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NetBSD/sys/uvm/uvm_pdaemon.c
thorpej 6eb9ee7cd8 - Change uvm_{lock,unlock}_fpageq() to return/take the previous interrupt 
level directly, instead of making the caller wrap the calls in
  splimp()/splx().
- Add a comment documenting that interrupts that cause memory allocation
  must be blocked while the free page queue is locked.

Since interrupts must be blocked while this lock is asserted, tying them
together like this helps to prevent mistakes.
1999-05-24 19:10:57 +00:00

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/* $NetBSD: uvm_pdaemon.c,v 1.16 1999/05/24 19:10:57 thorpej 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.
*/
#include "opt_uvmhist.h"
/*
* uvm_pdaemon.c: the page daemon
*/
#include <sys/param.h>
#include <sys/proc.h>
#include <sys/systm.h>
#include <sys/kernel.h>
#include <sys/pool.h>
#include <vm/vm.h>
#include <vm/vm_page.h>
#include <vm/vm_kern.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
*/
static void uvmpd_scan __P((void));
static boolean_t uvmpd_scan_inactive __P((struct pglist *));
static 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)
char *wmsg;
{
int timo = 0;
int s = splbio();
/*
* check for page daemon going to sleep (waiting for itself)
*/
if (curproc == uvm.pagedaemon_proc) {
/*
* 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);
thread_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
*/
static void
uvmpd_tune()
{
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);
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()
{
int npages = 0;
int s;
struct uvm_aiodesc *aio, *nextaio;
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;
(void) spl0();
uvm_lock_pageq();
npages = uvmexp.npages;
uvmpd_tune();
uvm_unlock_pageq();
/*
* main loop
*/
while (TRUE) {
/*
* 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.pagedaemon_lock);
/*
* if we've got done aio's, then bypass the sleep
*/
if (uvm.aio_done.tqh_first == NULL) {
UVMHIST_LOG(maphist," <<SLEEPING>>",0,0,0,0);
UVM_UNLOCK_AND_WAIT(&uvm.pagedaemon,
&uvm.pagedaemon_lock, FALSE, "daemon_slp", 0);
uvmexp.pdwoke++;
UVMHIST_LOG(pdhist," <<WOKE UP>>",0,0,0,0);
/* relock pagedaemon_lock, still at splbio */
simple_lock(&uvm.pagedaemon_lock);
}
/*
* check for done aio structures
*/
aio = uvm.aio_done.tqh_first; /* save current list (if any)*/
if (aio) {
TAILQ_INIT(&uvm.aio_done); /* zero global list */
}
simple_unlock(&uvm.pagedaemon_lock); /* unlock */
splx(s); /* drop splbio */
/*
* first clear out any pending aios (to free space in case we
* want to pageout more stuff).
*/
for (/*null*/; aio != NULL ; aio = nextaio) {
uvmexp.paging -= aio->npages;
nextaio = aio->aioq.tqe_next;
aio->aiodone(aio);
}
/* Next, drain pool resources */
pool_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
* [XXX: note we are reading uvm.free without locking]
*/
if (uvmexp.free < uvmexp.freetarg ||
uvmexp.inactive < uvmexp.inactarg)
uvmpd_scan();
/*
* done scan. unlock page queues (the only lock we are holding)
*/
uvm_unlock_pageq();
/*
* done! restart loop.
*/
if (uvmexp.free > uvmexp.reserve_kernel ||
uvmexp.paging == 0)
thread_wakeup(&uvmexp.free);
}
/*NOTREACHED*/
}
/*
* uvmpd_scan_inactive: the first loop of uvmpd_scan broken out into
* its own function for ease of reading.
*
* => 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
*/
static boolean_t
uvmpd_scan_inactive(pglst)
struct pglist *pglst;
{
boolean_t retval = FALSE; /* assume we haven't hit target */
int s, free, result;
struct vm_page *p, *nextpg;
struct uvm_object *uobj;
struct vm_page *pps[MAXBSIZE >> PAGE_SHIFT], **ppsp;
int npages;
struct vm_page *swpps[MAXBSIZE >> PAGE_SHIFT]; /* XXX: see below */
int swnpages, swcpages; /* XXX: see below */
int swslot;
struct vm_anon *anon;
boolean_t swap_backed;
vaddr_t start;
int dirtyreacts;
UVMHIST_FUNC("uvmpd_scan_inactive"); UVMHIST_CALLED(pdhist);
/*
* note: we currently keep swap-backed pages on a seperate inactive
* list from object-backed pages. however, merging the two lists
* back together again hasn't been ruled out. thus, we keep our
* swap cluster in "swpps" rather than in pps (allows us to mix
* clustering types in the event of a mixed inactive queue).
*/
/*
* 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;
free = 0;
dirtyreacts = 0;
for (p = pglst->tqh_first ; p != NULL || swslot != 0 ; p = nextpg) {
/*
* note that p can be NULL iff we have traversed the whole
* list and need to do one final swap-backed clustered pageout.
*/
if (p) {
/*
* update our copy of "free" and see if we've met
* our target
*/
s = uvm_lock_fpageq();
free = uvmexp.free;
uvm_unlock_fpageq(s);
if (free + uvmexp.paging >= uvmexp.freetarg << 2 ||
dirtyreacts == UVMPD_NUMDIRTYREACTS) {
UVMHIST_LOG(pdhist," met free target: "
"exit loop", 0, 0, 0, 0);
retval = TRUE; /* hit the target! */
if (swslot == 0)
/* exit now if no swap-i/o pending */
break;
/* set p to null to signal final swap i/o */
p = NULL;
}
}
uobj = NULL; /* be safe and shut gcc up */
anon = NULL; /* be safe and shut gcc up */
if (p) { /* if (we have a new page to consider) */
/*
* we are below target and have a new page to consider.
*/
uvmexp.pdscans++;
nextpg = p->pageq.tqe_next;
/*
* move referenced pages back to active queue and
* skip to next page (unlikely to happen since
* inactive pages shouldn't have any valid mappings
* and we cleared reference before deactivating).
*/
if (pmap_is_referenced(PMAP_PGARG(p))) {
uvm_pageactivate(p);
uvmexp.pdreact++;
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
* get deadlocked.
*
* the only time we exepct 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.
*/
/* is page part of an anon or ownerless ? */
if ((p->pqflags & PQ_ANON) || p->uobject == NULL) {
anon = p->uanon;
#ifdef DIAGNOSTIC
/* to be on inactive q, page must be part
* of _something_ */
if (anon == NULL)
panic("pagedaemon: page with no anon "
"or object detected - loop 1");
#endif
if (!simple_lock_try(&anon->an_lock))
/* lock failed, skip this page */
continue;
/*
* if the page is ownerless, claim it in the
* name of "anon"!
*/
if ((p->pqflags & PQ_ANON) == 0) {
#ifdef DIAGNOSTIC
if (p->loan_count < 1)
panic("pagedaemon: non-loaned "
"ownerless page detected -"
" loop 1");
#endif
p->loan_count--;
p->pqflags |= PQ_ANON; /* anon now owns it */
}
if (p->flags & PG_BUSY) {
simple_unlock(&anon->an_lock);
uvmexp.pdbusy++;
/* someone else owns page, skip it */
continue;
}
uvmexp.pdanscan++;
} else {
uobj = p->uobject;
if (!simple_lock_try(&uobj->vmobjlock))
/* lock failed, skip this page */
continue;
if (p->flags & PG_BUSY) {
simple_unlock(&uobj->vmobjlock);
uvmexp.pdbusy++;
/* someone else owns page, skip it */
continue;
}
uvmexp.pdobscan++;
}
/*
* we now have the object and the page queues locked.
* the page is not busy. if the page is clean we
* can free it now and continue.
*/
if (p->flags & PG_CLEAN) {
if (p->pqflags & PQ_SWAPBACKED) {
/* this page now lives only in swap */
simple_lock(&uvm.swap_data_lock);
uvmexp.swpgonly++;
simple_unlock(&uvm.swap_data_lock);
}
/* zap all mappings with pmap_page_protect... */
pmap_page_protect(PMAP_PGARG(p), VM_PROT_NONE);
uvm_pagefree(p);
uvmexp.pdfreed++;
if (anon) {
#ifdef DIAGNOSTIC
/*
* an anonymous page can only be clean
* if it has valid backing store.
*/
if (anon->an_swslot == 0)
panic("pagedaemon: clean anon "
"page without backing store?");
#endif
/* remove from object */
anon->u.an_page = NULL;
simple_unlock(&anon->an_lock);
} else {
/* pagefree has already removed the
* page from the object */
simple_unlock(&uobj->vmobjlock);
}
continue;
}
/*
* this page is dirty, skip it if we'll have met our
* free target when all the current pageouts complete.
*/
if (free + uvmexp.paging > uvmexp.freetarg << 2) {
if (anon) {
simple_unlock(&anon->an_lock);
} else {
simple_unlock(&uobj->vmobjlock);
}
continue;
}
/*
* this page is dirty, but we can't page it out
* since all pages in swap are only in swap.
* reactivate it so that we eventually cycle
* all pages thru the inactive queue.
*/
#ifdef DIAGNOSTIC
if (uvmexp.swpgonly > uvmexp.swpages) {
panic("uvmexp.swpgonly botch");
}
#endif
if ((p->pqflags & PQ_SWAPBACKED) &&
uvmexp.swpgonly == uvmexp.swpages) {
dirtyreacts++;
uvm_pageactivate(p);
if (anon) {
simple_unlock(&anon->an_lock);
} else {
simple_unlock(&uobj->vmobjlock);
}
continue;
}
/*
* if the page is swap-backed and dirty and swap space
* is full, free any swap allocated to the page
* so that other pages can be paged out.
*/
#ifdef DIAGNOSTIC
if (uvmexp.swpginuse > uvmexp.swpages) {
panic("uvmexp.swpginuse botch");
}
#endif
if ((p->pqflags & PQ_SWAPBACKED) &&
uvmexp.swpginuse == uvmexp.swpages) {
if ((p->pqflags & PQ_ANON) &&
p->uanon->an_swslot) {
uvm_swap_free(p->uanon->an_swslot, 1);
p->uanon->an_swslot = 0;
}
if (p->pqflags & PQ_AOBJ) {
uao_dropswap(p->uobject,
p->offset >> PAGE_SHIFT);
}
}
/*
* the page we are looking at is dirty. we must
* clean it before it can be freed. to do this we
* first mark the page busy so that no one else will
* touch the page. we write protect all the mappings
* of the page so that no one touches it while it is
* in I/O.
*/
swap_backed = ((p->pqflags & PQ_SWAPBACKED) != 0);
p->flags |= PG_BUSY; /* now we own it */
UVM_PAGE_OWN(p, "scan_inactive");
pmap_page_protect(PMAP_PGARG(p), VM_PROT_READ);
uvmexp.pgswapout++;
/*
* for swap-backed pages we need to (re)allocate
* swap space.
*/
if (swap_backed) {
/*
* free old swap slot (if any)
*/
if (anon) {
if (anon->an_swslot) {
uvm_swap_free(anon->an_swslot,
1);
anon->an_swslot = 0;
}
} else {
uao_dropswap(uobj,
p->offset >> PAGE_SHIFT);
}
/*
* start new cluster (if necessary)
*/
if (swslot == 0) {
/* want this much */
swnpages = MAXBSIZE >> PAGE_SHIFT;
swslot = uvm_swap_alloc(&swnpages,
TRUE);
if (swslot == 0) {
/* no swap? give up! */
p->flags &= ~PG_BUSY;
UVM_PAGE_OWN(p, NULL);
if (anon)
simple_unlock(
&anon->an_lock);
else
simple_unlock(
&uobj->vmobjlock);
continue;
}
swcpages = 0; /* cluster is empty */
}
/*
* add block to cluster
*/
swpps[swcpages] = p;
if (anon)
anon->an_swslot = swslot + swcpages;
else
uao_set_swslot(uobj,
p->offset >> PAGE_SHIFT,
swslot + swcpages);
swcpages++;
/* done (swap-backed) */
}
/* end: if (p) ["if we have new page to consider"] */
} else {
/* if p == NULL we must be doing a last swap i/o */
swap_backed = TRUE;
}
/*
* now consider doing the pageout.
*
* for swap-backed pages, we do the pageout if we have either
* filled the cluster (in which case (swnpages == swcpages) or
* run out of pages (p == NULL).
*
* for object pages, we always do the pageout.
*/
if (swap_backed) {
if (p) { /* if we just added a page to cluster */
if (anon)
simple_unlock(&anon->an_lock);
else
simple_unlock(&uobj->vmobjlock);
/* cluster not full yet? */
if (swcpages < swnpages)
continue;
}
/* starting I/O now... set up for it */
npages = swcpages;
ppsp = swpps;
/* for swap-backed pages only */
start = (vaddr_t) swslot;
/* if this is final pageout we could have a few
* extra swap blocks */
if (swcpages < swnpages) {
uvm_swap_free(swslot + swcpages,
(swnpages - swcpages));
}
} else {
/* normal object pageout */
ppsp = pps;
npages = sizeof(pps) / sizeof(struct vm_page *);
/* not looked at because PGO_ALLPAGES is set */
start = 0;
}
/*
* now do the pageout.
*
* for swap_backed pages we have already built the cluster.
* for !swap_backed pages, uvm_pager_put will call the object's
* "make put cluster" function to build a cluster on our behalf.
*
* we pass the PGO_PDFREECLUST flag to uvm_pager_put to instruct
* it to free the cluster pages for us on a successful I/O (it
* always does this for un-successful I/O requests). this
* allows us to do clustered pageout without having to deal
* with cluster pages at this level.
*
* note locking semantics of uvm_pager_put with PGO_PDFREECLUST:
* IN: locked: uobj (if !swap_backed), page queues
* OUT: locked: uobj (if !swap_backed && result !=VM_PAGER_PEND)
* !locked: pageqs, uobj (if swap_backed || VM_PAGER_PEND)
*
* [the bit about VM_PAGER_PEND saves us one lock-unlock pair]
*/
/* locked: uobj (if !swap_backed), page queues */
uvmexp.pdpageouts++;
result = uvm_pager_put((swap_backed) ? NULL : uobj, p,
&ppsp, &npages, PGO_ALLPAGES|PGO_PDFREECLUST, start, 0);
/* locked: uobj (if !swap_backed && result != PEND) */
/* unlocked: pageqs, object (if swap_backed ||result == PEND) */
/*
* if we did i/o to swap, zero swslot to indicate that we are
* no longer building a swap-backed cluster.
*/
if (swap_backed)
swslot = 0; /* done with this cluster */
/*
* first, we check for VM_PAGER_PEND which means that the
* async I/O is in progress and the async I/O done routine
* will clean up after us. in this case we move on to the
* next page.
*
* there is a very remote chance that the pending async i/o can
* finish _before_ we get here. if that happens, our page "p"
* may no longer be on the inactive queue. so we verify this
* when determining the next page (starting over at the head if
* we've lost our inactive page).
*/
if (result == VM_PAGER_PEND) {
uvmexp.paging += npages;
uvm_lock_pageq(); /* relock page queues */
uvmexp.pdpending++;
if (p) {
if (p->pqflags & PQ_INACTIVE)
/* reload! */
nextpg = p->pageq.tqe_next;
else
/* reload! */
nextpg = pglst->tqh_first;
} else {
nextpg = NULL; /* done list */
}
continue;
}
/*
* clean up "p" if we have one
*/
if (p) {
/*
* the I/O request to "p" is done and uvm_pager_put
* has freed any cluster pages it may have allocated
* during I/O. all that is left for us to do is
* clean up page "p" (which is still PG_BUSY).
*
* our result could be one of the following:
* VM_PAGER_OK: successful pageout
*
* VM_PAGER_AGAIN: tmp resource shortage, we skip
* to next page
* VM_PAGER_{FAIL,ERROR,BAD}: an error. we
* "reactivate" page to get it out of the way (it
* will eventually drift back into the inactive
* queue for a retry).
* VM_PAGER_UNLOCK: should never see this as it is
* only valid for "get" operations
*/
/* relock p's object: page queues not lock yet, so
* no need for "try" */
/* !swap_backed case: already locked... */
if (swap_backed) {
if (anon)
simple_lock(&anon->an_lock);
else
simple_lock(&uobj->vmobjlock);
}
#ifdef DIAGNOSTIC
if (result == VM_PAGER_UNLOCK)
panic("pagedaemon: pageout returned "
"invalid 'unlock' code");
#endif
/* handle PG_WANTED now */
if (p->flags & PG_WANTED)
/* still holding object lock */
thread_wakeup(p);
p->flags &= ~(PG_BUSY|PG_WANTED);
UVM_PAGE_OWN(p, NULL);
/* released during I/O? */
if (p->flags & PG_RELEASED) {
if (anon) {
/* remove page so we can get nextpg */
anon->u.an_page = NULL;
simple_unlock(&anon->an_lock);
uvm_anfree(anon); /* kills anon */
pmap_page_protect(PMAP_PGARG(p),
VM_PROT_NONE);
anon = NULL;
uvm_lock_pageq();
nextpg = p->pageq.tqe_next;
/* free released page */
uvm_pagefree(p);
} else {
#ifdef DIAGNOSTIC
if (uobj->pgops->pgo_releasepg == NULL)
panic("pagedaemon: no "
"pgo_releasepg function");
#endif
/*
* pgo_releasepg nukes the page and
* gets "nextpg" for us. it returns
* with the page queues locked (when
* given nextpg ptr).
*/
if (!uobj->pgops->pgo_releasepg(p,
&nextpg))
/* uobj died after release */
uobj = NULL;
/*
* lock page queues here so that they're
* always locked at the end of the loop.
*/
uvm_lock_pageq();
}
} else { /* page was not released during I/O */
uvm_lock_pageq();
nextpg = p->pageq.tqe_next;
if (result != VM_PAGER_OK) {
/* pageout was a failure... */
if (result != VM_PAGER_AGAIN)
uvm_pageactivate(p);
pmap_clear_reference(PMAP_PGARG(p));
/* XXXCDC: if (swap_backed) FREE p's
* swap block? */
} else {
/* pageout was a success... */
pmap_clear_reference(PMAP_PGARG(p));
pmap_clear_modify(PMAP_PGARG(p));
p->flags |= PG_CLEAN;
/* XXX: could free page here, but old
* pagedaemon does not */
}
}
/*
* drop object lock (if there is an object left). do
* a safety check of nextpg to make sure it is on the
* inactive queue (it should be since PG_BUSY pages on
* the inactive queue can't be re-queued [note: not
* true for active queue]).
*/
if (anon)
simple_unlock(&anon->an_lock);
else if (uobj)
simple_unlock(&uobj->vmobjlock);
} /* if (p) */ else {
/* if p is null in this loop, make sure it stays null
* in next loop */
nextpg = NULL;
/*
* lock page queues here just so they're always locked
* at the end of the loop.
*/
uvm_lock_pageq();
}
if (nextpg && (nextpg->pqflags & PQ_INACTIVE) == 0) {
printf("pagedaemon: invalid nextpg! reverting to "
"queue head\n");
nextpg = pglst->tqh_first; /* reload! */
}
} /* end of "inactive" 'for' loop */
return (retval);
}
/*
* uvmpd_scan: scan the page queues and attempt to meet our targets.
*
* => called with pageq's locked
*/
void
uvmpd_scan()
{
int s, free, inactive_shortage, swap_shortage, pages_freed;
struct vm_page *p, *nextpg;
struct uvm_object *uobj;
boolean_t got_it;
UVMHIST_FUNC("uvmpd_scan"); UVMHIST_CALLED(pdhist);
uvmexp.pdrevs++; /* counter */
#ifdef __GNUC__
uobj = NULL; /* XXX gcc */
#endif
/*
* get current "free" page count
*/
s = uvm_lock_fpageq();
free = uvmexp.free;
uvm_unlock_fpageq(s);
#ifndef __SWAP_BROKEN
/*
* swap out some processes if we are below our free target.
* we need to unlock the page queues for this.
*/
if (free < uvmexp.freetarg) {
uvmexp.pdswout++;
UVMHIST_LOG(pdhist," free %d < target %d: swapout", free,
uvmexp.freetarg, 0, 0);
uvm_unlock_pageq();
uvm_swapout_threads();
pmap_update(); /* update so we can scan inactive q */
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);
/*
* do loop #1! alternate starting queue between swap and object based
* on the low bit of uvmexp.pdrevs (which we bump by one each call).
*/
got_it = FALSE;
pages_freed = uvmexp.pdfreed;
if ((uvmexp.pdrevs & 1) != 0 && uvmexp.nswapdev != 0)
got_it = uvmpd_scan_inactive(&uvm.page_inactive_swp);
if (!got_it)
got_it = uvmpd_scan_inactive(&uvm.page_inactive_obj);
if (!got_it && (uvmexp.pdrevs & 1) == 0 && uvmexp.nswapdev != 0)
(void) uvmpd_scan_inactive(&uvm.page_inactive_swp);
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 = p->pageq.tqe_next;
if (p->flags & PG_BUSY)
continue; /* quick check before trying to lock */
/*
* lock the page's owner.
*/
/* is page anon owned or ownerless? */
if ((p->pqflags & PQ_ANON) || p->uobject == NULL) {
#ifdef DIAGNOSTIC
if (p->uanon == NULL)
panic("pagedaemon: page with no anon or "
"object detected - loop 2");
#endif
if (!simple_lock_try(&p->uanon->an_lock))
continue;
/* take over the page? */
if ((p->pqflags & PQ_ANON) == 0) {
#ifdef DIAGNOSTIC
if (p->loan_count < 1)
panic("pagedaemon: non-loaned "
"ownerless page detected - loop 2");
#endif
p->loan_count--;
p->pqflags |= PQ_ANON;
}
} else {
if (!simple_lock_try(&p->uobject->vmobjlock))
continue;
}
/*
* skip this page if it's busy.
*/
if ((p->flags & PG_BUSY) != 0) {
if (p->pqflags & PQ_ANON)
simple_unlock(&p->uanon->an_lock);
else
simple_unlock(&p->uobject->vmobjlock);
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) && p->uanon->an_swslot) {
uvm_swap_free(p->uanon->an_swslot, 1);
p->uanon->an_swslot = 0;
p->flags &= ~PG_CLEAN;
swap_shortage--;
}
if (p->pqflags & PQ_AOBJ) {
int slot = uao_set_swslot(p->uobject,
p->offset >> PAGE_SHIFT, 0);
if (slot) {
uvm_swap_free(slot, 1);
p->flags &= ~PG_CLEAN;
swap_shortage--;
}
}
}
/*
* deactivate this page if there's a shortage of
* inactive pages.
*/
if (inactive_shortage > 0) {
pmap_page_protect(PMAP_PGARG(p), VM_PROT_NONE);
/* no need to check wire_count as pg is "active" */
uvm_pagedeactivate(p);
uvmexp.pddeact++;
inactive_shortage--;
}
if (p->pqflags & PQ_ANON)
simple_unlock(&p->uanon->an_lock);
else
simple_unlock(&p->uobject->vmobjlock);
}
}
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