373 lines
10 KiB
C
373 lines
10 KiB
C
/*
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* Copyright (c) 1991 Regents of the University of California.
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* All rights reserved.
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*
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* This code is derived from software contributed to Berkeley by
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* The Mach Operating System project at Carnegie-Mellon University.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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* 3. All advertising materials mentioning features or use of this software
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* must display the following acknowledgement:
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* This product includes software developed by the University of
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* California, Berkeley and its contributors.
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* 4. Neither the name of the University nor the names of its contributors
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* may be used to endorse or promote products derived from this software
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* without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
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* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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*
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* from: @(#)vm_pageout.c 7.4 (Berkeley) 5/7/91
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* $Id: vm_pageout.c,v 1.12 1994/05/05 20:35:11 mycroft Exp $
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*
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*
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* Copyright (c) 1987, 1990 Carnegie-Mellon University.
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* All rights reserved.
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*
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* Authors: Avadis Tevanian, Jr., Michael Wayne Young
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*
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* Permission to use, copy, modify and distribute this software and
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* its documentation is hereby granted, provided that both the copyright
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* notice and this permission notice appear in all copies of the
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* software, derivative works or modified versions, and any portions
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* thereof, and that both notices appear in supporting documentation.
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*
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* CARNEGIE MELLON ALLOWS FREE USE OF THIS SOFTWARE IN ITS "AS IS"
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* CONDITION. CARNEGIE MELLON DISCLAIMS ANY LIABILITY OF ANY KIND
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* FOR ANY DAMAGES WHATSOEVER RESULTING FROM THE USE OF THIS SOFTWARE.
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*
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* Carnegie Mellon requests users of this software to return to
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*
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* Software Distribution Coordinator or Software.Distribution@CS.CMU.EDU
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* School of Computer Science
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* Carnegie Mellon University
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* Pittsburgh PA 15213-3890
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*
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* any improvements or extensions that they make and grant Carnegie the
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* rights to redistribute these changes.
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*/
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/*
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* The proverbial page-out daemon.
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*/
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#include <sys/param.h>
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#include <sys/vmmeter.h>
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#include <vm/vm.h>
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#include <vm/vm_page.h>
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#include <vm/vm_pageout.h>
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#include <machine/cpu.h>
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int vm_pages_needed; /* Event on which pageout daemon sleeps */
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int vm_pageout_free_min = 0; /* Stop pageout to wait for pagers at this free level */
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int vm_page_free_min_sanity = 40;
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/*
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* vm_pageout_scan does the dirty work for the pageout daemon.
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*/
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void
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vm_pageout_scan()
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{
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register vm_page_t m, next;
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register int page_shortage;
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register int s;
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register int pages_freed;
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int free;
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vm_object_t object;
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/*
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* Only continue when we want more pages to be "free"
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*/
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s = splimp();
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simple_lock(&vm_page_queue_free_lock);
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free = cnt.v_free_count;
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simple_unlock(&vm_page_queue_free_lock);
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splx(s);
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if (free < cnt.v_free_target) {
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#ifdef OMIT
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swapout_threads();
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#endif /* OMIT*/
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/*
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* Be sure the pmap system is updated so
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* we can scan the inactive queue.
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*/
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pmap_update();
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}
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/*
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* Acquire the resident page system lock,
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* as we may be changing what's resident quite a bit.
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*/
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vm_page_lock_queues();
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/*
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* Start scanning the inactive queue for pages we can free.
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* We keep scanning until we have enough free pages or
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* we have scanned through the entire queue. If we
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* encounter dirty pages, we start cleaning them.
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*/
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pages_freed = 0;
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for (m = vm_page_queue_inactive.tqh_first; m != NULL; m = next) {
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s = splimp();
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simple_lock(&vm_page_queue_free_lock);
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free = cnt.v_free_count;
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simple_unlock(&vm_page_queue_free_lock);
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splx(s);
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if (free >= cnt.v_free_target)
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break;
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cnt.v_scan++;
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next = m->pageq.tqe_next;
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/*
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* If the page has been referenced, move it back to the
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* active queue.
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*/
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if (pmap_is_referenced(VM_PAGE_TO_PHYS(m))) {
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vm_page_activate(m);
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cnt.v_reactivated++;
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continue;
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}
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/*
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* If the page is clean, free it up.
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*/
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if (m->flags & PG_CLEAN) {
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object = m->object;
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if (vm_object_lock_try(object)) {
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pmap_page_protect(VM_PAGE_TO_PHYS(m),
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VM_PROT_NONE);
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vm_page_free(m);
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pages_freed++;
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cnt.v_dfree++;
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vm_object_unlock(object);
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}
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continue;
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}
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/*
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* If the page is dirty but already being washed, skip it.
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*/
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if ((m->flags & PG_LAUNDRY) == 0)
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continue;
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/*
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* Otherwise the page is dirty and still in the laundry,
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* so we start the cleaning operation and remove it from
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* the laundry.
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*/
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object = m->object;
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if (!vm_object_lock_try(object))
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continue;
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cnt.v_pageouts++;
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vm_pageout_page(m, object);
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thread_wakeup((int) object);
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vm_object_unlock(object);
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/*
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* Former next page may no longer even be on the inactive
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* queue (due to potential blocking in the pager with the
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* queues unlocked). If it isn't, we just start over.
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*/
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if (next && (next->flags & PG_INACTIVE) == 0)
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next = vm_page_queue_inactive.tqh_first;
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}
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/*
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* Compute the page shortage. If we are still very low on memory
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* be sure that we will move a minimal amount of pages from active
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* to inactive.
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*/
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page_shortage = cnt.v_inactive_target - cnt.v_inactive_count;
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if (page_shortage <= 0 && pages_freed == 0)
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page_shortage = 1;
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while (page_shortage > 0) {
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/*
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* Move some more pages from active to inactive.
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*/
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if ((m = vm_page_queue_active.tqh_first) == NULL)
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break;
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vm_page_deactivate(m);
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page_shortage--;
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}
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vm_page_unlock_queues();
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}
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/*
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* Called with object and page queues locked.
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* If reactivate is TRUE, a pager error causes the page to be
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* put back on the active queue, ow it is left on the inactive queue.
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*/
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void
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vm_pageout_page(m, object)
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vm_page_t m;
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vm_object_t object;
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{
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vm_pager_t pager;
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int pageout_status;
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/*
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* We set the busy bit to cause potential page faults on
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* this page to block.
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*
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* We also set pageout-in-progress to keep the object from
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* disappearing during pageout. This guarantees that the
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* page won't move from the inactive queue. (However, any
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* other page on the inactive queue may move!)
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*/
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pmap_page_protect(VM_PAGE_TO_PHYS(m), VM_PROT_NONE);
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m->flags |= PG_BUSY;
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/*
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* Try to collapse the object before making a pager for it.
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* We must unlock the page queues first.
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*/
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vm_page_unlock_queues();
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if (object->pager == NULL)
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vm_object_collapse(object);
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object->paging_in_progress++;
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vm_object_unlock(object);
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/*
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* Do a wakeup here in case the following operations block.
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*/
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thread_wakeup((int) &cnt.v_free_count);
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/*
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* If there is no pager for the page, use the default pager.
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* If there is no place to put the page at the moment,
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* leave it in the laundry and hope that there will be
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* paging space later.
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*/
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if ((pager = object->pager) == NULL) {
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pager = vm_pager_allocate(PG_DFLT, (caddr_t)0, object->size,
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VM_PROT_ALL, (vm_offset_t)0);
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if (pager != NULL)
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vm_object_setpager(object, pager, 0, FALSE);
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}
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pageout_status = pager ? vm_pager_put(pager, m, FALSE) : VM_PAGER_FAIL;
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vm_object_lock(object);
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vm_page_lock_queues();
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switch (pageout_status) {
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case VM_PAGER_OK:
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case VM_PAGER_PEND:
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cnt.v_pgpgout++;
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m->flags &= ~PG_LAUNDRY;
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break;
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case VM_PAGER_BAD:
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/*
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* Page outside of range of object. Right now we
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* essentially lose the changes by pretending it
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* worked.
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*
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* XXX dubious, what should we do?
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*/
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m->flags &= ~PG_LAUNDRY;
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m->flags |= PG_CLEAN;
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pmap_clear_modify(VM_PAGE_TO_PHYS(m));
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break;
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case VM_PAGER_FAIL:
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/*
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* If page couldn't be paged out, then reactivate
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* the page so it doesn't clog the inactive list.
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* (We will try paging out it again later).
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*/
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vm_page_activate(m);
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cnt.v_reactivated++;
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break;
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}
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pmap_clear_reference(VM_PAGE_TO_PHYS(m));
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/*
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* If the operation is still going, leave the page busy
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* to block all other accesses. Also, leave the paging
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* in progress indicator set so that we don't attempt an
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* object collapse.
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*/
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if (pageout_status != VM_PAGER_PEND) {
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m->flags &= ~PG_BUSY;
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PAGE_WAKEUP(m);
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object->paging_in_progress--;
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}
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}
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/*
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* vm_pageout is the high level pageout daemon.
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*/
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void
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vm_pageout()
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{
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(void) spl0();
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/*
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* Initialize some paging parameters.
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*/
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if (cnt.v_free_min == 0) {
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cnt.v_free_min = cnt.v_free_count / 20;
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if (cnt.v_free_min < 3)
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cnt.v_free_min = 3;
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if (cnt.v_free_min > vm_page_free_min_sanity)
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cnt.v_free_min = vm_page_free_min_sanity;
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}
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if (cnt.v_free_target == 0)
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cnt.v_free_target = (cnt.v_free_min * 4) / 3;
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if (cnt.v_inactive_target == 0)
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cnt.v_inactive_target = cnt.v_free_min * 2;
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if (cnt.v_free_target <= cnt.v_free_min)
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cnt.v_free_target = cnt.v_free_min + 1;
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if (cnt.v_inactive_target <= cnt.v_free_target)
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cnt.v_inactive_target = cnt.v_free_target + 1;
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/*
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* The pageout daemon is never done, so loop
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* forever.
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*/
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simple_lock(&vm_pages_needed_lock);
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while (TRUE) {
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thread_sleep((int) &vm_pages_needed, &vm_pages_needed_lock);
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cnt.v_scan++;
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vm_pageout_scan();
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vm_pager_sync();
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simple_lock(&vm_pages_needed_lock);
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thread_wakeup((int) &cnt.v_free_count);
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}
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}
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