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freebsd-dev/sys/vm/vm_pageout.c
John Dyson 7e00649986 Improve management of pages moving from the inactive to active queue. Additionally, 
add some much needed comments.
1997-10-06 02:48:16 +00:00

1294 lines
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/*
* Copyright (c) 1991 Regents of the University of California.
* All rights reserved.
* Copyright (c) 1994 John S. Dyson
* All rights reserved.
* Copyright (c) 1994 David Greenman
* 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_pageout.c 7.4 (Berkeley) 5/7/91
*
*
* 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.
*
* $Id: vm_pageout.c,v 1.98 1997/09/01 03:17:26 bde Exp $
*/
/*
* The proverbial page-out daemon.
*/
#include <sys/param.h>
#include <sys/systm.h>
#include <sys/kernel.h>
#include <sys/proc.h>
#include <sys/resourcevar.h>
#include <sys/signalvar.h>
#include <sys/vnode.h>
#include <sys/vmmeter.h>
#include <sys/sysctl.h>
#include <vm/vm.h>
#include <vm/vm_param.h>
#include <vm/vm_prot.h>
#include <sys/lock.h>
#include <vm/vm_object.h>
#include <vm/vm_page.h>
#include <vm/vm_map.h>
#include <vm/vm_pageout.h>
#include <vm/vm_pager.h>
#include <vm/swap_pager.h>
#include <vm/vm_extern.h>
/*
* System initialization
*/
/* the kernel process "vm_pageout"*/
static void vm_pageout __P((void));
static int vm_pageout_clean __P((vm_page_t, int));
static int vm_pageout_scan __P((void));
static int vm_pageout_free_page_calc __P((vm_size_t count));
struct proc *pageproc;
static struct kproc_desc page_kp = {
"pagedaemon",
vm_pageout,
&pageproc
};
SYSINIT_KT(pagedaemon, SI_SUB_KTHREAD_PAGE, SI_ORDER_FIRST, kproc_start, &page_kp)
#if !defined(NO_SWAPPING)
/* the kernel process "vm_daemon"*/
static void vm_daemon __P((void));
static struct proc *vmproc;
static struct kproc_desc vm_kp = {
"vmdaemon",
vm_daemon,
&vmproc
};
SYSINIT_KT(vmdaemon, SI_SUB_KTHREAD_VM, SI_ORDER_FIRST, kproc_start, &vm_kp)
#endif
int vm_pages_needed; /* Event on which pageout daemon sleeps */
int vm_pageout_pages_needed; /* flag saying that the pageout daemon needs pages */
extern int npendingio;
#if !defined(NO_SWAPPING)
static int vm_pageout_req_swapout; /* XXX */
static int vm_daemon_needed;
#endif
extern int nswiodone;
extern int vm_swap_size;
extern int vfs_update_wakeup;
int vm_pageout_stats_max=0, vm_pageout_stats_interval = 0;
int vm_pageout_full_stats_interval = 0;
int vm_pageout_stats_free_max=0, vm_pageout_algorithm_lru=0;
#if defined(NO_SWAPPING)
int vm_swapping_enabled=0;
#else
int vm_swapping_enabled=1;
#endif
SYSCTL_INT(_vm, VM_PAGEOUT_ALGORITHM, pageout_algorithm,
CTLFLAG_RW, &vm_pageout_algorithm_lru, 0, "");
SYSCTL_INT(_vm, OID_AUTO, pageout_stats_max,
CTLFLAG_RW, &vm_pageout_stats_max, 0, "");
SYSCTL_INT(_vm, OID_AUTO, pageout_full_stats_interval,
CTLFLAG_RW, &vm_pageout_full_stats_interval, 0, "");
SYSCTL_INT(_vm, OID_AUTO, pageout_stats_interval,
CTLFLAG_RW, &vm_pageout_stats_interval, 0, "");
SYSCTL_INT(_vm, OID_AUTO, pageout_stats_free_max,
CTLFLAG_RW, &vm_pageout_stats_free_max, 0, "");
#if defined(NO_SWAPPING)
SYSCTL_INT(_vm, VM_SWAPPING_ENABLED, swapping_enabled,
CTLFLAG_RD, &vm_swapping_enabled, 0, "");
#else
SYSCTL_INT(_vm, VM_SWAPPING_ENABLED, swapping_enabled,
CTLFLAG_RW, &vm_swapping_enabled, 0, "");
#endif
#define MAXLAUNDER (cnt.v_page_count > 1800 ? 32 : 16)
#define VM_PAGEOUT_PAGE_COUNT 16
int vm_pageout_page_count = VM_PAGEOUT_PAGE_COUNT;
int vm_page_max_wired; /* XXX max # of wired pages system-wide */
#if !defined(NO_SWAPPING)
typedef void freeer_fcn_t __P((vm_map_t, vm_object_t, vm_pindex_t, int));
static void vm_pageout_map_deactivate_pages __P((vm_map_t, vm_pindex_t));
static freeer_fcn_t vm_pageout_object_deactivate_pages;
static void vm_req_vmdaemon __P((void));
#endif
static void vm_pageout_page_stats(void);
/*
* vm_pageout_clean:
*
* Clean the page and remove it from the laundry.
*
* We set the busy bit to cause potential page faults on this page to
* block.
*
* And we set pageout-in-progress to keep the object from disappearing
* during pageout. This guarantees that the page won't move from the
* inactive queue. (However, any other page on the inactive queue may
* move!)
*/
static int
vm_pageout_clean(m, sync)
vm_page_t m;
int sync;
{
register vm_object_t object;
vm_page_t mc[2*vm_pageout_page_count];
int pageout_count;
int i, forward_okay, backward_okay, page_base;
vm_pindex_t pindex = m->pindex;
object = m->object;
/*
* If not OBJT_SWAP, additional memory may be needed to do the pageout.
* Try to avoid the deadlock.
*/
if ((sync != VM_PAGEOUT_FORCE) &&
(object->type == OBJT_DEFAULT) &&
((cnt.v_free_count + cnt.v_cache_count) < cnt.v_pageout_free_min))
return 0;
/*
* Don't mess with the page if it's busy.
*/
if ((!sync && m->hold_count != 0) ||
((m->busy != 0) || (m->flags & PG_BUSY)))
return 0;
/*
* Try collapsing before it's too late.
*/
if (!sync && object->backing_object) {
vm_object_collapse(object);
}
mc[vm_pageout_page_count] = m;
pageout_count = 1;
page_base = vm_pageout_page_count;
forward_okay = TRUE;
if (pindex != 0)
backward_okay = TRUE;
else
backward_okay = FALSE;
/*
* Scan object for clusterable pages.
*
* We can cluster ONLY if: ->> the page is NOT
* clean, wired, busy, held, or mapped into a
* buffer, and one of the following:
* 1) The page is inactive, or a seldom used
* active page.
* -or-
* 2) we force the issue.
*/
for (i = 1; (i < vm_pageout_page_count) && (forward_okay || backward_okay); i++) {
vm_page_t p;
/*
* See if forward page is clusterable.
*/
if (forward_okay) {
/*
* Stop forward scan at end of object.
*/
if ((pindex + i) > object->size) {
forward_okay = FALSE;
goto do_backward;
}
p = vm_page_lookup(object, pindex + i);
if (p) {
if (((p->queue - p->pc) == PQ_CACHE) ||
(p->flags & PG_BUSY) || p->busy) {
forward_okay = FALSE;
goto do_backward;
}
vm_page_test_dirty(p);
if ((p->dirty & p->valid) != 0 &&
((p->queue == PQ_INACTIVE) ||
(sync == VM_PAGEOUT_FORCE)) &&
(p->wire_count == 0) &&
(p->hold_count == 0)) {
mc[vm_pageout_page_count + i] = p;
pageout_count++;
if (pageout_count == vm_pageout_page_count)
break;
} else {
forward_okay = FALSE;
}
} else {
forward_okay = FALSE;
}
}
do_backward:
/*
* See if backward page is clusterable.
*/
if (backward_okay) {
/*
* Stop backward scan at beginning of object.
*/
if ((pindex - i) == 0) {
backward_okay = FALSE;
}
p = vm_page_lookup(object, pindex - i);
if (p) {
if (((p->queue - p->pc) == PQ_CACHE) ||
(p->flags & PG_BUSY) || p->busy) {
backward_okay = FALSE;
continue;
}
vm_page_test_dirty(p);
if ((p->dirty & p->valid) != 0 &&
((p->queue == PQ_INACTIVE) ||
(sync == VM_PAGEOUT_FORCE)) &&
(p->wire_count == 0) &&
(p->hold_count == 0)) {
mc[vm_pageout_page_count - i] = p;
pageout_count++;
page_base--;
if (pageout_count == vm_pageout_page_count)
break;
} else {
backward_okay = FALSE;
}
} else {
backward_okay = FALSE;
}
}
}
/*
* we allow reads during pageouts...
*/
for (i = page_base; i < (page_base + pageout_count); i++) {
mc[i]->flags |= PG_BUSY;
vm_page_protect(mc[i], VM_PROT_READ);
}
return vm_pageout_flush(&mc[page_base], pageout_count, sync);
}
int
vm_pageout_flush(mc, count, sync)
vm_page_t *mc;
int count;
int sync;
{
register vm_object_t object;
int pageout_status[count];
int anyok = 0;
int i;
object = mc[0]->object;
object->paging_in_progress += count;
vm_pager_put_pages(object, mc, count,
((sync || (object == kernel_object)) ? TRUE : FALSE),
pageout_status);
for (i = 0; i < count; i++) {
vm_page_t mt = mc[i];
switch (pageout_status[i]) {
case VM_PAGER_OK:
++anyok;
break;
case VM_PAGER_PEND:
++anyok;
break;
case VM_PAGER_BAD:
/*
* Page outside of range of object. Right now we
* essentially lose the changes by pretending it
* worked.
*/
pmap_clear_modify(VM_PAGE_TO_PHYS(mt));
mt->dirty = 0;
break;
case VM_PAGER_ERROR:
case VM_PAGER_FAIL:
/*
* If page couldn't be paged out, then reactivate the
* page so it doesn't clog the inactive list. (We
* will try paging out it again later).
*/
if (mt->queue == PQ_INACTIVE)
vm_page_activate(mt);
break;
case VM_PAGER_AGAIN:
break;
}
/*
* If the operation is still going, leave the page busy to
* block all other accesses. Also, leave the paging in
* progress indicator set so that we don't attempt an object
* collapse.
*/
if (pageout_status[i] != VM_PAGER_PEND) {
vm_object_pip_wakeup(object);
PAGE_WAKEUP(mt);
}
}
return anyok;
}
#if !defined(NO_SWAPPING)
/*
* vm_pageout_object_deactivate_pages
*
* deactivate enough pages to satisfy the inactive target
* requirements or if vm_page_proc_limit is set, then
* deactivate all of the pages in the object and its
* backing_objects.
*
* The object and map must be locked.
*/
static void
vm_pageout_object_deactivate_pages(map, object, desired, map_remove_only)
vm_map_t map;
vm_object_t object;
vm_pindex_t desired;
int map_remove_only;
{
register vm_page_t p, next;
int rcount;
int remove_mode;
int s;
if (object->type == OBJT_DEVICE)
return;
while (object) {
if (vm_map_pmap(map)->pm_stats.resident_count <= desired)
return;
if (object->paging_in_progress)
return;
remove_mode = map_remove_only;
if (object->shadow_count > 1)
remove_mode = 1;
/*
* scan the objects entire memory queue
*/
rcount = object->resident_page_count;
p = TAILQ_FIRST(&object->memq);
while (p && (rcount-- > 0)) {
int actcount;
if (vm_map_pmap(map)->pm_stats.resident_count <= desired)
return;
next = TAILQ_NEXT(p, listq);
cnt.v_pdpages++;
if (p->wire_count != 0 ||
p->hold_count != 0 ||
p->busy != 0 ||
(p->flags & PG_BUSY) ||
!pmap_page_exists(vm_map_pmap(map), VM_PAGE_TO_PHYS(p))) {
p = next;
continue;
}
actcount = pmap_ts_referenced(VM_PAGE_TO_PHYS(p));
if (actcount) {
p->flags |= PG_REFERENCED;
} else if (p->flags & PG_REFERENCED) {
actcount = 1;
}
if ((p->queue != PQ_ACTIVE) &&
(p->flags & PG_REFERENCED)) {
vm_page_activate(p);
p->act_count += actcount;
p->flags &= ~PG_REFERENCED;
} else if (p->queue == PQ_ACTIVE) {
if ((p->flags & PG_REFERENCED) == 0) {
p->act_count -= min(p->act_count, ACT_DECLINE);
if (!remove_mode && (vm_pageout_algorithm_lru || (p->act_count == 0))) {
vm_page_protect(p, VM_PROT_NONE);
vm_page_deactivate(p);
} else {
s = splvm();
TAILQ_REMOVE(&vm_page_queue_active, p, pageq);
TAILQ_INSERT_TAIL(&vm_page_queue_active, p, pageq);
splx(s);
}
} else {
p->flags &= ~PG_REFERENCED;
if (p->act_count < (ACT_MAX - ACT_ADVANCE))
p->act_count += ACT_ADVANCE;
s = splvm();
TAILQ_REMOVE(&vm_page_queue_active, p, pageq);
TAILQ_INSERT_TAIL(&vm_page_queue_active, p, pageq);
splx(s);
}
} else if (p->queue == PQ_INACTIVE) {
vm_page_protect(p, VM_PROT_NONE);
}
p = next;
}
object = object->backing_object;
}
return;
}
/*
* deactivate some number of pages in a map, try to do it fairly, but
* that is really hard to do.
*/
static void
vm_pageout_map_deactivate_pages(map, desired)
vm_map_t map;
vm_pindex_t desired;
{
vm_map_entry_t tmpe;
vm_object_t obj, bigobj;
vm_map_reference(map);
if (lockmgr(&map->lock, LK_EXCLUSIVE | LK_NOWAIT, (void *)0, curproc)) {
vm_map_deallocate(map);
return;
}
bigobj = NULL;
/*
* first, search out the biggest object, and try to free pages from
* that.
*/
tmpe = map->header.next;
while (tmpe != &map->header) {
if ((tmpe->eflags & (MAP_ENTRY_IS_A_MAP|MAP_ENTRY_IS_SUB_MAP)) == 0) {
obj = tmpe->object.vm_object;
if ((obj != NULL) && (obj->shadow_count <= 1) &&
((bigobj == NULL) ||
(bigobj->resident_page_count < obj->resident_page_count))) {
bigobj = obj;
}
}
tmpe = tmpe->next;
}
if (bigobj)
vm_pageout_object_deactivate_pages(map, bigobj, desired, 0);
/*
* Next, hunt around for other pages to deactivate. We actually
* do this search sort of wrong -- .text first is not the best idea.
*/
tmpe = map->header.next;
while (tmpe != &map->header) {
if (vm_map_pmap(map)->pm_stats.resident_count <= desired)
break;
if ((tmpe->eflags & (MAP_ENTRY_IS_A_MAP|MAP_ENTRY_IS_SUB_MAP)) == 0) {
obj = tmpe->object.vm_object;
if (obj)
vm_pageout_object_deactivate_pages(map, obj, desired, 0);
}
tmpe = tmpe->next;
};
/*
* Remove all mappings if a process is swapped out, this will free page
* table pages.
*/
if (desired == 0)
pmap_remove(vm_map_pmap(map),
VM_MIN_ADDRESS, VM_MAXUSER_ADDRESS);
vm_map_unlock(map);
vm_map_deallocate(map);
return;
}
#endif
/*
* vm_pageout_scan does the dirty work for the pageout daemon.
*/
static int
vm_pageout_scan()
{
vm_page_t m, next;
int page_shortage, addl_page_shortage, maxscan, maxlaunder, pcount;
int pages_freed;
struct proc *p, *bigproc;
vm_offset_t size, bigsize;
vm_object_t object;
int force_wakeup = 0;
int actcount;
int vnodes_skipped = 0;
int s;
/*
* Start scanning the inactive queue for pages we can free. We keep
* scanning until we have enough free pages or we have scanned through
* the entire queue. If we encounter dirty pages, we start cleaning
* them.
*/
pages_freed = 0;
addl_page_shortage = 0;
maxlaunder = (cnt.v_inactive_target > MAXLAUNDER) ?
MAXLAUNDER : cnt.v_inactive_target;
rescan0:
maxscan = cnt.v_inactive_count;
for( m = TAILQ_FIRST(&vm_page_queue_inactive);
(m != NULL) && (maxscan-- > 0) &&
((cnt.v_cache_count + cnt.v_free_count) <
(cnt.v_cache_min + cnt.v_free_target));
m = next) {
cnt.v_pdpages++;
if (m->queue != PQ_INACTIVE) {
goto rescan0;
}
next = TAILQ_NEXT(m, pageq);
if (m->hold_count) {
s = splvm();
TAILQ_REMOVE(&vm_page_queue_inactive, m, pageq);
TAILQ_INSERT_TAIL(&vm_page_queue_inactive, m, pageq);
splx(s);
addl_page_shortage++;
continue;
}
/*
* Dont mess with busy pages, keep in the front of the
* queue, most likely are being paged out.
*/
if (m->busy || (m->flags & PG_BUSY)) {
addl_page_shortage++;
continue;
}
/*
* If the object is not being used, we ignore previous references.
*/
if (m->object->ref_count == 0) {
m->flags &= ~PG_REFERENCED;
pmap_clear_reference(VM_PAGE_TO_PHYS(m));
/*
* Otherwise, if the page has been referenced while in the inactive
* queue, we bump the "activation count" upwards, making it less
* likely that the page will be added back to the inactive queue
* prematurely again. Here we check the page tables (or emulated
* bits, if any), given the upper level VM system not knowing anything
* about existing references.
*/
} else if (((m->flags & PG_REFERENCED) == 0) &&
(actcount = pmap_ts_referenced(VM_PAGE_TO_PHYS(m)))) {
vm_page_activate(m);
m->act_count += (actcount + ACT_ADVANCE);
continue;
}
/*
* If the upper level VM system knows about any page references,
* we activate the page. We also set the "activation count" higher
* than normal so that we will less likely place pages back onto the
* inactive queue again.
*/
if ((m->flags & PG_REFERENCED) != 0) {
m->flags &= ~PG_REFERENCED;
#if 0
pmap_clear_reference(VM_PAGE_TO_PHYS(m));
#else
actcount = pmap_ts_referenced(VM_PAGE_TO_PHYS(m));
#endif
vm_page_activate(m);
m->act_count += (actcount + ACT_ADVANCE + 1);
continue;
}
/*
* If the upper level VM system doesn't know anything about the
* page being dirty, we have to check for it again. As far as the
* VM code knows, any partially dirty pages are fully dirty.
*/
if (m->dirty == 0) {
vm_page_test_dirty(m);
} else if (m->dirty != 0) {
m->dirty = VM_PAGE_BITS_ALL;
}
/*
* Invalid pages can be easily freed
*/
if (m->valid == 0) {
vm_page_protect(m, VM_PROT_NONE);
vm_page_free(m);
cnt.v_dfree++;
++pages_freed;
/*
* Clean pages can be placed onto the cache queue.
*/
} else if (m->dirty == 0) {
vm_page_cache(m);
++pages_freed;
/*
* Dirty pages need to be paged out. Note that we clean
* only a limited number of pages per pagedaemon pass.
*/
} else if (maxlaunder > 0) {
int written;
struct vnode *vp = NULL;
object = m->object;
/*
* We don't bother paging objects that are "dead". Those
* objects are in a "rundown" state.
*/
if (object->flags & OBJ_DEAD) {
s = splvm();
TAILQ_REMOVE(&vm_page_queue_inactive, m, pageq);
TAILQ_INSERT_TAIL(&vm_page_queue_inactive, m, pageq);
splx(s);
continue;
}
if (object->type == OBJT_VNODE) {
vp = object->handle;
if (VOP_ISLOCKED(vp) ||
vget(vp, LK_EXCLUSIVE, curproc)) {
if ((m->queue == PQ_INACTIVE) &&
(m->hold_count == 0) &&
(m->busy == 0) &&
(m->flags & PG_BUSY) == 0) {
s = splvm();
TAILQ_REMOVE(&vm_page_queue_inactive, m, pageq);
TAILQ_INSERT_TAIL(&vm_page_queue_inactive, m, pageq);
splx(s);
}
if (object->flags & OBJ_MIGHTBEDIRTY)
++vnodes_skipped;
continue;
}
/*
* The page might have been moved to another queue
* during potential blocking in vget() above.
*/
if (m->queue != PQ_INACTIVE) {
if (object->flags & OBJ_MIGHTBEDIRTY)
++vnodes_skipped;
vput(vp);
continue;
}
/*
* The page may have been busied during the blocking in
* vput(); We don't move the page back onto the end of
* the queue so that statistics are more correct if we don't.
*/
if (m->busy || (m->flags & PG_BUSY)) {
vput(vp);
continue;
}
/*
* If the page has become held, then skip it
*/
if (m->hold_count) {
s = splvm();
TAILQ_REMOVE(&vm_page_queue_inactive, m, pageq);
TAILQ_INSERT_TAIL(&vm_page_queue_inactive, m, pageq);
splx(s);
if (object->flags & OBJ_MIGHTBEDIRTY)
++vnodes_skipped;
vput(vp);
continue;
}
}
/*
* If a page is dirty, then it is either being washed
* (but not yet cleaned) or it is still in the
* laundry. If it is still in the laundry, then we
* start the cleaning operation.
*/
written = vm_pageout_clean(m, 0);
if (vp)
vput(vp);
maxlaunder -= written;
}
}
/*
* Compute the page shortage. If we are still very low on memory be
* sure that we will move a minimal amount of pages from active to
* inactive.
*/
page_shortage = (cnt.v_inactive_target + cnt.v_cache_min) -
(cnt.v_free_count + cnt.v_inactive_count + cnt.v_cache_count);
if (page_shortage <= 0) {
if (pages_freed == 0) {
page_shortage = cnt.v_free_min - cnt.v_free_count;
} else {
page_shortage = 1;
}
}
/*
* If the "inactive" loop finds that there is a shortage over and
* above the page statistics variables, then we need to accomodate
* that. This avoids potential deadlocks due to pages being temporarily
* busy for I/O or other types of temporary wiring.
*/
if (addl_page_shortage) {
if (page_shortage < 0)
page_shortage = 0;
page_shortage += addl_page_shortage;
}
pcount = cnt.v_active_count;
m = TAILQ_FIRST(&vm_page_queue_active);
while ((m != NULL) && (pcount-- > 0) && (page_shortage > 0)) {
/*
* This is a consistancy check, and should likely be a panic
* or warning.
*/
if (m->queue != PQ_ACTIVE) {
break;
}
next = TAILQ_NEXT(m, pageq);
/*
* Don't deactivate pages that are busy.
*/
if ((m->busy != 0) ||
(m->flags & PG_BUSY) ||
(m->hold_count != 0)) {
s = splvm();
TAILQ_REMOVE(&vm_page_queue_active, m, pageq);
TAILQ_INSERT_TAIL(&vm_page_queue_active, m, pageq);
splx(s);
m = next;
continue;
}
/*
* The count for pagedaemon pages is done after checking the
* page for eligbility...
*/
cnt.v_pdpages++;
/*
* Check to see "how much" the page has been used.
*/
actcount = 0;
if (m->object->ref_count != 0) {
if (m->flags & PG_REFERENCED) {
actcount += 1;
}
actcount += pmap_ts_referenced(VM_PAGE_TO_PHYS(m));
if (actcount) {
m->act_count += ACT_ADVANCE + actcount;
if (m->act_count > ACT_MAX)
m->act_count = ACT_MAX;
}
}
/*
* Since we have "tested" this bit, we need to clear it now.
*/
m->flags &= ~PG_REFERENCED;
/*
* Only if an object is currently being used, do we use the
* page activation count stats.
*/
if (actcount && (m->object->ref_count != 0)) {
s = splvm();
TAILQ_REMOVE(&vm_page_queue_active, m, pageq);
TAILQ_INSERT_TAIL(&vm_page_queue_active, m, pageq);
splx(s);
} else {
m->act_count -= min(m->act_count, ACT_DECLINE);
if (vm_pageout_algorithm_lru ||
(m->object->ref_count == 0) || (m->act_count == 0)) {
--page_shortage;
if (m->object->ref_count == 0) {
vm_page_protect(m, VM_PROT_NONE);
if (m->dirty == 0)
vm_page_cache(m);
else
vm_page_deactivate(m);
} else {
vm_page_deactivate(m);
}
} else {
s = splvm();
TAILQ_REMOVE(&vm_page_queue_active, m, pageq);
TAILQ_INSERT_TAIL(&vm_page_queue_active, m, pageq);
splx(s);
}
}
m = next;
}
s = splvm();
/*
* We try to maintain some *really* free pages, this allows interrupt
* code to be guaranteed space.
*/
while (cnt.v_free_count < cnt.v_free_reserved) {
static int cache_rover = 0;
m = vm_page_list_find(PQ_CACHE, cache_rover);
if (!m)
break;
cache_rover = (cache_rover + PQ_PRIME2) & PQ_L2_MASK;
vm_page_free(m);
cnt.v_dfree++;
}
splx(s);
/*
* If we didn't get enough free pages, and we have skipped a vnode
* in a writeable object, wakeup the sync daemon. And kick swapout
* if we did not get enough free pages.
*/
if ((cnt.v_cache_count + cnt.v_free_count) <
(cnt.v_free_target + cnt.v_cache_min) ) {
if (vnodes_skipped &&
(cnt.v_cache_count + cnt.v_free_count) < cnt.v_free_min) {
if (!vfs_update_wakeup) {
vfs_update_wakeup = 1;
wakeup(&vfs_update_wakeup);
}
}
#if !defined(NO_SWAPPING)
if (vm_swapping_enabled &&
(cnt.v_free_count + cnt.v_cache_count < cnt.v_free_target)) {
vm_req_vmdaemon();
vm_pageout_req_swapout = 1;
}
#endif
}
/*
* make sure that we have swap space -- if we are low on memory and
* swap -- then kill the biggest process.
*/
if ((vm_swap_size == 0 || swap_pager_full) &&
((cnt.v_free_count + cnt.v_cache_count) < cnt.v_free_min)) {
bigproc = NULL;
bigsize = 0;
for (p = allproc.lh_first; p != 0; p = p->p_list.le_next) {
/*
* if this is a system process, skip it
*/
if ((p->p_flag & P_SYSTEM) || (p->p_pid == 1) ||
((p->p_pid < 48) && (vm_swap_size != 0))) {
continue;
}
/*
* if the process is in a non-running type state,
* don't touch it.
*/
if (p->p_stat != SRUN && p->p_stat != SSLEEP) {
continue;
}
/*
* get the process size
*/
size = p->p_vmspace->vm_pmap.pm_stats.resident_count;
/*
* if the this process is bigger than the biggest one
* remember it.
*/
if (size > bigsize) {
bigproc = p;
bigsize = size;
}
}
if (bigproc != NULL) {
killproc(bigproc, "out of swap space");
bigproc->p_estcpu = 0;
bigproc->p_nice = PRIO_MIN;
resetpriority(bigproc);
wakeup(&cnt.v_free_count);
}
}
return force_wakeup;
}
/*
* This routine tries to maintain the pseudo LRU active queue,
* so that during long periods of time where there is no paging,
* that some statistic accumlation still occurs. This code
* helps the situation where paging just starts to occur.
*/
static void
vm_pageout_page_stats()
{
int s;
vm_page_t m,next;
int pcount,tpcount; /* Number of pages to check */
static int fullintervalcount = 0;
pcount = cnt.v_active_count;
fullintervalcount += vm_pageout_stats_interval;
if (fullintervalcount < vm_pageout_full_stats_interval) {
tpcount = (vm_pageout_stats_max * cnt.v_active_count) / cnt.v_page_count;
if (pcount > tpcount)
pcount = tpcount;
}
m = TAILQ_FIRST(&vm_page_queue_active);
while ((m != NULL) && (pcount-- > 0)) {
int actcount;
if (m->queue != PQ_ACTIVE) {
break;
}
next = TAILQ_NEXT(m, pageq);
/*
* Don't deactivate pages that are busy.
*/
if ((m->busy != 0) ||
(m->flags & PG_BUSY) ||
(m->hold_count != 0)) {
s = splvm();
TAILQ_REMOVE(&vm_page_queue_active, m, pageq);
TAILQ_INSERT_TAIL(&vm_page_queue_active, m, pageq);
splx(s);
m = next;
continue;
}
actcount = 0;
if (m->flags & PG_REFERENCED) {
m->flags &= ~PG_REFERENCED;
actcount += 1;
}
actcount += pmap_ts_referenced(VM_PAGE_TO_PHYS(m));
if (actcount) {
m->act_count += ACT_ADVANCE + actcount;
if (m->act_count > ACT_MAX)
m->act_count = ACT_MAX;
s = splvm();
TAILQ_REMOVE(&vm_page_queue_active, m, pageq);
TAILQ_INSERT_TAIL(&vm_page_queue_active, m, pageq);
splx(s);
} else {
if (m->act_count == 0) {
/*
* We turn off page access, so that we have more accurate
* RSS stats. We don't do this in the normal page deactivation
* when the system is loaded VM wise, because the cost of
* the large number of page protect operations would be higher
* than the value of doing the operation.
*/
vm_page_protect(m, VM_PROT_NONE);
vm_page_deactivate(m);
} else {
m->act_count -= min(m->act_count, ACT_DECLINE);
s = splvm();
TAILQ_REMOVE(&vm_page_queue_active, m, pageq);
TAILQ_INSERT_TAIL(&vm_page_queue_active, m, pageq);
splx(s);
}
}
m = next;
}
}
static int
vm_pageout_free_page_calc(count)
vm_size_t count;
{
if (count < cnt.v_page_count)
return 0;
/*
* free_reserved needs to include enough for the largest swap pager
* structures plus enough for any pv_entry structs when paging.
*/
if (cnt.v_page_count > 1024)
cnt.v_free_min = 4 + (cnt.v_page_count - 1024) / 200;
else
cnt.v_free_min = 4;
cnt.v_pageout_free_min = (2*MAXBSIZE)/PAGE_SIZE +
cnt.v_interrupt_free_min;
cnt.v_free_reserved = vm_pageout_page_count +
cnt.v_pageout_free_min + (count / 768) + PQ_L2_SIZE;
cnt.v_free_min += cnt.v_free_reserved;
return 1;
}
/*
* vm_pageout is the high level pageout daemon.
*/
static void
vm_pageout()
{
/*
* Initialize some paging parameters.
*/
cnt.v_interrupt_free_min = 2;
if (cnt.v_page_count < 2000)
vm_pageout_page_count = 8;
vm_pageout_free_page_calc(cnt.v_page_count);
/*
* free_reserved needs to include enough for the largest swap pager
* structures plus enough for any pv_entry structs when paging.
*/
cnt.v_free_target = 3 * cnt.v_free_min + cnt.v_free_reserved;
if (cnt.v_free_count > 1024) {
cnt.v_cache_max = (cnt.v_free_count - 1024) / 2;
cnt.v_cache_min = (cnt.v_free_count - 1024) / 8;
cnt.v_inactive_target = 2*cnt.v_cache_min + 192;
} else {
cnt.v_cache_min = 0;
cnt.v_cache_max = 0;
cnt.v_inactive_target = cnt.v_free_count / 4;
}
/* XXX does not really belong here */
if (vm_page_max_wired == 0)
vm_page_max_wired = cnt.v_free_count / 3;
if (vm_pageout_stats_max == 0)
vm_pageout_stats_max = cnt.v_free_target;
/*
* Set interval in seconds for stats scan.
*/
if (vm_pageout_stats_interval == 0)
vm_pageout_stats_interval = 4;
if (vm_pageout_full_stats_interval == 0)
vm_pageout_full_stats_interval = vm_pageout_stats_interval * 4;
/*
* Set maximum free per pass
*/
if (vm_pageout_stats_free_max == 0)
vm_pageout_stats_free_max = 25;
swap_pager_swap_init();
/*
* The pageout daemon is never done, so loop forever.
*/
while (TRUE) {
int inactive_target;
int error;
int s = splvm();
if (!vm_pages_needed ||
((cnt.v_free_count + cnt.v_cache_count) > cnt.v_free_min)) {
vm_pages_needed = 0;
error = tsleep(&vm_pages_needed,
PVM, "psleep", vm_pageout_stats_interval * hz);
if (error && !vm_pages_needed) {
splx(s);
vm_pageout_page_stats();
continue;
}
} else if (vm_pages_needed) {
tsleep(&vm_pages_needed, PVM, "psleep", hz/10);
}
inactive_target =
(cnt.v_page_count - cnt.v_wire_count) / 4;
if (inactive_target < 2*cnt.v_free_min)
inactive_target = 2*cnt.v_free_min;
cnt.v_inactive_target = inactive_target;
if (vm_pages_needed)
cnt.v_pdwakeups++;
vm_pages_needed = 0;
splx(s);
vm_pager_sync();
vm_pageout_scan();
vm_pager_sync();
wakeup(&cnt.v_free_count);
}
}
void
pagedaemon_wakeup()
{
if (!vm_pages_needed && curproc != pageproc) {
vm_pages_needed++;
wakeup(&vm_pages_needed);
}
}
#if !defined(NO_SWAPPING)
static void
vm_req_vmdaemon()
{
static int lastrun = 0;
if ((ticks > (lastrun + hz)) || (ticks < lastrun)) {
wakeup(&vm_daemon_needed);
lastrun = ticks;
}
}
static void
vm_daemon()
{
vm_object_t object;
struct proc *p;
while (TRUE) {
tsleep(&vm_daemon_needed, PUSER, "psleep", 0);
if (vm_pageout_req_swapout) {
swapout_procs();
vm_pageout_req_swapout = 0;
}
/*
* scan the processes for exceeding their rlimits or if
* process is swapped out -- deactivate pages
*/
for (p = allproc.lh_first; p != 0; p = p->p_list.le_next) {
quad_t limit;
vm_offset_t size;
/*
* if this is a system process or if we have already
* looked at this process, skip it.
*/
if (p->p_flag & (P_SYSTEM | P_WEXIT)) {
continue;
}
/*
* if the process is in a non-running type state,
* don't touch it.
*/
if (p->p_stat != SRUN && p->p_stat != SSLEEP) {
continue;
}
/*
* get a limit
*/
limit = qmin(p->p_rlimit[RLIMIT_RSS].rlim_cur,
p->p_rlimit[RLIMIT_RSS].rlim_max);
/*
* let processes that are swapped out really be
* swapped out set the limit to nothing (will force a
* swap-out.)
*/
if ((p->p_flag & P_INMEM) == 0)
limit = 0; /* XXX */
size = p->p_vmspace->vm_pmap.pm_stats.resident_count * PAGE_SIZE;
if (limit >= 0 && size >= limit) {
vm_pageout_map_deactivate_pages(&p->p_vmspace->vm_map,
(vm_pindex_t)(limit >> PAGE_SHIFT) );
}
}
/*
* we remove cached objects that have no RSS...
*/
restart:
object = TAILQ_FIRST(&vm_object_cached_list);
while (object) {
/*
* if there are no resident pages -- get rid of the object
*/
if (object->resident_page_count == 0) {
vm_object_reference(object);
pager_cache(object, FALSE);
goto restart;
}
object = TAILQ_NEXT(object, cached_list);
}
}
}
#endif
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