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freebsd-skq/sys/vm/vm_pageout.c
kib a9d505a22a Split the vm_page flags PG_WRITEABLE and PG_REFERENCED into atomic 
flags field. Updates to the atomic flags are performed using the atomic
ops on the containing word, do not require any vm lock to be held, and
are non-blocking. The vm_page_aflag_set(9) and vm_page_aflag_clear(9)
functions are provided to modify afalgs.

Document the changes to flags field to only require the page lock.

Introduce vm_page_reference(9) function to provide a stable KPI and
KBI for filesystems like tmpfs and zfs which need to mark a page as
referenced.

Reviewed by:    alc, attilio
Tested by:      marius, flo (sparc64); andreast (powerpc, powerpc64)
Approved by:	re (bz)
2011-09-06 10:30:11 +00:00

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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.
* Copyright (c) 2005 Yahoo! Technologies Norway AS
* 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.
*/
/*
* The proverbial page-out daemon.
*/
#include <sys/cdefs.h>
__FBSDID("$FreeBSD$");
#include "opt_vm.h"
#include <sys/param.h>
#include <sys/systm.h>
#include <sys/kernel.h>
#include <sys/eventhandler.h>
#include <sys/lock.h>
#include <sys/mutex.h>
#include <sys/proc.h>
#include <sys/kthread.h>
#include <sys/ktr.h>
#include <sys/mount.h>
#include <sys/racct.h>
#include <sys/resourcevar.h>
#include <sys/sched.h>
#include <sys/signalvar.h>
#include <sys/vnode.h>
#include <sys/vmmeter.h>
#include <sys/sx.h>
#include <sys/sysctl.h>
#include <vm/vm.h>
#include <vm/vm_param.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>
#include <vm/uma.h>
/*
* System initialization
*/
/* the kernel process "vm_pageout"*/
static void vm_pageout(void);
static int vm_pageout_clean(vm_page_t);
static void vm_pageout_scan(int pass);
struct proc *pageproc;
static struct kproc_desc page_kp = {
"pagedaemon",
vm_pageout,
&pageproc
};
SYSINIT(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(void);
static struct proc *vmproc;
static struct kproc_desc vm_kp = {
"vmdaemon",
vm_daemon,
&vmproc
};
SYSINIT(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_deficit; /* Estimated number of pages deficit */
int vm_pageout_pages_needed; /* flag saying that the pageout daemon needs pages */
#if !defined(NO_SWAPPING)
static int vm_pageout_req_swapout; /* XXX */
static int vm_daemon_needed;
static struct mtx vm_daemon_mtx;
/* Allow for use by vm_pageout before vm_daemon is initialized. */
MTX_SYSINIT(vm_daemon, &vm_daemon_mtx, "vm daemon", MTX_DEF);
#endif
static int vm_max_launder = 32;
static int vm_pageout_stats_max=0, vm_pageout_stats_interval = 0;
static int vm_pageout_full_stats_interval = 0;
static int vm_pageout_algorithm=0;
static int defer_swap_pageouts=0;
static int disable_swap_pageouts=0;
#if defined(NO_SWAPPING)
static int vm_swap_enabled=0;
static int vm_swap_idle_enabled=0;
#else
static int vm_swap_enabled=1;
static int vm_swap_idle_enabled=0;
#endif
SYSCTL_INT(_vm, VM_PAGEOUT_ALGORITHM, pageout_algorithm,
CTLFLAG_RW, &vm_pageout_algorithm, 0, "LRU page mgmt");
SYSCTL_INT(_vm, OID_AUTO, max_launder,
CTLFLAG_RW, &vm_max_launder, 0, "Limit dirty flushes in pageout");
SYSCTL_INT(_vm, OID_AUTO, pageout_stats_max,
CTLFLAG_RW, &vm_pageout_stats_max, 0, "Max pageout stats scan length");
SYSCTL_INT(_vm, OID_AUTO, pageout_full_stats_interval,
CTLFLAG_RW, &vm_pageout_full_stats_interval, 0, "Interval for full stats scan");
SYSCTL_INT(_vm, OID_AUTO, pageout_stats_interval,
CTLFLAG_RW, &vm_pageout_stats_interval, 0, "Interval for partial stats scan");
#if defined(NO_SWAPPING)
SYSCTL_INT(_vm, VM_SWAPPING_ENABLED, swap_enabled,
CTLFLAG_RD, &vm_swap_enabled, 0, "Enable entire process swapout");
SYSCTL_INT(_vm, OID_AUTO, swap_idle_enabled,
CTLFLAG_RD, &vm_swap_idle_enabled, 0, "Allow swapout on idle criteria");
#else
SYSCTL_INT(_vm, VM_SWAPPING_ENABLED, swap_enabled,
CTLFLAG_RW, &vm_swap_enabled, 0, "Enable entire process swapout");
SYSCTL_INT(_vm, OID_AUTO, swap_idle_enabled,
CTLFLAG_RW, &vm_swap_idle_enabled, 0, "Allow swapout on idle criteria");
#endif
SYSCTL_INT(_vm, OID_AUTO, defer_swapspace_pageouts,
CTLFLAG_RW, &defer_swap_pageouts, 0, "Give preference to dirty pages in mem");
SYSCTL_INT(_vm, OID_AUTO, disable_swapspace_pageouts,
CTLFLAG_RW, &disable_swap_pageouts, 0, "Disallow swapout of dirty pages");
static int pageout_lock_miss;
SYSCTL_INT(_vm, OID_AUTO, pageout_lock_miss,
CTLFLAG_RD, &pageout_lock_miss, 0, "vget() lock misses during pageout");
#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 */
SYSCTL_INT(_vm, OID_AUTO, max_wired,
CTLFLAG_RW, &vm_page_max_wired, 0, "System-wide limit to wired page count");
#if !defined(NO_SWAPPING)
static void vm_pageout_map_deactivate_pages(vm_map_t, long);
static void vm_pageout_object_deactivate_pages(pmap_t, vm_object_t, long);
static void vm_req_vmdaemon(int req);
#endif
static void vm_pageout_page_stats(void);
/*
* Initialize a dummy page for marking the caller's place in the specified
* paging queue. In principle, this function only needs to set the flag
* PG_MARKER. Nonetheless, it sets the flag VPO_BUSY and initializes the hold
* count to one as safety precautions.
*/
static void
vm_pageout_init_marker(vm_page_t marker, u_short queue)
{
bzero(marker, sizeof(*marker));
marker->flags = PG_MARKER;
marker->oflags = VPO_BUSY;
marker->queue = queue;
marker->hold_count = 1;
}
/*
* vm_pageout_fallback_object_lock:
*
* Lock vm object currently associated with `m'. VM_OBJECT_TRYLOCK is
* known to have failed and page queue must be either PQ_ACTIVE or
* PQ_INACTIVE. To avoid lock order violation, unlock the page queues
* while locking the vm object. Use marker page to detect page queue
* changes and maintain notion of next page on page queue. Return
* TRUE if no changes were detected, FALSE otherwise. vm object is
* locked on return.
*
* This function depends on both the lock portion of struct vm_object
* and normal struct vm_page being type stable.
*/
boolean_t
vm_pageout_fallback_object_lock(vm_page_t m, vm_page_t *next)
{
struct vm_page marker;
boolean_t unchanged;
u_short queue;
vm_object_t object;
queue = m->queue;
vm_pageout_init_marker(&marker, queue);
object = m->object;
TAILQ_INSERT_AFTER(&vm_page_queues[queue].pl,
m, &marker, pageq);
vm_page_unlock_queues();
vm_page_unlock(m);
VM_OBJECT_LOCK(object);
vm_page_lock(m);
vm_page_lock_queues();
/* Page queue might have changed. */
*next = TAILQ_NEXT(&marker, pageq);
unchanged = (m->queue == queue &&
m->object == object &&
&marker == TAILQ_NEXT(m, pageq));
TAILQ_REMOVE(&vm_page_queues[queue].pl,
&marker, pageq);
return (unchanged);
}
/*
* Lock the page while holding the page queue lock. Use marker page
* to detect page queue changes and maintain notion of next page on
* page queue. Return TRUE if no changes were detected, FALSE
* otherwise. The page is locked on return. The page queue lock might
* be dropped and reacquired.
*
* This function depends on normal struct vm_page being type stable.
*/
boolean_t
vm_pageout_page_lock(vm_page_t m, vm_page_t *next)
{
struct vm_page marker;
boolean_t unchanged;
u_short queue;
vm_page_lock_assert(m, MA_NOTOWNED);
mtx_assert(&vm_page_queue_mtx, MA_OWNED);
if (vm_page_trylock(m))
return (TRUE);
queue = m->queue;
vm_pageout_init_marker(&marker, queue);
TAILQ_INSERT_AFTER(&vm_page_queues[queue].pl, m, &marker, pageq);
vm_page_unlock_queues();
vm_page_lock(m);
vm_page_lock_queues();
/* Page queue might have changed. */
*next = TAILQ_NEXT(&marker, pageq);
unchanged = (m->queue == queue && &marker == TAILQ_NEXT(m, pageq));
TAILQ_REMOVE(&vm_page_queues[queue].pl, &marker, pageq);
return (unchanged);
}
/*
* 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. Note the careful timing, however, the busy bit isn't set till
* late and we cannot do anything that will mess with the page.
*/
static int
vm_pageout_clean(vm_page_t m)
{
vm_object_t object;
vm_page_t mc[2*vm_pageout_page_count], pb, ps;
int pageout_count;
int ib, is, page_base;
vm_pindex_t pindex = m->pindex;
vm_page_lock_assert(m, MA_OWNED);
object = m->object;
VM_OBJECT_LOCK_ASSERT(object, MA_OWNED);
/*
* It doesn't cost us anything to pageout OBJT_DEFAULT or OBJT_SWAP
* with the new swapper, but we could have serious problems paging
* out other object types if there is insufficient memory.
*
* Unfortunately, checking free memory here is far too late, so the
* check has been moved up a procedural level.
*/
/*
* Can't clean the page if it's busy or held.
*/
KASSERT(m->busy == 0 && (m->oflags & VPO_BUSY) == 0,
("vm_pageout_clean: page %p is busy", m));
KASSERT(m->hold_count == 0, ("vm_pageout_clean: page %p is held", m));
vm_page_unlock(m);
mc[vm_pageout_page_count] = pb = ps = m;
pageout_count = 1;
page_base = vm_pageout_page_count;
ib = 1;
is = 1;
/*
* 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.
*
* During heavy mmap/modification loads the pageout
* daemon can really fragment the underlying file
* due to flushing pages out of order and not trying
* align the clusters (which leave sporatic out-of-order
* holes). To solve this problem we do the reverse scan
* first and attempt to align our cluster, then do a
* forward scan if room remains.
*/
more:
while (ib && pageout_count < vm_pageout_page_count) {
vm_page_t p;
if (ib > pindex) {
ib = 0;
break;
}
if ((p = vm_page_prev(pb)) == NULL ||
(p->oflags & VPO_BUSY) != 0 || p->busy != 0) {
ib = 0;
break;
}
vm_page_lock(p);
vm_page_test_dirty(p);
if (p->dirty == 0 ||
p->queue != PQ_INACTIVE ||
p->hold_count != 0) { /* may be undergoing I/O */
vm_page_unlock(p);
ib = 0;
break;
}
vm_page_unlock(p);
mc[--page_base] = pb = p;
++pageout_count;
++ib;
/*
* alignment boundry, stop here and switch directions. Do
* not clear ib.
*/
if ((pindex - (ib - 1)) % vm_pageout_page_count == 0)
break;
}
while (pageout_count < vm_pageout_page_count &&
pindex + is < object->size) {
vm_page_t p;
if ((p = vm_page_next(ps)) == NULL ||
(p->oflags & VPO_BUSY) != 0 || p->busy != 0)
break;
vm_page_lock(p);
vm_page_test_dirty(p);
if (p->dirty == 0 ||
p->queue != PQ_INACTIVE ||
p->hold_count != 0) { /* may be undergoing I/O */
vm_page_unlock(p);
break;
}
vm_page_unlock(p);
mc[page_base + pageout_count] = ps = p;
++pageout_count;
++is;
}
/*
* If we exhausted our forward scan, continue with the reverse scan
* when possible, even past a page boundry. This catches boundry
* conditions.
*/
if (ib && pageout_count < vm_pageout_page_count)
goto more;
/*
* we allow reads during pageouts...
*/
return (vm_pageout_flush(&mc[page_base], pageout_count, 0, 0, NULL));
}
/*
* vm_pageout_flush() - launder the given pages
*
* The given pages are laundered. Note that we setup for the start of
* I/O ( i.e. busy the page ), mark it read-only, and bump the object
* reference count all in here rather then in the parent. If we want
* the parent to do more sophisticated things we may have to change
* the ordering.
*
* Returned runlen is the count of pages between mreq and first
* page after mreq with status VM_PAGER_AGAIN.
*/
int
vm_pageout_flush(vm_page_t *mc, int count, int flags, int mreq, int *prunlen)
{
vm_object_t object = mc[0]->object;
int pageout_status[count];
int numpagedout = 0;
int i, runlen;
VM_OBJECT_LOCK_ASSERT(object, MA_OWNED);
mtx_assert(&vm_page_queue_mtx, MA_NOTOWNED);
/*
* Initiate I/O. Bump the vm_page_t->busy counter and
* mark the pages read-only.
*
* We do not have to fixup the clean/dirty bits here... we can
* allow the pager to do it after the I/O completes.
*
* NOTE! mc[i]->dirty may be partial or fragmented due to an
* edge case with file fragments.
*/
for (i = 0; i < count; i++) {
KASSERT(mc[i]->valid == VM_PAGE_BITS_ALL,
("vm_pageout_flush: partially invalid page %p index %d/%d",
mc[i], i, count));
vm_page_io_start(mc[i]);
pmap_remove_write(mc[i]);
}
vm_object_pip_add(object, count);
vm_pager_put_pages(object, mc, count, flags, pageout_status);
runlen = count - mreq;
for (i = 0; i < count; i++) {
vm_page_t mt = mc[i];
KASSERT(pageout_status[i] == VM_PAGER_PEND ||
(mt->aflags & PGA_WRITEABLE) == 0,
("vm_pageout_flush: page %p is not write protected", mt));
switch (pageout_status[i]) {
case VM_PAGER_OK:
case VM_PAGER_PEND:
numpagedout++;
break;
case VM_PAGER_BAD:
/*
* Page outside of range of object. Right now we
* essentially lose the changes by pretending it
* worked.
*/
vm_page_undirty(mt);
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).
*/
vm_page_lock(mt);
vm_page_activate(mt);
vm_page_unlock(mt);
break;
case VM_PAGER_AGAIN:
if (i >= mreq && i - mreq < runlen)
runlen = i - mreq;
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);
vm_page_io_finish(mt);
if (vm_page_count_severe()) {
vm_page_lock(mt);
vm_page_try_to_cache(mt);
vm_page_unlock(mt);
}
}
}
if (prunlen != NULL)
*prunlen = runlen;
return (numpagedout);
}
#if !defined(NO_SWAPPING)
/*
* vm_pageout_object_deactivate_pages
*
* Deactivate enough pages to satisfy the inactive target
* requirements.
*
* The object and map must be locked.
*/
static void
vm_pageout_object_deactivate_pages(pmap_t pmap, vm_object_t first_object,
long desired)
{
vm_object_t backing_object, object;
vm_page_t p;
int actcount, remove_mode;
VM_OBJECT_LOCK_ASSERT(first_object, MA_OWNED);
if (first_object->type == OBJT_DEVICE ||
first_object->type == OBJT_SG)
return;
for (object = first_object;; object = backing_object) {
if (pmap_resident_count(pmap) <= desired)
goto unlock_return;
VM_OBJECT_LOCK_ASSERT(object, MA_OWNED);
if (object->type == OBJT_PHYS || object->paging_in_progress)
goto unlock_return;
remove_mode = 0;
if (object->shadow_count > 1)
remove_mode = 1;
/*
* Scan the object's entire memory queue.
*/
TAILQ_FOREACH(p, &object->memq, listq) {
if (pmap_resident_count(pmap) <= desired)
goto unlock_return;
if ((p->oflags & VPO_BUSY) != 0 || p->busy != 0)
continue;
PCPU_INC(cnt.v_pdpages);
vm_page_lock(p);
if (p->wire_count != 0 || p->hold_count != 0 ||
!pmap_page_exists_quick(pmap, p)) {
vm_page_unlock(p);
continue;
}
actcount = pmap_ts_referenced(p);
if ((p->aflags & PGA_REFERENCED) != 0) {
if (actcount == 0)
actcount = 1;
vm_page_aflag_clear(p, PGA_REFERENCED);
}
if (p->queue != PQ_ACTIVE && actcount != 0) {
vm_page_activate(p);
p->act_count += actcount;
} else if (p->queue == PQ_ACTIVE) {
if (actcount == 0) {
p->act_count -= min(p->act_count,
ACT_DECLINE);
if (!remove_mode &&
(vm_pageout_algorithm ||
p->act_count == 0)) {
pmap_remove_all(p);
vm_page_deactivate(p);
} else {
vm_page_lock_queues();
vm_page_requeue(p);
vm_page_unlock_queues();
}
} else {
vm_page_activate(p);
if (p->act_count < ACT_MAX -
ACT_ADVANCE)
p->act_count += ACT_ADVANCE;
vm_page_lock_queues();
vm_page_requeue(p);
vm_page_unlock_queues();
}
} else if (p->queue == PQ_INACTIVE)
pmap_remove_all(p);
vm_page_unlock(p);
}
if ((backing_object = object->backing_object) == NULL)
goto unlock_return;
VM_OBJECT_LOCK(backing_object);
if (object != first_object)
VM_OBJECT_UNLOCK(object);
}
unlock_return:
if (object != first_object)
VM_OBJECT_UNLOCK(object);
}
/*
* 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;
long desired;
{
vm_map_entry_t tmpe;
vm_object_t obj, bigobj;
int nothingwired;
if (!vm_map_trylock(map))
return;
bigobj = NULL;
nothingwired = TRUE;
/*
* 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_SUB_MAP) == 0) {
obj = tmpe->object.vm_object;
if (obj != NULL && VM_OBJECT_TRYLOCK(obj)) {
if (obj->shadow_count <= 1 &&
(bigobj == NULL ||
bigobj->resident_page_count < obj->resident_page_count)) {
if (bigobj != NULL)
VM_OBJECT_UNLOCK(bigobj);
bigobj = obj;
} else
VM_OBJECT_UNLOCK(obj);
}
}
if (tmpe->wired_count > 0)
nothingwired = FALSE;
tmpe = tmpe->next;
}
if (bigobj != NULL) {
vm_pageout_object_deactivate_pages(map->pmap, bigobj, desired);
VM_OBJECT_UNLOCK(bigobj);
}
/*
* 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 (pmap_resident_count(vm_map_pmap(map)) <= desired)
break;
if ((tmpe->eflags & MAP_ENTRY_IS_SUB_MAP) == 0) {
obj = tmpe->object.vm_object;
if (obj != NULL) {
VM_OBJECT_LOCK(obj);
vm_pageout_object_deactivate_pages(map->pmap, obj, desired);
VM_OBJECT_UNLOCK(obj);
}
}
tmpe = tmpe->next;
}
/*
* Remove all mappings if a process is swapped out, this will free page
* table pages.
*/
if (desired == 0 && nothingwired) {
tmpe = map->header.next;
while (tmpe != &map->header) {
pmap_remove(vm_map_pmap(map), tmpe->start, tmpe->end);
tmpe = tmpe->next;
}
}
vm_map_unlock(map);
}
#endif /* !defined(NO_SWAPPING) */
/*
* vm_pageout_scan does the dirty work for the pageout daemon.
*/
static void
vm_pageout_scan(int pass)
{
vm_page_t m, next;
struct vm_page marker;
int page_shortage, maxscan, pcount;
int addl_page_shortage, addl_page_shortage_init;
vm_object_t object;
int actcount;
int vnodes_skipped = 0;
int maxlaunder;
/*
* Decrease registered cache sizes.
*/
EVENTHANDLER_INVOKE(vm_lowmem, 0);
/*
* We do this explicitly after the caches have been drained above.
*/
uma_reclaim();
addl_page_shortage_init = atomic_readandclear_int(&vm_pageout_deficit);
/*
* Calculate the number of pages we want to either free or move
* to the cache.
*/
page_shortage = vm_paging_target() + addl_page_shortage_init;
vm_pageout_init_marker(&marker, PQ_INACTIVE);
/*
* Start scanning the inactive queue for pages we can move to the
* cache or free. The scan will stop when the target is reached or
* we have scanned the entire inactive queue. Note that m->act_count
* is not used to form decisions for the inactive queue, only for the
* active queue.
*
* maxlaunder limits the number of dirty pages we flush per scan.
* For most systems a smaller value (16 or 32) is more robust under
* extreme memory and disk pressure because any unnecessary writes
* to disk can result in extreme performance degredation. However,
* systems with excessive dirty pages (especially when MAP_NOSYNC is
* used) will die horribly with limited laundering. If the pageout
* daemon cannot clean enough pages in the first pass, we let it go
* all out in succeeding passes.
*/
if ((maxlaunder = vm_max_launder) <= 1)
maxlaunder = 1;
if (pass)
maxlaunder = 10000;
vm_page_lock_queues();
rescan0:
addl_page_shortage = addl_page_shortage_init;
maxscan = cnt.v_inactive_count;
for (m = TAILQ_FIRST(&vm_page_queues[PQ_INACTIVE].pl);
m != NULL && maxscan-- > 0 && page_shortage > 0;
m = next) {
cnt.v_pdpages++;
if (m->queue != PQ_INACTIVE)
goto rescan0;
next = TAILQ_NEXT(m, pageq);
/*
* skip marker pages
*/
if (m->flags & PG_MARKER)
continue;
/*
* Lock the page.
*/
if (!vm_pageout_page_lock(m, &next)) {
vm_page_unlock(m);
addl_page_shortage++;
continue;
}
/*
* A held page may be undergoing I/O, so skip it.
*/
if (m->hold_count) {
vm_page_unlock(m);
vm_page_requeue(m);
addl_page_shortage++;
continue;
}
/*
* Don't mess with busy pages, keep in the front of the
* queue, most likely are being paged out.
*/
object = m->object;
if (!VM_OBJECT_TRYLOCK(object) &&
(!vm_pageout_fallback_object_lock(m, &next) ||
m->hold_count != 0)) {
VM_OBJECT_UNLOCK(object);
vm_page_unlock(m);
addl_page_shortage++;
continue;
}
if (m->busy || (m->oflags & VPO_BUSY)) {
vm_page_unlock(m);
VM_OBJECT_UNLOCK(object);
addl_page_shortage++;
continue;
}
/*
* If the object is not being used, we ignore previous
* references.
*/
if (object->ref_count == 0) {
vm_page_aflag_clear(m, PGA_REFERENCED);
KASSERT(!pmap_page_is_mapped(m),
("vm_pageout_scan: page %p is mapped", 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->aflags & PGA_REFERENCED) == 0) &&
(actcount = pmap_ts_referenced(m))) {
vm_page_activate(m);
vm_page_unlock(m);
m->act_count += actcount + ACT_ADVANCE;
VM_OBJECT_UNLOCK(object);
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->aflags & PGA_REFERENCED) != 0) {
vm_page_aflag_clear(m, PGA_REFERENCED);
actcount = pmap_ts_referenced(m);
vm_page_activate(m);
vm_page_unlock(m);
m->act_count += actcount + ACT_ADVANCE + 1;
VM_OBJECT_UNLOCK(object);
continue;
}
/*
* If the upper level VM system does not believe that the page
* is fully dirty, but it is mapped for write access, then we
* consult the pmap to see if the page's dirty status should
* be updated.
*/
if (m->dirty != VM_PAGE_BITS_ALL &&
(m->aflags & PGA_WRITEABLE) != 0) {
/*
* Avoid a race condition: Unless write access is
* removed from the page, another processor could
* modify it before all access is removed by the call
* to vm_page_cache() below. If vm_page_cache() finds
* that the page has been modified when it removes all
* access, it panics because it cannot cache dirty
* pages. In principle, we could eliminate just write
* access here rather than all access. In the expected
* case, when there are no last instant modifications
* to the page, removing all access will be cheaper
* overall.
*/
if (pmap_is_modified(m))
vm_page_dirty(m);
else if (m->dirty == 0)
pmap_remove_all(m);
}
if (m->valid == 0) {
/*
* Invalid pages can be easily freed
*/
vm_page_free(m);
cnt.v_dfree++;
--page_shortage;
} else if (m->dirty == 0) {
/*
* Clean pages can be placed onto the cache queue.
* This effectively frees them.
*/
vm_page_cache(m);
--page_shortage;
} else if ((m->flags & PG_WINATCFLS) == 0 && pass == 0) {
/*
* Dirty pages need to be paged out, but flushing
* a page is extremely expensive verses freeing
* a clean page. Rather then artificially limiting
* the number of pages we can flush, we instead give
* dirty pages extra priority on the inactive queue
* by forcing them to be cycled through the queue
* twice before being flushed, after which the
* (now clean) page will cycle through once more
* before being freed. This significantly extends
* the thrash point for a heavily loaded machine.
*/
m->flags |= PG_WINATCFLS;
vm_page_requeue(m);
} else if (maxlaunder > 0) {
/*
* We always want to try to flush some dirty pages if
* we encounter them, to keep the system stable.
* Normally this number is small, but under extreme
* pressure where there are insufficient clean pages
* on the inactive queue, we may have to go all out.
*/
int swap_pageouts_ok, vfslocked = 0;
struct vnode *vp = NULL;
struct mount *mp = NULL;
if ((object->type != OBJT_SWAP) && (object->type != OBJT_DEFAULT)) {
swap_pageouts_ok = 1;
} else {
swap_pageouts_ok = !(defer_swap_pageouts || disable_swap_pageouts);
swap_pageouts_ok |= (!disable_swap_pageouts && defer_swap_pageouts &&
vm_page_count_min());
}
/*
* We don't bother paging objects that are "dead".
* Those objects are in a "rundown" state.
*/
if (!swap_pageouts_ok || (object->flags & OBJ_DEAD)) {
vm_page_unlock(m);
VM_OBJECT_UNLOCK(object);
vm_page_requeue(m);
continue;
}
/*
* Following operations may unlock
* vm_page_queue_mtx, invalidating the 'next'
* pointer. To prevent an inordinate number
* of restarts we use our marker to remember
* our place.
*
*/
TAILQ_INSERT_AFTER(&vm_page_queues[PQ_INACTIVE].pl,
m, &marker, pageq);
/*
* The object is already known NOT to be dead. It
* is possible for the vget() to block the whole
* pageout daemon, but the new low-memory handling
* code should prevent it.
*
* The previous code skipped locked vnodes and, worse,
* reordered pages in the queue. This results in
* completely non-deterministic operation and, on a
* busy system, can lead to extremely non-optimal
* pageouts. For example, it can cause clean pages
* to be freed and dirty pages to be moved to the end
* of the queue. Since dirty pages are also moved to
* the end of the queue once-cleaned, this gives
* way too large a weighting to defering the freeing
* of dirty pages.
*
* We can't wait forever for the vnode lock, we might
* deadlock due to a vn_read() getting stuck in
* vm_wait while holding this vnode. We skip the
* vnode if we can't get it in a reasonable amount
* of time.
*/
if (object->type == OBJT_VNODE) {
vm_page_unlock_queues();
vm_page_unlock(m);
vp = object->handle;
if (vp->v_type == VREG &&
vn_start_write(vp, &mp, V_NOWAIT) != 0) {
mp = NULL;
++pageout_lock_miss;
if (object->flags & OBJ_MIGHTBEDIRTY)
vnodes_skipped++;
vm_page_lock_queues();
goto unlock_and_continue;
}
KASSERT(mp != NULL,
("vp %p with NULL v_mount", vp));
vm_object_reference_locked(object);
VM_OBJECT_UNLOCK(object);
vfslocked = VFS_LOCK_GIANT(vp->v_mount);
if (vget(vp, LK_EXCLUSIVE | LK_TIMELOCK,
curthread)) {
VM_OBJECT_LOCK(object);
vm_page_lock_queues();
++pageout_lock_miss;
if (object->flags & OBJ_MIGHTBEDIRTY)
vnodes_skipped++;
vp = NULL;
goto unlock_and_continue;
}
VM_OBJECT_LOCK(object);
vm_page_lock(m);
vm_page_lock_queues();
/*
* The page might have been moved to another
* queue during potential blocking in vget()
* above. The page might have been freed and
* reused for another vnode.
*/
if (m->queue != PQ_INACTIVE ||
m->object != object ||
TAILQ_NEXT(m, pageq) != &marker) {
vm_page_unlock(m);
if (object->flags & OBJ_MIGHTBEDIRTY)
vnodes_skipped++;
goto unlock_and_continue;
}
/*
* The page may have been busied during the
* blocking in vget(). 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->oflags & VPO_BUSY)) {
vm_page_unlock(m);
goto unlock_and_continue;
}
/*
* If the page has become held it might
* be undergoing I/O, so skip it
*/
if (m->hold_count) {
vm_page_unlock(m);
vm_page_requeue(m);
if (object->flags & OBJ_MIGHTBEDIRTY)
vnodes_skipped++;
goto unlock_and_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.
*
* decrement page_shortage on success to account for
* the (future) cleaned page. Otherwise we could wind
* up laundering or cleaning too many pages.
*/
vm_page_unlock_queues();
if (vm_pageout_clean(m) != 0) {
--page_shortage;
--maxlaunder;
}
vm_page_lock_queues();
unlock_and_continue:
vm_page_lock_assert(m, MA_NOTOWNED);
VM_OBJECT_UNLOCK(object);
if (mp != NULL) {
vm_page_unlock_queues();
if (vp != NULL)
vput(vp);
VFS_UNLOCK_GIANT(vfslocked);
vm_object_deallocate(object);
vn_finished_write(mp);
vm_page_lock_queues();
}
next = TAILQ_NEXT(&marker, pageq);
TAILQ_REMOVE(&vm_page_queues[PQ_INACTIVE].pl,
&marker, pageq);
vm_page_lock_assert(m, MA_NOTOWNED);
continue;
}
vm_page_unlock(m);
VM_OBJECT_UNLOCK(object);
}
/*
* Compute the number of pages we want to try to move from the
* active queue to the inactive queue.
*/
page_shortage = vm_paging_target() +
cnt.v_inactive_target - cnt.v_inactive_count;
page_shortage += addl_page_shortage;
/*
* Scan the active queue for things we can deactivate. We nominally
* track the per-page activity counter and use it to locate
* deactivation candidates.
*/
pcount = cnt.v_active_count;
m = TAILQ_FIRST(&vm_page_queues[PQ_ACTIVE].pl);
mtx_assert(&vm_page_queue_mtx, MA_OWNED);
while ((m != NULL) && (pcount-- > 0) && (page_shortage > 0)) {
KASSERT(m->queue == PQ_ACTIVE,
("vm_pageout_scan: page %p isn't active", m));
next = TAILQ_NEXT(m, pageq);
if ((m->flags & PG_MARKER) != 0) {
m = next;
continue;
}
if (!vm_pageout_page_lock(m, &next)) {
vm_page_unlock(m);
m = next;
continue;
}
object = m->object;
if (!VM_OBJECT_TRYLOCK(object) &&
!vm_pageout_fallback_object_lock(m, &next)) {
VM_OBJECT_UNLOCK(object);
vm_page_unlock(m);
m = next;
continue;
}
/*
* Don't deactivate pages that are busy.
*/
if ((m->busy != 0) ||
(m->oflags & VPO_BUSY) ||
(m->hold_count != 0)) {
vm_page_unlock(m);
VM_OBJECT_UNLOCK(object);
vm_page_requeue(m);
m = next;
continue;
}
/*
* The count for pagedaemon pages is done after checking the
* page for eligibility...
*/
cnt.v_pdpages++;
/*
* Check to see "how much" the page has been used.
*/
actcount = 0;
if (object->ref_count != 0) {
if (m->aflags & PGA_REFERENCED) {
actcount += 1;
}
actcount += pmap_ts_referenced(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.
*/
vm_page_aflag_clear(m, PGA_REFERENCED);
/*
* Only if an object is currently being used, do we use the
* page activation count stats.
*/
if (actcount && (object->ref_count != 0)) {
vm_page_requeue(m);
} else {
m->act_count -= min(m->act_count, ACT_DECLINE);
if (vm_pageout_algorithm ||
object->ref_count == 0 ||
m->act_count == 0) {
page_shortage--;
if (object->ref_count == 0) {
KASSERT(!pmap_page_is_mapped(m),
("vm_pageout_scan: page %p is mapped", m));
if (m->dirty == 0)
vm_page_cache(m);
else
vm_page_deactivate(m);
} else {
vm_page_deactivate(m);
}
} else {
vm_page_requeue(m);
}
}
vm_page_unlock(m);
VM_OBJECT_UNLOCK(object);
m = next;
}
vm_page_unlock_queues();
#if !defined(NO_SWAPPING)
/*
* Idle process swapout -- run once per second.
*/
if (vm_swap_idle_enabled) {
static long lsec;
if (time_second != lsec) {
vm_req_vmdaemon(VM_SWAP_IDLE);
lsec = time_second;
}
}
#endif
/*
* 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 (vm_paging_target() > 0) {
if (vnodes_skipped && vm_page_count_min())
(void) speedup_syncer();
#if !defined(NO_SWAPPING)
if (vm_swap_enabled && vm_page_count_target())
vm_req_vmdaemon(VM_SWAP_NORMAL);
#endif
}
/*
* If we are critically low on one of RAM or swap and low on
* the other, kill the largest process. However, we avoid
* doing this on the first pass in order to give ourselves a
* chance to flush out dirty vnode-backed pages and to allow
* active pages to be moved to the inactive queue and reclaimed.
*/
if (pass != 0 &&
((swap_pager_avail < 64 && vm_page_count_min()) ||
(swap_pager_full && vm_paging_target() > 0)))
vm_pageout_oom(VM_OOM_MEM);
}
void
vm_pageout_oom(int shortage)
{
struct proc *p, *bigproc;
vm_offset_t size, bigsize;
struct thread *td;
struct vmspace *vm;
/*
* We keep the process bigproc locked once we find it to keep anyone
* from messing with it; however, there is a possibility of
* deadlock if process B is bigproc and one of it's child processes
* attempts to propagate a signal to B while we are waiting for A's
* lock while walking this list. To avoid this, we don't block on
* the process lock but just skip a process if it is already locked.
*/
bigproc = NULL;
bigsize = 0;
sx_slock(&allproc_lock);
FOREACH_PROC_IN_SYSTEM(p) {
int breakout;
if (PROC_TRYLOCK(p) == 0)
continue;
/*
* If this is a system, protected or killed process, skip it.
*/
if (p->p_state != PRS_NORMAL ||
(p->p_flag & (P_INEXEC | P_PROTECTED | P_SYSTEM)) ||
(p->p_pid == 1) || P_KILLED(p) ||
((p->p_pid < 48) && (swap_pager_avail != 0))) {
PROC_UNLOCK(p);
continue;
}
/*
* If the process is in a non-running type state,
* don't touch it. Check all the threads individually.
*/
breakout = 0;
FOREACH_THREAD_IN_PROC(p, td) {
thread_lock(td);
if (!TD_ON_RUNQ(td) &&
!TD_IS_RUNNING(td) &&
!TD_IS_SLEEPING(td) &&
!TD_IS_SUSPENDED(td)) {
thread_unlock(td);
breakout = 1;
break;
}
thread_unlock(td);
}
if (breakout) {
PROC_UNLOCK(p);
continue;
}
/*
* get the process size
*/
vm = vmspace_acquire_ref(p);
if (vm == NULL) {
PROC_UNLOCK(p);
continue;
}
if (!vm_map_trylock_read(&vm->vm_map)) {
vmspace_free(vm);
PROC_UNLOCK(p);
continue;
}
size = vmspace_swap_count(vm);
vm_map_unlock_read(&vm->vm_map);
if (shortage == VM_OOM_MEM)
size += vmspace_resident_count(vm);
vmspace_free(vm);
/*
* if the this process is bigger than the biggest one
* remember it.
*/
if (size > bigsize) {
if (bigproc != NULL)
PROC_UNLOCK(bigproc);
bigproc = p;
bigsize = size;
} else
PROC_UNLOCK(p);
}
sx_sunlock(&allproc_lock);
if (bigproc != NULL) {
killproc(bigproc, "out of swap space");
sched_nice(bigproc, PRIO_MIN);
PROC_UNLOCK(bigproc);
wakeup(&cnt.v_free_count);
}
}
/*
* 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 accumulation still occurs. This code
* helps the situation where paging just starts to occur.
*/
static void
vm_pageout_page_stats()
{
vm_object_t object;
vm_page_t m,next;
int pcount,tpcount; /* Number of pages to check */
static int fullintervalcount = 0;
int page_shortage;
page_shortage =
(cnt.v_inactive_target + cnt.v_cache_max + cnt.v_free_min) -
(cnt.v_free_count + cnt.v_inactive_count + cnt.v_cache_count);
if (page_shortage <= 0)
return;
vm_page_lock_queues();
pcount = cnt.v_active_count;
fullintervalcount += vm_pageout_stats_interval;
if (fullintervalcount < vm_pageout_full_stats_interval) {
tpcount = (int64_t)vm_pageout_stats_max * cnt.v_active_count /
cnt.v_page_count;
if (pcount > tpcount)
pcount = tpcount;
} else {
fullintervalcount = 0;
}
m = TAILQ_FIRST(&vm_page_queues[PQ_ACTIVE].pl);
while ((m != NULL) && (pcount-- > 0)) {
int actcount;
KASSERT(m->queue == PQ_ACTIVE,
("vm_pageout_page_stats: page %p isn't active", m));
next = TAILQ_NEXT(m, pageq);
if ((m->flags & PG_MARKER) != 0) {
m = next;
continue;
}
vm_page_lock_assert(m, MA_NOTOWNED);
if (!vm_pageout_page_lock(m, &next)) {
vm_page_unlock(m);
m = next;
continue;
}
object = m->object;
if (!VM_OBJECT_TRYLOCK(object) &&
!vm_pageout_fallback_object_lock(m, &next)) {
VM_OBJECT_UNLOCK(object);
vm_page_unlock(m);
m = next;
continue;
}
/*
* Don't deactivate pages that are busy.
*/
if ((m->busy != 0) ||
(m->oflags & VPO_BUSY) ||
(m->hold_count != 0)) {
vm_page_unlock(m);
VM_OBJECT_UNLOCK(object);
vm_page_requeue(m);
m = next;
continue;
}
actcount = 0;
if (m->aflags & PGA_REFERENCED) {
vm_page_aflag_clear(m, PGA_REFERENCED);
actcount += 1;
}
actcount += pmap_ts_referenced(m);
if (actcount) {
m->act_count += ACT_ADVANCE + actcount;
if (m->act_count > ACT_MAX)
m->act_count = ACT_MAX;
vm_page_requeue(m);
} 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.
*/
pmap_remove_all(m);
vm_page_deactivate(m);
} else {
m->act_count -= min(m->act_count, ACT_DECLINE);
vm_page_requeue(m);
}
}
vm_page_unlock(m);
VM_OBJECT_UNLOCK(object);
m = next;
}
vm_page_unlock_queues();
}
/*
* vm_pageout is the high level pageout daemon.
*/
static void
vm_pageout()
{
int error, pass;
/*
* Initialize some paging parameters.
*/
cnt.v_interrupt_free_min = 2;
if (cnt.v_page_count < 2000)
vm_pageout_page_count = 8;
/*
* v_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 + (cnt.v_page_count / 768);
cnt.v_free_severe = cnt.v_free_min / 2;
cnt.v_free_min += cnt.v_free_reserved;
cnt.v_free_severe += cnt.v_free_reserved;
/*
* v_free_target and v_cache_min control pageout hysteresis. Note
* that these are more a measure of the VM cache queue hysteresis
* then the VM free queue. Specifically, v_free_target is the
* high water mark (free+cache pages).
*
* v_free_reserved + v_cache_min (mostly means v_cache_min) is the
* low water mark, while v_free_min is the stop. v_cache_min must
* be big enough to handle memory needs while the pageout daemon
* is signalled and run to free more pages.
*/
if (cnt.v_free_count > 6144)
cnt.v_free_target = 4 * cnt.v_free_min + cnt.v_free_reserved;
else
cnt.v_free_target = 2 * cnt.v_free_min + cnt.v_free_reserved;
if (cnt.v_free_count > 2048) {
cnt.v_cache_min = cnt.v_free_target;
cnt.v_cache_max = 2 * cnt.v_cache_min;
cnt.v_inactive_target = (3 * cnt.v_free_target) / 2;
} else {
cnt.v_cache_min = 0;
cnt.v_cache_max = 0;
cnt.v_inactive_target = cnt.v_free_count / 4;
}
if (cnt.v_inactive_target > cnt.v_free_count / 3)
cnt.v_inactive_target = cnt.v_free_count / 3;
/* 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 = 5;
if (vm_pageout_full_stats_interval == 0)
vm_pageout_full_stats_interval = vm_pageout_stats_interval * 4;
swap_pager_swap_init();
pass = 0;
/*
* The pageout daemon is never done, so loop forever.
*/
while (TRUE) {
/*
* If we have enough free memory, wakeup waiters. Do
* not clear vm_pages_needed until we reach our target,
* otherwise we may be woken up over and over again and
* waste a lot of cpu.
*/
mtx_lock(&vm_page_queue_free_mtx);
if (vm_pages_needed && !vm_page_count_min()) {
if (!vm_paging_needed())
vm_pages_needed = 0;
wakeup(&cnt.v_free_count);
}
if (vm_pages_needed) {
/*
* Still not done, take a second pass without waiting
* (unlimited dirty cleaning), otherwise sleep a bit
* and try again.
*/
++pass;
if (pass > 1)
msleep(&vm_pages_needed,
&vm_page_queue_free_mtx, PVM, "psleep",
hz / 2);
} else {
/*
* Good enough, sleep & handle stats. Prime the pass
* for the next run.
*/
if (pass > 1)
pass = 1;
else
pass = 0;
error = msleep(&vm_pages_needed,
&vm_page_queue_free_mtx, PVM, "psleep",
vm_pageout_stats_interval * hz);
if (error && !vm_pages_needed) {
mtx_unlock(&vm_page_queue_free_mtx);
pass = 0;
vm_pageout_page_stats();
continue;
}
}
if (vm_pages_needed)
cnt.v_pdwakeups++;
mtx_unlock(&vm_page_queue_free_mtx);
vm_pageout_scan(pass);
}
}
/*
* Unless the free page queue lock is held by the caller, this function
* should be regarded as advisory. Specifically, the caller should
* not msleep() on &cnt.v_free_count following this function unless
* the free page queue lock is held until the msleep() is performed.
*/
void
pagedaemon_wakeup()
{
if (!vm_pages_needed && curthread->td_proc != pageproc) {
vm_pages_needed = 1;
wakeup(&vm_pages_needed);
}
}
#if !defined(NO_SWAPPING)
static void
vm_req_vmdaemon(int req)
{
static int lastrun = 0;
mtx_lock(&vm_daemon_mtx);
vm_pageout_req_swapout |= req;
if ((ticks > (lastrun + hz)) || (ticks < lastrun)) {
wakeup(&vm_daemon_needed);
lastrun = ticks;
}
mtx_unlock(&vm_daemon_mtx);
}
static void
vm_daemon()
{
struct rlimit rsslim;
struct proc *p;
struct thread *td;
struct vmspace *vm;
int breakout, swapout_flags, tryagain, attempts;
#ifdef RACCT
uint64_t rsize, ravailable;
#endif
while (TRUE) {
mtx_lock(&vm_daemon_mtx);
#ifdef RACCT
msleep(&vm_daemon_needed, &vm_daemon_mtx, PPAUSE, "psleep", hz);
#else
msleep(&vm_daemon_needed, &vm_daemon_mtx, PPAUSE, "psleep", 0);
#endif
swapout_flags = vm_pageout_req_swapout;
vm_pageout_req_swapout = 0;
mtx_unlock(&vm_daemon_mtx);
if (swapout_flags)
swapout_procs(swapout_flags);
/*
* scan the processes for exceeding their rlimits or if
* process is swapped out -- deactivate pages
*/
tryagain = 0;
attempts = 0;
again:
attempts++;
sx_slock(&allproc_lock);
FOREACH_PROC_IN_SYSTEM(p) {
vm_pindex_t limit, size;
/*
* if this is a system process or if we have already
* looked at this process, skip it.
*/
PROC_LOCK(p);
if (p->p_state != PRS_NORMAL ||
p->p_flag & (P_INEXEC | P_SYSTEM | P_WEXIT)) {
PROC_UNLOCK(p);
continue;
}
/*
* if the process is in a non-running type state,
* don't touch it.
*/
breakout = 0;
FOREACH_THREAD_IN_PROC(p, td) {
thread_lock(td);
if (!TD_ON_RUNQ(td) &&
!TD_IS_RUNNING(td) &&
!TD_IS_SLEEPING(td) &&
!TD_IS_SUSPENDED(td)) {
thread_unlock(td);
breakout = 1;
break;
}
thread_unlock(td);
}
if (breakout) {
PROC_UNLOCK(p);
continue;
}
/*
* get a limit
*/
lim_rlimit(p, RLIMIT_RSS, &rsslim);
limit = OFF_TO_IDX(
qmin(rsslim.rlim_cur, rsslim.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 */
vm = vmspace_acquire_ref(p);
PROC_UNLOCK(p);
if (vm == NULL)
continue;
size = vmspace_resident_count(vm);
if (limit >= 0 && size >= limit) {
vm_pageout_map_deactivate_pages(
&vm->vm_map, limit);
}
#ifdef RACCT
rsize = IDX_TO_OFF(size);
PROC_LOCK(p);
racct_set(p, RACCT_RSS, rsize);
ravailable = racct_get_available(p, RACCT_RSS);
PROC_UNLOCK(p);
if (rsize > ravailable) {
/*
* Don't be overly aggressive; this might be
* an innocent process, and the limit could've
* been exceeded by some memory hog. Don't
* try to deactivate more than 1/4th of process'
* resident set size.
*/
if (attempts <= 8) {
if (ravailable < rsize - (rsize / 4))
ravailable = rsize - (rsize / 4);
}
vm_pageout_map_deactivate_pages(
&vm->vm_map, OFF_TO_IDX(ravailable));
/* Update RSS usage after paging out. */
size = vmspace_resident_count(vm);
rsize = IDX_TO_OFF(size);
PROC_LOCK(p);
racct_set(p, RACCT_RSS, rsize);
PROC_UNLOCK(p);
if (rsize > ravailable)
tryagain = 1;
}
#endif
vmspace_free(vm);
}
sx_sunlock(&allproc_lock);
if (tryagain != 0 && attempts <= 10)
goto again;
}
}
#endif /* !defined(NO_SWAPPING) */
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