				pages = burst_count;
+			msecs = pages * vm_pageout_burst_wait;
+
+			if (queue_empty(&vm_page_queue_inactive) &&
+			    (msecs < vm_pageout_empty_wait))
+				msecs = vm_pageout_empty_wait;
+			vm_page_unlock_queues();
+
+			thread_will_wait_with_timeout(current_thread(), msecs);
+			counter(c_vm_pageout_scan_block++);
+			thread_block(vm_pageout_scan_continue);
+#ifndef CONTINUATIONS
+			/*
+			 *	Unfortunately, we don't have call_continuation
+			 *	so we can't rely on tail-recursion.
+			 */
+
+			vm_pageout_scan_continue();
+			goto Restart;
+#else	/* CONTINUATIONS */
+			call_continuation(vm_pageout_scan_continue);
+			/*NOTREACHED*/
+#endif	/* CONTINUATIONS */
+		}
+
+		vm_pageout_inactive++;
+		m = (vm_page_t) queue_first(&vm_page_queue_inactive);
+		assert(!m->active && m->inactive);
+		object = m->object;
+
+		/*
+		 *	Try to lock object; since we've got the
+		 *	page queues lock, we can only try for this one.
+		 */
+
+		if (!vm_object_lock_try(object)) {
+			/*
+			 *	Move page to end and continue.
+			 */
+
+			queue_remove(&vm_page_queue_inactive, m,
+				     vm_page_t, pageq);
+			queue_enter(&vm_page_queue_inactive, m,
+				    vm_page_t, pageq);
+			vm_page_unlock_queues();
+			vm_pageout_inactive_nolock++;
+			continue;
+		}
+
+		/*
+		 *	Remove the page from the inactive list.
+		 */
+
+		queue_remove(&vm_page_queue_inactive, m, vm_page_t, pageq);
+		vm_page_inactive_count--;
+		m->inactive = FALSE;
+
+		if (m->busy || !object->alive) {
+			/*
+			 *	Somebody is already playing with this page.
+			 *	Leave it off the pageout queues.
+			 */
+
+			vm_page_unlock_queues();
+			vm_object_unlock(object);
+			vm_pageout_inactive_busy++;
+			continue;
+		}
+
+		/*
+		 *	If it's absent, we can reclaim the page.
+		 */
+
+		if (m->absent) {
+			vm_pageout_inactive_absent++;
+		    reclaim_page:
+			vm_page_free(m);
+			vm_page_unlock_queues();
+			vm_object_unlock(object);
+			continue;
+		}
+
+		/*
+		 *	If it's being used, reactivate.
+		 *	(Fictitious pages are either busy or absent.)
+		 */
+
+		assert(!m->fictitious);
+		if (m->reference || pmap_is_referenced(m->phys_addr)) {
+			vm_object_unlock(object);
+			vm_page_activate(m);
+			vm_stat.reactivations++;
+			vm_page_unlock_queues();
+			vm_pageout_inactive_used++;
+			continue;
+		}
+
+		/*
+		 *	Eliminate all mappings.
+		 */
+
+		m->busy = TRUE;
+		pmap_page_protect(m->phys_addr, VM_PROT_NONE);
+		if (!m->dirty)
+			m->dirty = pmap_is_modified(m->phys_addr);
+
+		/*
+		 *	If it's clean and not precious, we can free the page.
+		 */
+
+		if (!m->dirty && !m->precious) {
+			vm_pageout_inactive_clean++;
+			goto reclaim_page;
+		}
+
+		/*
+		 *	If we are very low on memory, then we can't
+		 *	rely on an external pager to clean a dirty page,
+		 *	because external pagers are not vm-privileged.
+		 *
+		 *	The laundry bit tells vm_pageout_setup to
+		 *	put the page back at the front of the inactive
+		 *	queue instead of activating the page.  Hence,
+		 *	we will pick the page up again immediately and
+		 *	resend it to the default pager.
+		 */
+
+		assert(!m->laundry);
+		if ((free_count < vm_pageout_reserved_internal) &&
+		    !object->internal) {
+			m->laundry = TRUE;
+			vm_pageout_inactive_double++;
+		}
+		vm_page_unlock_queues();
+
+		/*
+		 *	If there is no memory object for the page, create
+		 *	one and hand it to the default pager.
+		 *	[First try to collapse, so we don't create
+		 *	one unnecessarily.]
+		 */
+
+		if (!object->pager_initialized)
+			vm_object_collapse(object);
+		if (!object->pager_initialized)
+			vm_object_pager_create(object);
+		if (!object->pager_initialized)
+			panic("vm_pageout_scan");
+
+		vm_pageout_inactive_dirty++;
+		vm_pageout_page(m, FALSE, TRUE);	/* flush it */
+		vm_object_unlock(object);
+		burst_count++;
+	}
+}
+
+void vm_pageout_scan_continue()
+{
+	/*
+	 *	We just paused to let the pagers catch up.
+	 *	If vm_page_laundry_count is still high,
+	 *	then we aren't waiting long enough.
+	 *	If we have paused some vm_pageout_pause_max times without
+	 *	adjusting vm_pageout_burst_wait, it might be too big,
+	 *	so we decrease it.
+	 */
+
+	vm_page_lock_queues();
+	if (vm_page_laundry_count > vm_pageout_burst_min) {
+		vm_pageout_burst_wait++;
+		vm_pageout_pause_count = 0;
+	} else if (++vm_pageout_pause_count > vm_pageout_pause_max) {
+		vm_pageout_burst_wait = (vm_pageout_burst_wait * 3) / 4;
+		if (vm_pageout_burst_wait < 1)
+			vm_pageout_burst_wait = 1;
+		vm_pageout_pause_count = 0;
+	}
+	vm_page_unlock_queues();
+
+#ifdef	CONTINUATIONS
+	vm_pageout_continue();
+	/*NOTREACHED*/
+#endif	/* CONTINUATIONS */
+}
+
+/*
+ *	vm_pageout is the high level pageout daemon.
+ */
+
+void vm_pageout_continue()
+{
+	/*
+	 *	The pageout daemon is never done, so loop forever.
+	 *	We should call vm_pageout_scan at least once each
+	 *	time we are woken, even if vm_page_free_wanted is
+	 *	zero, to check vm_page_free_target and
+	 *	vm_page_inactive_target.
+	 */
+
+	for (;;) {
+		vm_pageout_scan();
+		/* we hold vm_page_queue_free_lock now */
+		assert(vm_page_free_wanted == 0);
+
+		assert_wait(&vm_page_free_wanted, FALSE);
+		simple_unlock(&vm_page_queue_free_lock);
+		counter(c_vm_pageout_block++);
+		thread_block(vm_pageout_continue);
+	}
+}
+
+void vm_pageout()
+{
+	int		free_after_reserve;
+
+	current_thread()->vm_privilege = TRUE;
+	stack_privilege(current_thread());
+
+	/*
+	 *	Initialize some paging parameters.
+	 */
+
+	if (vm_pageout_burst_max == 0)
+		vm_pageout_burst_max = VM_PAGEOUT_BURST_MAX;
+
+	if (vm_pageout_burst_min == 0)
+		vm_pageout_burst_min = VM_PAGEOUT_BURST_MIN;
+
+	if (vm_pageout_burst_wait == 0)
+		vm_pageout_burst_wait = VM_PAGEOUT_BURST_WAIT;
+
+	if (vm_pageout_empty_wait == 0)
+		vm_pageout_empty_wait = VM_PAGEOUT_EMPTY_WAIT;
+
+	if (vm_page_free_reserved == 0)
+		vm_page_free_reserved = VM_PAGE_FREE_RESERVED;
+
+	if (vm_pageout_pause_max == 0)
+		vm_pageout_pause_max = VM_PAGEOUT_PAUSE_MAX;
+
+	if (vm_pageout_reserved_internal == 0)
+		vm_pageout_reserved_internal =
+			VM_PAGEOUT_RESERVED_INTERNAL(vm_page_free_reserved);
+
+	if (vm_pageout_reserved_really == 0)
+		vm_pageout_reserved_really =
+			VM_PAGEOUT_RESERVED_REALLY(vm_page_free_reserved);
+
+	free_after_reserve = vm_page_free_count - vm_page_free_reserved;
+
+	if (vm_page_free_min == 0)
+		vm_page_free_min = vm_page_free_reserved +
+			VM_PAGE_FREE_MIN(free_after_reserve);
+
+	if (vm_page_free_target == 0)
+		vm_page_free_target = vm_page_free_reserved +
+			VM_PAGE_FREE_TARGET(free_after_reserve);
+
+	if (vm_page_free_target < vm_page_free_min + 5)
+		vm_page_free_target = vm_page_free_min + 5;
+
+	/*
+	 *	vm_pageout_scan will set vm_page_inactive_target.
+	 */
+
+	vm_pageout_continue();
+	/*NOTREACHED*/
+}