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/* $NetBSD: uvm_pdaemon.c,v 1.58 2004/01/30 11:32:16 tls 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 1.58 2004/01/30 11:32:16 tls 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 pagedaemon 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));
void 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);
/*
* The metadata cache drainer knows about uvmexp.free
* and uvmexp.freetarg. We call it _before_ scanning
* so that it sees the amount we really want.
*/
buf_drain(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);
/*
* free any cached u-areas we don't need
*/
uvm_uarea_drain(TRUE);
}
/*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
*/
void
uvmpd_scan_inactive(pglst)
struct pglist *pglst;
{
int error;
struct vm_page *p, *nextpg = NULL; /* Quell compiler warning */
struct uvm_object *uobj;
struct vm_anon *anon;
struct vm_page *swpps[round_page(MAXPHYS) >> 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 || UVM_OBJ_IS_AOBJ(uobj)) && 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();
(void) (uobj->pgops->pgo_put)(uobj, p->offset,
p->offset + PAGE_SIZE,
PGO_CLEANIT|PGO_FREE);
uvm_lock_pageq();
if (nextpg &&
(nextpg->pqflags & 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) {
int slot;
int pageidx;
pageidx = p->offset >> PAGE_SHIFT;
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;
slot = anon->an_swslot;
} else {
slot = uao_find_swslot(uobj, pageidx);
}
simple_unlock(slock);
if (slot > 0) {
/* 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.
*/
if (uvm_swapisfull()) {
dirtyreacts++;
uvm_pageactivate(p);
simple_unlock(slock);
continue;
}
/*
* start new swap pageout cluster (if necessary).
*/
if (swslot == 0) {
/* Even with strange MAXPHYS, the shift
implicitly rounds down to a page. */
swnpages = MAXPHYS >> 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);
}
}
}
/*
* 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);
pages_freed = uvmexp.pdfreed;
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.swpgavail &&
!uvm_swapisfull() &&
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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