/* $OpenBSD: uvm_pdaemon.c,v 1.66 2014/02/06 16:40:40 tedu Exp $ */ /* $NetBSD: uvm_pdaemon.c,v 1.23 2000/08/20 10:24:14 bjh21 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 #include #include #include #include #include #include #include #include /* * 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(void); boolean_t uvmpd_scan_inactive(struct pglist *); void uvmpd_tune(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(const char *wmsg) { int timo = 0; /* * check for page daemon going to sleep (waiting for itself) */ if (curproc == uvm.pagedaemon_proc) { printf("uvm_wait emergency bufbackoff\n"); if (bufbackoff(NULL, 4) == 0) return; /* * 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 } uvm_lock_fpageq(); wakeup(&uvm.pagedaemon); /* wake the daemon! */ msleep(&uvmexp.free, &uvm.fpageqlock, PVM | PNORELOCK, wmsg, timo); } /* * uvmpd_tune: tune paging parameters * * => called whenever memory is added to (or removed from?) the system * => caller must call with page queues locked */ void uvmpd_tune(void) { uvmexp.freemin = uvmexp.npages / 30; /* between 16k and 512k */ /* XXX: what are these values good for? */ uvmexp.freemin = max(uvmexp.freemin, (16*1024) >> PAGE_SHIFT); #if 0 uvmexp.freemin = min(uvmexp.freemin, (512*1024) >> PAGE_SHIFT); #endif /* 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; } /* * uvm_pageout: the main loop for the pagedaemon */ void uvm_pageout(void *arg) { struct uvm_constraint_range constraint; struct uvm_pmalloc *pma; int work_done; int npages = 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 */ for (;;) { long size; work_done = 0; /* No work done this iteration. */ uvm_lock_fpageq(); if (TAILQ_EMPTY(&uvm.pmr_control.allocs)) { msleep(&uvm.pagedaemon, &uvm.fpageqlock, PVM, "pgdaemon", 0); uvmexp.pdwoke++; } if ((pma = TAILQ_FIRST(&uvm.pmr_control.allocs)) != NULL) { pma->pm_flags |= UVM_PMA_BUSY; constraint = pma->pm_constraint; } else constraint = no_constraint; uvm_unlock_fpageq(); /* * 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; } /* * Reclaim pages from the buffer cache if possible. */ size = 0; if (pma != NULL) size += pma->pm_size >> PAGE_SHIFT; if (uvmexp.free - BUFPAGES_DEFICIT < uvmexp.freetarg) size += uvmexp.freetarg - (uvmexp.free - BUFPAGES_DEFICIT); (void) bufbackoff(&constraint, size * 2); /* * Scan if needed to meet our targets. */ if (pma != NULL || ((uvmexp.free - BUFPAGES_DEFICIT) < uvmexp.freetarg) || ((uvmexp.inactive + BUFPAGES_INACT) < uvmexp.inactarg)) { uvmpd_scan(); work_done = 1; /* XXX we hope... */ } /* * if there's any free memory to be had, * wake up any waiters. */ uvm_lock_fpageq(); if (uvmexp.free > uvmexp.reserve_kernel || uvmexp.paging == 0) { wakeup(&uvmexp.free); } if (pma != NULL) { pma->pm_flags &= ~UVM_PMA_BUSY; if (!work_done) pma->pm_flags |= UVM_PMA_FAIL; if (pma->pm_flags & (UVM_PMA_FAIL | UVM_PMA_FREED)) { pma->pm_flags &= ~UVM_PMA_LINKED; TAILQ_REMOVE(&uvm.pmr_control.allocs, pma, pmq); } wakeup(pma); } uvm_unlock_fpageq(); /* * scan done. unlock page queues (the only lock we are holding) */ uvm_unlock_pageq(); } /*NOTREACHED*/ } /* * uvm_aiodone_daemon: main loop for the aiodone daemon. */ void uvm_aiodone_daemon(void *arg) { int s, free; struct buf *bp, *nbp; uvm.aiodoned_proc = curproc; for (;;) { /* * Check for done aio structures. If we've got structures to * process, do so. Otherwise sleep while avoiding races. */ mtx_enter(&uvm.aiodoned_lock); while ((bp = TAILQ_FIRST(&uvm.aio_done)) == NULL) msleep(&uvm.aiodoned, &uvm.aiodoned_lock, PVM, "aiodoned", 0); /* Take the list for ourselves. */ TAILQ_INIT(&uvm.aio_done); mtx_leave(&uvm.aiodoned_lock); /* * process each i/o that's done. */ free = uvmexp.free; while (bp != NULL) { if (bp->b_flags & B_PDAEMON) { uvmexp.paging -= bp->b_bufsize >> PAGE_SHIFT; } nbp = TAILQ_NEXT(bp, b_freelist); s = splbio(); /* b_iodone must by called at splbio */ (*bp->b_iodone)(bp); splx(s); bp = nbp; } uvm_lock_fpageq(); wakeup(free <= uvmexp.reserve_kernel ? &uvm.pagedaemon : &uvmexp.free); uvm_unlock_fpageq(); } } /* * 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(struct pglist *pglst) { boolean_t retval = FALSE; /* assume we haven't hit target */ int 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; /* * note: we currently keep swap-backed pages on a separate 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 = TAILQ_FIRST(pglst); 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. */ uobj = NULL; anon = NULL; if (p) { /* * update our copy of "free" and see if we've met * our target */ free = uvmexp.free - BUFPAGES_DEFICIT; if (free + uvmexp.paging >= uvmexp.freetarg << 2 || dirtyreacts == UVMPD_NUMDIRTYREACTS) { retval = TRUE; if (swslot == 0) { /* exit now if no swap-i/o pending */ break; } /* set p to null to signal final swap i/o */ p = 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 (unlikely to happen since * inactive pages shouldn't have any valid mappings * and we cleared reference before deactivating). */ if (pmap_is_referenced(p)) { uvm_pageactivate(p); uvmexp.pdreact++; continue; } /* * 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. */ /* is page part of an anon or ownerless ? */ if ((p->pg_flags & PQ_ANON) || p->uobject == NULL) { anon = p->uanon; KASSERT(anon != NULL); /* * if the page is ownerless, claim it in the * name of "anon"! */ if ((p->pg_flags & PQ_ANON) == 0) { KASSERT(p->loan_count > 0); p->loan_count--; atomic_setbits_int(&p->pg_flags, PQ_ANON); /* anon now owns it */ } if (p->pg_flags & PG_BUSY) { uvmexp.pdbusy++; /* someone else owns page, skip it */ continue; } uvmexp.pdanscan++; } else { uobj = p->uobject; KASSERT(uobj != NULL); if (p->pg_flags & PG_BUSY) { uvmexp.pdbusy++; /* someone else owns page, skip it */ continue; } uvmexp.pdobscan++; } /* * we now have the page queues locked. * the page is not busy. if the page is clean we * can free it now and continue. */ if (p->pg_flags & PG_CLEAN) { if (p->pg_flags & PQ_SWAPBACKED) { /* this page now lives only in swap */ uvmexp.swpgonly++; } /* zap all mappings with pmap_page_protect... */ pmap_page_protect(p, VM_PROT_NONE); uvm_pagefree(p); uvmexp.pdfreed++; if (anon) { /* * an anonymous page can only be clean * if it has backing store assigned. */ KASSERT(anon->an_swslot != 0); /* remove from object */ anon->an_page = NULL; } 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) { 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. */ KASSERT(uvmexp.swpgonly <= uvmexp.swpages); if ((p->pg_flags & PQ_SWAPBACKED) && uvmexp.swpgonly == uvmexp.swpages) { dirtyreacts++; uvm_pageactivate(p); 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. */ KASSERT(uvmexp.swpginuse <= uvmexp.swpages); if ((p->pg_flags & PQ_SWAPBACKED) && uvmexp.swpginuse == uvmexp.swpages) { if ((p->pg_flags & PQ_ANON) && p->uanon->an_swslot) { uvm_swap_free(p->uanon->an_swslot, 1); p->uanon->an_swslot = 0; } if (p->pg_flags & 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->pg_flags & PQ_SWAPBACKED) != 0); atomic_setbits_int(&p->pg_flags, PG_BUSY); UVM_PAGE_OWN(p, "scan_inactive"); pmap_page_protect(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) { swnpages = MAXBSIZE >> PAGE_SHIFT; swslot = uvm_swap_alloc(&swnpages, TRUE); if (swslot == 0) { /* no swap? give up! */ atomic_clearbits_int( &p->pg_flags, PG_BUSY); UVM_PAGE_OWN(p, NULL); 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++; } } 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 */ /* 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: page queues * OUT: locked: * !locked: pageqs */ uvmexp.pdpageouts++; result = uvm_pager_put(swap_backed ? NULL : uobj, p, &ppsp, &npages, PGO_ALLPAGES|PGO_PDFREECLUST, start, 0); /* * 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(); uvmexp.pdpending++; if (p) { if (p->pg_flags & PQ_INACTIVE) nextpg = TAILQ_NEXT(p, pageq); else nextpg = TAILQ_FIRST(pglst); } else { nextpg = NULL; } continue; } #ifdef UBC if (result == VM_PAGER_ERROR && curproc == uvm.pagedaemon_proc) { uvm_lock_pageq(); nextpg = TAILQ_NEXT(p, pageq); uvm_pageactivate(p); continue; } #endif /* * 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" */ #ifdef DIAGNOSTIC if (result == VM_PAGER_UNLOCK) panic("pagedaemon: pageout returned " "invalid 'unlock' code"); #endif /* handle PG_WANTED now */ if (p->pg_flags & PG_WANTED) wakeup(p); atomic_clearbits_int(&p->pg_flags, PG_BUSY|PG_WANTED); UVM_PAGE_OWN(p, NULL); /* released during I/O? Can only happen for anons */ if (p->pg_flags & PG_RELEASED) { KASSERT(anon != NULL); /* * remove page so we can get nextpg, * also zero out anon so we don't use * it after the free. */ anon->an_page = NULL; p->uanon = NULL; uvm_anfree(anon); /* kills anon */ pmap_page_protect(p, VM_PROT_NONE); anon = NULL; uvm_lock_pageq(); nextpg = TAILQ_NEXT(p, pageq); /* free released page */ uvm_pagefree(p); } else { /* page was not released during I/O */ uvm_lock_pageq(); nextpg = TAILQ_NEXT(p, pageq); if (result != VM_PAGER_OK) { /* pageout was a failure... */ if (result != VM_PAGER_AGAIN) uvm_pageactivate(p); pmap_clear_reference(p); /* XXXCDC: if (swap_backed) FREE p's * swap block? */ } else { /* pageout was a success... */ pmap_clear_reference(p); pmap_clear_modify(p); atomic_setbits_int(&p->pg_flags, PG_CLEAN); } } /* * 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 (nextpg && (nextpg->pg_flags & PQ_INACTIVE) == 0) { nextpg = TAILQ_FIRST(pglst); /* reload! */ } } else { /* * if p is null in this loop, make sure it stays null * in the next loop. */ nextpg = NULL; /* * lock page queues here just so they're always locked * at the end of the loop. */ uvm_lock_pageq(); } } return (retval); } /* * uvmpd_scan: scan the page queues and attempt to meet our targets. * * => called with pageq's locked */ void uvmpd_scan(void) { int free, inactive_shortage, swap_shortage, pages_freed; struct vm_page *p, *nextpg; struct uvm_object *uobj; boolean_t got_it; uvmexp.pdrevs++; /* counter */ uobj = NULL; /* * get current "free" page count */ free = uvmexp.free - BUFPAGES_DEFICIT; #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++; 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. */ /* * 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; /* XXX - int */ 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 - BUFPAGES_INACT; /* * 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; } for (p = TAILQ_FIRST(&uvm.page_active); p != NULL && (inactive_shortage > 0 || swap_shortage > 0); p = nextpg) { nextpg = TAILQ_NEXT(p, pageq); if (p->pg_flags & PG_BUSY) continue; /* is page anon owned or ownerless? */ if ((p->pg_flags & PQ_ANON) || p->uobject == NULL) { KASSERT(p->uanon != NULL); /* take over the page? */ if ((p->pg_flags & PQ_ANON) == 0) { KASSERT(p->loan_count > 0); p->loan_count--; atomic_setbits_int(&p->pg_flags, PQ_ANON); } } /* * skip this page if it's busy. */ if ((p->pg_flags & PG_BUSY) != 0) { 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->pg_flags & PQ_ANON) && p->uanon->an_swslot) { uvm_swap_free(p->uanon->an_swslot, 1); p->uanon->an_swslot = 0; atomic_clearbits_int(&p->pg_flags, PG_CLEAN); swap_shortage--; } if (p->pg_flags & PQ_AOBJ) { int slot = uao_set_swslot(p->uobject, p->offset >> PAGE_SHIFT, 0); if (slot) { uvm_swap_free(slot, 1); atomic_clearbits_int(&p->pg_flags, PG_CLEAN); swap_shortage--; } } } /* * deactivate this page if there's a shortage of * inactive pages. */ if (inactive_shortage > 0) { pmap_page_protect(p, VM_PROT_NONE); /* no need to check wire_count as pg is "active" */ uvm_pagedeactivate(p); uvmexp.pddeact++; inactive_shortage--; } } }