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NetBSD/sys/uvm/uvm_pdaemon.c
chs ef57a67ca1 fix locking for loaning. in general we should be looking at the page's 
uobject and uanon pointers rather than at the PQ_ANON flag to determine
which lock to hold, since PQ_ANON can be clear even when the anon's lock
is the one which we should hold (if the page was loaned from an object
and then freed by the object).
2001-12-31 19:21:36 +00:00

883 lines
22 KiB
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/* $NetBSD: uvm_pdaemon.c,v 1.44 2001/12/31 19:21:38 chs Exp $ */
/*
* Copyright (c) 1997 Charles D. Cranor and Washington University.
* Copyright (c) 1991, 1993, The Regents of the University of California.
*
* 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 Charles D. Cranor,
* Washington University, 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.
*
* @(#)vm_pageout.c 8.5 (Berkeley) 2/14/94
* from: Id: uvm_pdaemon.c,v 1.1.2.32 1998/02/06 05:26:30 chs Exp
*
*
* Copyright (c) 1987, 1990 Carnegie-Mellon University.
* 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 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.
*/
/*
* uvm_pdaemon.c: the page daemon
*/
#include <sys/cdefs.h>
__KERNEL_RCSID(0, "$NetBSD: uvm_pdaemon.c,v 1.44 2001/12/31 19:21:38 chs Exp $");
#include "opt_uvmhist.h"
#include <sys/param.h>
#include <sys/proc.h>
#include <sys/systm.h>
#include <sys/kernel.h>
#include <sys/pool.h>
#include <sys/buf.h>
#include <sys/vnode.h>
#include <uvm/uvm.h>
/*
* UVMPD_NUMDIRTYREACTS is how many dirty pages the pagedeamon will reactivate
* in a pass thru the inactive list when swap is full. the value should be
* "small"... if it's too large we'll cycle the active pages thru the inactive
* queue too quickly to for them to be referenced and avoid being freed.
*/
#define UVMPD_NUMDIRTYREACTS 16
/*
* local prototypes
*/
void uvmpd_scan __P((void));
boolean_t uvmpd_scan_inactive __P((struct pglist *));
void uvmpd_tune __P((void));
/*
* uvm_wait: wait (sleep) for the page daemon to free some pages
*
* => should be called with all locks released
* => should _not_ be called by the page daemon (to avoid deadlock)
*/
void
uvm_wait(wmsg)
const char *wmsg;
{
int timo = 0;
int s = splbio();
/*
* check for page daemon going to sleep (waiting for itself)
*/
if (curproc == uvm.pagedaemon_proc && uvmexp.paging == 0) {
/*
* now we have a problem: the pagedaemon wants to go to
* sleep until it frees more memory. but how can it
* free more memory if it is asleep? that is a deadlock.
* we have two options:
* [1] panic now
* [2] put a timeout on the sleep, thus causing the
* pagedaemon to only pause (rather than sleep forever)
*
* note that option [2] will only help us if we get lucky
* and some other process on the system breaks the deadlock
* by exiting or freeing memory (thus allowing the pagedaemon
* to continue). for now we panic if DEBUG is defined,
* otherwise we hope for the best with option [2] (better
* yet, this should never happen in the first place!).
*/
printf("pagedaemon: deadlock detected!\n");
timo = hz >> 3; /* set timeout */
#if defined(DEBUG)
/* DEBUG: panic so we can debug it */
panic("pagedaemon deadlock");
#endif
}
simple_lock(&uvm.pagedaemon_lock);
wakeup(&uvm.pagedaemon); /* wake the daemon! */
UVM_UNLOCK_AND_WAIT(&uvmexp.free, &uvm.pagedaemon_lock, FALSE, wmsg,
timo);
splx(s);
}
/*
* uvmpd_tune: tune paging parameters
*
* => called when ever memory is added (or removed?) to the system
* => caller must call with page queues locked
*/
void
uvmpd_tune(void)
{
UVMHIST_FUNC("uvmpd_tune"); UVMHIST_CALLED(pdhist);
uvmexp.freemin = uvmexp.npages / 20;
/* between 16k and 256k */
/* XXX: what are these values good for? */
uvmexp.freemin = MAX(uvmexp.freemin, (16*1024) >> PAGE_SHIFT);
uvmexp.freemin = MIN(uvmexp.freemin, (256*1024) >> PAGE_SHIFT);
/* Make sure there's always a user page free. */
if (uvmexp.freemin < uvmexp.reserve_kernel + 1)
uvmexp.freemin = uvmexp.reserve_kernel + 1;
uvmexp.freetarg = (uvmexp.freemin * 4) / 3;
if (uvmexp.freetarg <= uvmexp.freemin)
uvmexp.freetarg = uvmexp.freemin + 1;
/* uvmexp.inactarg: computed in main daemon loop */
uvmexp.wiredmax = uvmexp.npages / 3;
UVMHIST_LOG(pdhist, "<- done, freemin=%d, freetarg=%d, wiredmax=%d",
uvmexp.freemin, uvmexp.freetarg, uvmexp.wiredmax, 0);
}
/*
* uvm_pageout: the main loop for the pagedaemon
*/
void
uvm_pageout(void *arg)
{
int npages = 0;
UVMHIST_FUNC("uvm_pageout"); UVMHIST_CALLED(pdhist);
UVMHIST_LOG(pdhist,"<starting uvm pagedaemon>", 0, 0, 0, 0);
/*
* ensure correct priority and set paging parameters...
*/
uvm.pagedaemon_proc = curproc;
uvm_lock_pageq();
npages = uvmexp.npages;
uvmpd_tune();
uvm_unlock_pageq();
/*
* main loop
*/
for (;;) {
simple_lock(&uvm.pagedaemon_lock);
UVMHIST_LOG(pdhist," <<SLEEPING>>",0,0,0,0);
UVM_UNLOCK_AND_WAIT(&uvm.pagedaemon,
&uvm.pagedaemon_lock, FALSE, "pgdaemon", 0);
uvmexp.pdwoke++;
UVMHIST_LOG(pdhist," <<WOKE UP>>",0,0,0,0);
/*
* now lock page queues and recompute inactive count
*/
uvm_lock_pageq();
if (npages != uvmexp.npages) { /* check for new pages? */
npages = uvmexp.npages;
uvmpd_tune();
}
uvmexp.inactarg = (uvmexp.active + uvmexp.inactive) / 3;
if (uvmexp.inactarg <= uvmexp.freetarg) {
uvmexp.inactarg = uvmexp.freetarg + 1;
}
UVMHIST_LOG(pdhist," free/ftarg=%d/%d, inact/itarg=%d/%d",
uvmexp.free, uvmexp.freetarg, uvmexp.inactive,
uvmexp.inactarg);
/*
* scan if needed
*/
if (uvmexp.free + uvmexp.paging < uvmexp.freetarg ||
uvmexp.inactive < uvmexp.inactarg) {
uvmpd_scan();
}
/*
* if there's any free memory to be had,
* wake up any waiters.
*/
if (uvmexp.free > uvmexp.reserve_kernel ||
uvmexp.paging == 0) {
wakeup(&uvmexp.free);
}
/*
* scan done. unlock page queues (the only lock we are holding)
*/
uvm_unlock_pageq();
/*
* drain pool resources now that we're not holding any locks
*/
pool_drain(0);
}
/*NOTREACHED*/
}
/*
* uvm_aiodone_daemon: main loop for the aiodone daemon.
*/
void
uvm_aiodone_daemon(void *arg)
{
int s, free;
struct buf *bp, *nbp;
UVMHIST_FUNC("uvm_aiodoned"); UVMHIST_CALLED(pdhist);
for (;;) {
/*
* carefully attempt to go to sleep (without losing "wakeups"!).
* we need splbio because we want to make sure the aio_done list
* is totally empty before we go to sleep.
*/
s = splbio();
simple_lock(&uvm.aiodoned_lock);
if (TAILQ_FIRST(&uvm.aio_done) == NULL) {
UVMHIST_LOG(pdhist," <<SLEEPING>>",0,0,0,0);
UVM_UNLOCK_AND_WAIT(&uvm.aiodoned,
&uvm.aiodoned_lock, FALSE, "aiodoned", 0);
UVMHIST_LOG(pdhist," <<WOKE UP>>",0,0,0,0);
/* relock aiodoned_lock, still at splbio */
simple_lock(&uvm.aiodoned_lock);
}
/*
* check for done aio structures
*/
bp = TAILQ_FIRST(&uvm.aio_done);
if (bp) {
TAILQ_INIT(&uvm.aio_done);
}
simple_unlock(&uvm.aiodoned_lock);
splx(s);
/*
* process each i/o that's done.
*/
free = uvmexp.free;
while (bp != NULL) {
nbp = TAILQ_NEXT(bp, b_freelist);
(*bp->b_iodone)(bp);
bp = nbp;
}
if (free <= uvmexp.reserve_kernel) {
s = uvm_lock_fpageq();
wakeup(&uvm.pagedaemon);
uvm_unlock_fpageq(s);
} else {
simple_lock(&uvm.pagedaemon_lock);
wakeup(&uvmexp.free);
simple_unlock(&uvm.pagedaemon_lock);
}
}
}
/*
* uvmpd_scan_inactive: scan an inactive list for pages to clean or free.
*
* => called with page queues locked
* => we work on meeting our free target by converting inactive pages
* into free pages.
* => we handle the building of swap-backed clusters
* => we return TRUE if we are exiting because we met our target
*/
boolean_t
uvmpd_scan_inactive(pglst)
struct pglist *pglst;
{
int error;
struct vm_page *p, *nextpg;
struct uvm_object *uobj;
struct vm_anon *anon;
struct vm_page *swpps[MAXBSIZE >> PAGE_SHIFT];
struct simplelock *slock;
int swnpages, swcpages;
int swslot;
int dirtyreacts, t, result;
boolean_t anonunder, fileunder, execunder;
boolean_t anonover, fileover, execover;
boolean_t anonreact, filereact, execreact;
UVMHIST_FUNC("uvmpd_scan_inactive"); UVMHIST_CALLED(pdhist);
/*
* swslot is non-zero if we are building a swap cluster. we want
* to stay in the loop while we have a page to scan or we have
* a swap-cluster to build.
*/
swslot = 0;
swnpages = swcpages = 0;
dirtyreacts = 0;
/*
* decide which types of pages we want to reactivate instead of freeing
* to keep usage within the minimum and maximum usage limits.
*/
t = uvmexp.active + uvmexp.inactive + uvmexp.free;
anonunder = (uvmexp.anonpages <= (t * uvmexp.anonmin) >> 8);
fileunder = (uvmexp.filepages <= (t * uvmexp.filemin) >> 8);
execunder = (uvmexp.execpages <= (t * uvmexp.execmin) >> 8);
anonover = uvmexp.anonpages > ((t * uvmexp.anonmax) >> 8);
fileover = uvmexp.filepages > ((t * uvmexp.filemax) >> 8);
execover = uvmexp.execpages > ((t * uvmexp.execmax) >> 8);
anonreact = anonunder || (!anonover && (fileover || execover));
filereact = fileunder || (!fileover && (anonover || execover));
execreact = execunder || (!execover && (anonover || fileover));
for (p = TAILQ_FIRST(pglst); p != NULL || swslot != 0; p = nextpg) {
uobj = NULL;
anon = NULL;
if (p) {
/*
* see if we've met the free target.
*/
if (uvmexp.free + uvmexp.paging >=
uvmexp.freetarg << 2 ||
dirtyreacts == UVMPD_NUMDIRTYREACTS) {
UVMHIST_LOG(pdhist," met free target: "
"exit loop", 0, 0, 0, 0);
if (swslot == 0) {
/* exit now if no swap-i/o pending */
break;
}
/* set p to null to signal final swap i/o */
p = NULL;
nextpg = NULL;
}
}
if (p) { /* if (we have a new page to consider) */
/*
* we are below target and have a new page to consider.
*/
uvmexp.pdscans++;
nextpg = TAILQ_NEXT(p, pageq);
/*
* move referenced pages back to active queue and
* skip to next page.
*/
if (pmap_clear_reference(p)) {
uvm_pageactivate(p);
uvmexp.pdreact++;
continue;
}
anon = p->uanon;
uobj = p->uobject;
/*
* enforce the minimum thresholds on different
* types of memory usage. if reusing the current
* page would reduce that type of usage below its
* minimum, reactivate the page instead and move
* on to the next page.
*/
if (uobj && UVM_OBJ_IS_VTEXT(uobj) && execreact) {
uvm_pageactivate(p);
uvmexp.pdreexec++;
continue;
}
if (uobj && UVM_OBJ_IS_VNODE(uobj) &&
!UVM_OBJ_IS_VTEXT(uobj) && filereact) {
uvm_pageactivate(p);
uvmexp.pdrefile++;
continue;
}
if (anon && anonreact) {
uvm_pageactivate(p);
uvmexp.pdreanon++;
continue;
}
/*
* first we attempt to lock the object that this page
* belongs to. if our attempt fails we skip on to
* the next page (no harm done). it is important to
* "try" locking the object as we are locking in the
* wrong order (pageq -> object) and we don't want to
* deadlock.
*
* the only time we expect to see an ownerless page
* (i.e. a page with no uobject and !PQ_ANON) is if an
* anon has loaned a page from a uvm_object and the
* uvm_object has dropped the ownership. in that
* case, the anon can "take over" the loaned page
* and make it its own.
*/
/* does the page belong to an object? */
if (uobj != NULL) {
slock = &uobj->vmobjlock;
if (!simple_lock_try(slock)) {
continue;
}
if (p->flags & PG_BUSY) {
simple_unlock(slock);
uvmexp.pdbusy++;
continue;
}
uvmexp.pdobscan++;
} else {
KASSERT(anon != NULL);
slock = &anon->an_lock;
if (!simple_lock_try(slock)) {
continue;
}
/*
* set PQ_ANON if it isn't set already.
*/
if ((p->pqflags & PQ_ANON) == 0) {
KASSERT(p->loan_count > 0);
p->loan_count--;
p->pqflags |= PQ_ANON;
/* anon now owns it */
}
if (p->flags & PG_BUSY) {
simple_unlock(slock);
uvmexp.pdbusy++;
continue;
}
uvmexp.pdanscan++;
}
/*
* we now have the object and the page queues locked.
* if the page is not swap-backed, call the object's
* pager to flush and free the page.
*/
if ((p->pqflags & PQ_SWAPBACKED) == 0) {
uvm_unlock_pageq();
error = (uobj->pgops->pgo_put)(uobj, p->offset,
p->offset + PAGE_SIZE,
PGO_CLEANIT|PGO_FREE);
uvm_lock_pageq();
if (nextpg &&
(nextpg->flags & PQ_INACTIVE) == 0) {
nextpg = TAILQ_FIRST(pglst);
}
continue;
}
/*
* the page is swap-backed. remove all the permissions
* from the page so we can sync the modified info
* without any race conditions. if the page is clean
* we can free it now and continue.
*/
pmap_page_protect(p, VM_PROT_NONE);
if ((p->flags & PG_CLEAN) && pmap_clear_modify(p)) {
p->flags &= ~(PG_CLEAN);
}
if (p->flags & PG_CLEAN) {
uvm_pagefree(p);
uvmexp.pdfreed++;
/*
* for anons, we need to remove the page
* from the anon ourselves. for aobjs,
* pagefree did that for us.
*/
if (anon) {
KASSERT(anon->an_swslot != 0);
anon->u.an_page = NULL;
}
simple_unlock(slock);
/* this page is now only in swap. */
simple_lock(&uvm.swap_data_lock);
KASSERT(uvmexp.swpgonly < uvmexp.swpginuse);
uvmexp.swpgonly++;
simple_unlock(&uvm.swap_data_lock);
continue;
}
/*
* this page is dirty, skip it if we'll have met our
* free target when all the current pageouts complete.
*/
if (uvmexp.free + uvmexp.paging >
uvmexp.freetarg << 2) {
simple_unlock(slock);
continue;
}
/*
* free any swap space allocated to the page since
* we'll have to write it again with its new data.
*/
if ((p->pqflags & PQ_ANON) && anon->an_swslot) {
uvm_swap_free(anon->an_swslot, 1);
anon->an_swslot = 0;
} else if (p->pqflags & PQ_AOBJ) {
uao_dropswap(uobj, p->offset >> PAGE_SHIFT);
}
/*
* if all pages in swap are only in swap,
* the swap space is full and we can't page out
* any more swap-backed pages. reactivate this page
* so that we eventually cycle all pages through
* the inactive queue.
*/
KASSERT(uvmexp.swpgonly <= uvmexp.swpages);
if (uvmexp.swpgonly == uvmexp.swpages) {
dirtyreacts++;
uvm_pageactivate(p);
simple_unlock(slock);
continue;
}
/*
* start new swap pageout cluster (if necessary).
*/
if (swslot == 0) {
swnpages = MAXBSIZE >> PAGE_SHIFT;
swslot = uvm_swap_alloc(&swnpages, TRUE);
if (swslot == 0) {
simple_unlock(slock);
continue;
}
swcpages = 0;
}
/*
* at this point, we're definitely going reuse this
* page. mark the page busy and delayed-free.
* we should remove the page from the page queues
* so we don't ever look at it again.
* adjust counters and such.
*/
p->flags |= PG_BUSY;
UVM_PAGE_OWN(p, "scan_inactive");
p->flags |= PG_PAGEOUT;
uvmexp.paging++;
uvm_pagedequeue(p);
uvmexp.pgswapout++;
/*
* add the new page to the cluster.
*/
if (anon) {
anon->an_swslot = swslot + swcpages;
simple_unlock(slock);
} else {
result = uao_set_swslot(uobj,
p->offset >> PAGE_SHIFT, swslot + swcpages);
if (result == -1) {
p->flags &= ~(PG_BUSY|PG_PAGEOUT);
UVM_PAGE_OWN(p, NULL);
uvmexp.paging--;
uvm_pageactivate(p);
simple_unlock(slock);
continue;
}
simple_unlock(slock);
}
swpps[swcpages] = p;
swcpages++;
/*
* if the cluster isn't full, look for more pages
* before starting the i/o.
*/
if (swcpages < swnpages) {
continue;
}
}
/*
* if this is the final pageout we could have a few
* unused swap blocks. if so, free them now.
*/
if (swcpages < swnpages) {
uvm_swap_free(swslot + swcpages, (swnpages - swcpages));
}
/*
* now start the pageout.
*/
uvm_unlock_pageq();
uvmexp.pdpageouts++;
error = uvm_swap_put(swslot, swpps, swcpages, 0);
KASSERT(error == 0);
uvm_lock_pageq();
/*
* zero swslot to indicate that we are
* no longer building a swap-backed cluster.
*/
swslot = 0;
/*
* the pageout is in progress. bump counters and set up
* for the next loop.
*/
uvmexp.pdpending++;
if (nextpg && (nextpg->pqflags & PQ_INACTIVE) == 0) {
nextpg = TAILQ_FIRST(pglst);
}
}
return (error);
}
/*
* uvmpd_scan: scan the page queues and attempt to meet our targets.
*
* => called with pageq's locked
*/
void
uvmpd_scan(void)
{
int inactive_shortage, swap_shortage, pages_freed;
struct vm_page *p, *nextpg;
struct uvm_object *uobj;
struct vm_anon *anon;
struct simplelock *slock;
UVMHIST_FUNC("uvmpd_scan"); UVMHIST_CALLED(pdhist);
uvmexp.pdrevs++;
uobj = NULL;
anon = NULL;
#ifndef __SWAP_BROKEN
/*
* swap out some processes if we are below our free target.
* we need to unlock the page queues for this.
*/
if (uvmexp.free < uvmexp.freetarg && uvmexp.nswapdev != 0) {
uvmexp.pdswout++;
UVMHIST_LOG(pdhist," free %d < target %d: swapout",
uvmexp.free, uvmexp.freetarg, 0, 0);
uvm_unlock_pageq();
uvm_swapout_threads();
uvm_lock_pageq();
}
#endif
/*
* now we want to work on meeting our targets. first we work on our
* free target by converting inactive pages into free pages. then
* we work on meeting our inactive target by converting active pages
* to inactive ones.
*/
UVMHIST_LOG(pdhist, " starting 'free' loop",0,0,0,0);
/*
* alternate starting queue between swap and object based on the
* low bit of uvmexp.pdrevs (which we bump by one each call).
*/
pages_freed = uvmexp.pdfreed;
(void) uvmpd_scan_inactive(&uvm.page_inactive);
pages_freed = uvmexp.pdfreed - pages_freed;
/*
* we have done the scan to get free pages. now we work on meeting
* our inactive target.
*/
inactive_shortage = uvmexp.inactarg - uvmexp.inactive;
/*
* detect if we're not going to be able to page anything out
* until we free some swap resources from active pages.
*/
swap_shortage = 0;
if (uvmexp.free < uvmexp.freetarg &&
uvmexp.swpginuse == uvmexp.swpages &&
uvmexp.swpgonly < uvmexp.swpages &&
pages_freed == 0) {
swap_shortage = uvmexp.freetarg - uvmexp.free;
}
UVMHIST_LOG(pdhist, " loop 2: inactive_shortage=%d swap_shortage=%d",
inactive_shortage, swap_shortage,0,0);
for (p = TAILQ_FIRST(&uvm.page_active);
p != NULL && (inactive_shortage > 0 || swap_shortage > 0);
p = nextpg) {
nextpg = TAILQ_NEXT(p, pageq);
if (p->flags & PG_BUSY) {
continue;
}
/*
* lock the page's owner.
*/
if (p->uobject != NULL) {
uobj = p->uobject;
slock = &uobj->vmobjlock;
if (!simple_lock_try(slock)) {
continue;
}
} else {
anon = p->uanon;
KASSERT(anon != NULL);
slock = &anon->an_lock;
if (!simple_lock_try(slock)) {
continue;
}
/* take over the page? */
if ((p->pqflags & PQ_ANON) == 0) {
KASSERT(p->loan_count > 0);
p->loan_count--;
p->pqflags |= PQ_ANON;
}
}
/*
* skip this page if it's busy.
*/
if ((p->flags & PG_BUSY) != 0) {
simple_unlock(slock);
continue;
}
/*
* if there's a shortage of swap, free any swap allocated
* to this page so that other pages can be paged out.
*/
if (swap_shortage > 0) {
if ((p->pqflags & PQ_ANON) && anon->an_swslot) {
uvm_swap_free(anon->an_swslot, 1);
anon->an_swslot = 0;
p->flags &= ~PG_CLEAN;
swap_shortage--;
} else if (p->pqflags & PQ_AOBJ) {
int slot = uao_set_swslot(uobj,
p->offset >> PAGE_SHIFT, 0);
if (slot) {
uvm_swap_free(slot, 1);
p->flags &= ~PG_CLEAN;
swap_shortage--;
}
}
}
/*
* if there's a shortage of inactive pages, deactivate.
*/
if (inactive_shortage > 0) {
/* no need to check wire_count as pg is "active" */
uvm_pagedeactivate(p);
uvmexp.pddeact++;
inactive_shortage--;
}
/*
* we're done with this page.
*/
simple_unlock(slock);
}
}
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