FreeBSD-5.3/sys/vm/vm_pageout.c
/*
* Copyright (c) 1991 Regents of the University of California.
* All rights reserved.
* Copyright (c) 1994 John S. Dyson
* All rights reserved.
* Copyright (c) 1994 David Greenman
* 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 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.
*
* from: @(#)vm_pageout.c 7.4 (Berkeley) 5/7/91
*
*
* Copyright (c) 1987, 1990 Carnegie-Mellon University.
* All rights reserved.
*
* Authors: Avadis Tevanian, Jr., Michael Wayne Young
*
* 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.
*/
/*
* The proverbial page-out daemon.
*/
#include <sys/cdefs.h>
__FBSDID("$FreeBSD: src/sys/vm/vm_pageout.c,v 1.261 2004/07/18 04:38:11 alc Exp $");
#include "opt_vm.h"
#include <sys/param.h>
#include <sys/systm.h>
#include <sys/kernel.h>
#include <sys/eventhandler.h>
#include <sys/lock.h>
#include <sys/mutex.h>
#include <sys/proc.h>
#include <sys/kthread.h>
#include <sys/ktr.h>
#include <sys/resourcevar.h>
#include <sys/sched.h>
#include <sys/signalvar.h>
#include <sys/vnode.h>
#include <sys/vmmeter.h>
#include <sys/sx.h>
#include <sys/sysctl.h>
#include <vm/vm.h>
#include <vm/vm_param.h>
#include <vm/vm_object.h>
#include <vm/vm_page.h>
#include <vm/vm_map.h>
#include <vm/vm_pageout.h>
#include <vm/vm_pager.h>
#include <vm/swap_pager.h>
#include <vm/vm_extern.h>
#include <vm/uma.h>
#include <machine/mutex.h>
/*
* System initialization
*/
/* the kernel process "vm_pageout"*/
static void vm_pageout(void);
static int vm_pageout_clean(vm_page_t);
static void vm_pageout_pmap_collect(void);
static void vm_pageout_scan(int pass);
struct proc *pageproc;
static struct kproc_desc page_kp = {
"pagedaemon",
vm_pageout,
&pageproc
};
SYSINIT(pagedaemon, SI_SUB_KTHREAD_PAGE, SI_ORDER_FIRST, kproc_start, &page_kp)
#if !defined(NO_SWAPPING)
/* the kernel process "vm_daemon"*/
static void vm_daemon(void);
static struct proc *vmproc;
static struct kproc_desc vm_kp = {
"vmdaemon",
vm_daemon,
&vmproc
};
SYSINIT(vmdaemon, SI_SUB_KTHREAD_VM, SI_ORDER_FIRST, kproc_start, &vm_kp)
#endif
int vm_pages_needed; /* Event on which pageout daemon sleeps */
int vm_pageout_deficit; /* Estimated number of pages deficit */
int vm_pageout_pages_needed; /* flag saying that the pageout daemon needs pages */
#if !defined(NO_SWAPPING)
static int vm_pageout_req_swapout; /* XXX */
static int vm_daemon_needed;
#endif
static int vm_max_launder = 32;
static int vm_pageout_stats_max=0, vm_pageout_stats_interval = 0;
static int vm_pageout_full_stats_interval = 0;
static int vm_pageout_algorithm=0;
static int defer_swap_pageouts=0;
static int disable_swap_pageouts=0;
#if defined(NO_SWAPPING)
static int vm_swap_enabled=0;
static int vm_swap_idle_enabled=0;
#else
static int vm_swap_enabled=1;
static int vm_swap_idle_enabled=0;
#endif
SYSCTL_INT(_vm, VM_PAGEOUT_ALGORITHM, pageout_algorithm,
CTLFLAG_RW, &vm_pageout_algorithm, 0, "LRU page mgmt");
SYSCTL_INT(_vm, OID_AUTO, max_launder,
CTLFLAG_RW, &vm_max_launder, 0, "Limit dirty flushes in pageout");
SYSCTL_INT(_vm, OID_AUTO, pageout_stats_max,
CTLFLAG_RW, &vm_pageout_stats_max, 0, "Max pageout stats scan length");
SYSCTL_INT(_vm, OID_AUTO, pageout_full_stats_interval,
CTLFLAG_RW, &vm_pageout_full_stats_interval, 0, "Interval for full stats scan");
SYSCTL_INT(_vm, OID_AUTO, pageout_stats_interval,
CTLFLAG_RW, &vm_pageout_stats_interval, 0, "Interval for partial stats scan");
#if defined(NO_SWAPPING)
SYSCTL_INT(_vm, VM_SWAPPING_ENABLED, swap_enabled,
CTLFLAG_RD, &vm_swap_enabled, 0, "");
SYSCTL_INT(_vm, OID_AUTO, swap_idle_enabled,
CTLFLAG_RD, &vm_swap_idle_enabled, 0, "");
#else
SYSCTL_INT(_vm, VM_SWAPPING_ENABLED, swap_enabled,
CTLFLAG_RW, &vm_swap_enabled, 0, "Enable entire process swapout");
SYSCTL_INT(_vm, OID_AUTO, swap_idle_enabled,
CTLFLAG_RW, &vm_swap_idle_enabled, 0, "Allow swapout on idle criteria");
#endif
SYSCTL_INT(_vm, OID_AUTO, defer_swapspace_pageouts,
CTLFLAG_RW, &defer_swap_pageouts, 0, "Give preference to dirty pages in mem");
SYSCTL_INT(_vm, OID_AUTO, disable_swapspace_pageouts,
CTLFLAG_RW, &disable_swap_pageouts, 0, "Disallow swapout of dirty pages");
static int pageout_lock_miss;
SYSCTL_INT(_vm, OID_AUTO, pageout_lock_miss,
CTLFLAG_RD, &pageout_lock_miss, 0, "vget() lock misses during pageout");
#define VM_PAGEOUT_PAGE_COUNT 16
int vm_pageout_page_count = VM_PAGEOUT_PAGE_COUNT;
int vm_page_max_wired; /* XXX max # of wired pages system-wide */
#if !defined(NO_SWAPPING)
static void vm_pageout_map_deactivate_pages(vm_map_t, long);
static void vm_pageout_object_deactivate_pages(pmap_t, vm_object_t, long);
static void vm_req_vmdaemon(void);
#endif
static void vm_pageout_page_stats(void);
/*
* vm_pageout_clean:
*
* Clean the page and remove it from the laundry.
*
* We set the busy bit to cause potential page faults on this page to
* block. Note the careful timing, however, the busy bit isn't set till
* late and we cannot do anything that will mess with the page.
*/
static int
vm_pageout_clean(m)
vm_page_t m;
{
vm_object_t object;
vm_page_t mc[2*vm_pageout_page_count];
int pageout_count;
int ib, is, page_base;
vm_pindex_t pindex = m->pindex;
mtx_assert(&vm_page_queue_mtx, MA_OWNED);
VM_OBJECT_LOCK_ASSERT(m->object, MA_OWNED);
/*
* It doesn't cost us anything to pageout OBJT_DEFAULT or OBJT_SWAP
* with the new swapper, but we could have serious problems paging
* out other object types if there is insufficient memory.
*
* Unfortunately, checking free memory here is far too late, so the
* check has been moved up a procedural level.
*/
/*
* Don't mess with the page if it's busy, held, or special
*/
if ((m->hold_count != 0) ||
((m->busy != 0) || (m->flags & (PG_BUSY|PG_UNMANAGED)))) {
return 0;
}
mc[vm_pageout_page_count] = m;
pageout_count = 1;
page_base = vm_pageout_page_count;
ib = 1;
is = 1;
/*
* Scan object for clusterable pages.
*
* We can cluster ONLY if: ->> the page is NOT
* clean, wired, busy, held, or mapped into a
* buffer, and one of the following:
* 1) The page is inactive, or a seldom used
* active page.
* -or-
* 2) we force the issue.
*
* During heavy mmap/modification loads the pageout
* daemon can really fragment the underlying file
* due to flushing pages out of order and not trying
* align the clusters (which leave sporatic out-of-order
* holes). To solve this problem we do the reverse scan
* first and attempt to align our cluster, then do a
* forward scan if room remains.
*/
object = m->object;
more:
while (ib && pageout_count < vm_pageout_page_count) {
vm_page_t p;
if (ib > pindex) {
ib = 0;
break;
}
if ((p = vm_page_lookup(object, pindex - ib)) == NULL) {
ib = 0;
break;
}
if (((p->queue - p->pc) == PQ_CACHE) ||
(p->flags & (PG_BUSY|PG_UNMANAGED)) || p->busy) {
ib = 0;
break;
}
vm_page_test_dirty(p);
if ((p->dirty & p->valid) == 0 ||
p->queue != PQ_INACTIVE ||
p->wire_count != 0 || /* may be held by buf cache */
p->hold_count != 0) { /* may be undergoing I/O */
ib = 0;
break;
}
mc[--page_base] = p;
++pageout_count;
++ib;
/*
* alignment boundry, stop here and switch directions. Do
* not clear ib.
*/
if ((pindex - (ib - 1)) % vm_pageout_page_count == 0)
break;
}
while (pageout_count < vm_pageout_page_count &&
pindex + is < object->size) {
vm_page_t p;
if ((p = vm_page_lookup(object, pindex + is)) == NULL)
break;
if (((p->queue - p->pc) == PQ_CACHE) ||
(p->flags & (PG_BUSY|PG_UNMANAGED)) || p->busy) {
break;
}
vm_page_test_dirty(p);
if ((p->dirty & p->valid) == 0 ||
p->queue != PQ_INACTIVE ||
p->wire_count != 0 || /* may be held by buf cache */
p->hold_count != 0) { /* may be undergoing I/O */
break;
}
mc[page_base + pageout_count] = p;
++pageout_count;
++is;
}
/*
* If we exhausted our forward scan, continue with the reverse scan
* when possible, even past a page boundry. This catches boundry
* conditions.
*/
if (ib && pageout_count < vm_pageout_page_count)
goto more;
/*
* we allow reads during pageouts...
*/
return (vm_pageout_flush(&mc[page_base], pageout_count, 0));
}
/*
* vm_pageout_flush() - launder the given pages
*
* The given pages are laundered. Note that we setup for the start of
* I/O ( i.e. busy the page ), mark it read-only, and bump the object
* reference count all in here rather then in the parent. If we want
* the parent to do more sophisticated things we may have to change
* the ordering.
*/
int
vm_pageout_flush(vm_page_t *mc, int count, int flags)
{
vm_object_t object = mc[0]->object;
int pageout_status[count];
int numpagedout = 0;
int i;
mtx_assert(&vm_page_queue_mtx, MA_OWNED);
VM_OBJECT_LOCK_ASSERT(object, MA_OWNED);
/*
* Initiate I/O. Bump the vm_page_t->busy counter and
* mark the pages read-only.
*
* We do not have to fixup the clean/dirty bits here... we can
* allow the pager to do it after the I/O completes.
*
* NOTE! mc[i]->dirty may be partial or fragmented due to an
* edge case with file fragments.
*/
for (i = 0; i < count; i++) {
KASSERT(mc[i]->valid == VM_PAGE_BITS_ALL,
("vm_pageout_flush: partially invalid page %p index %d/%d",
mc[i], i, count));
vm_page_io_start(mc[i]);
pmap_page_protect(mc[i], VM_PROT_READ);
}
vm_page_unlock_queues();
vm_object_pip_add(object, count);
vm_pager_put_pages(object, mc, count,
(flags | ((object == kernel_object) ? VM_PAGER_PUT_SYNC : 0)),
pageout_status);
vm_page_lock_queues();
for (i = 0; i < count; i++) {
vm_page_t mt = mc[i];
KASSERT((mt->flags & PG_WRITEABLE) == 0,
("vm_pageout_flush: page %p is not write protected", mt));
switch (pageout_status[i]) {
case VM_PAGER_OK:
case VM_PAGER_PEND:
numpagedout++;
break;
case VM_PAGER_BAD:
/*
* Page outside of range of object. Right now we
* essentially lose the changes by pretending it
* worked.
*/
pmap_clear_modify(mt);
vm_page_undirty(mt);
break;
case VM_PAGER_ERROR:
case VM_PAGER_FAIL:
/*
* If page couldn't be paged out, then reactivate the
* page so it doesn't clog the inactive list. (We
* will try paging out it again later).
*/
vm_page_activate(mt);
break;
case VM_PAGER_AGAIN:
break;
}
/*
* If the operation is still going, leave the page busy to
* block all other accesses. Also, leave the paging in
* progress indicator set so that we don't attempt an object
* collapse.
*/
if (pageout_status[i] != VM_PAGER_PEND) {
vm_object_pip_wakeup(object);
vm_page_io_finish(mt);
if (vm_page_count_severe())
vm_page_try_to_cache(mt);
}
}
return numpagedout;
}
#if !defined(NO_SWAPPING)
/*
* vm_pageout_object_deactivate_pages
*
* deactivate enough pages to satisfy the inactive target
* requirements or if vm_page_proc_limit is set, then
* deactivate all of the pages in the object and its
* backing_objects.
*
* The object and map must be locked.
*/
static void
vm_pageout_object_deactivate_pages(pmap, first_object, desired)
pmap_t pmap;
vm_object_t first_object;
long desired;
{
vm_object_t backing_object, object;
vm_page_t p, next;
int actcount, rcount, remove_mode;
VM_OBJECT_LOCK_ASSERT(first_object, MA_OWNED);
if (first_object->type == OBJT_DEVICE || first_object->type == OBJT_PHYS)
return;
for (object = first_object;; object = backing_object) {
if (pmap_resident_count(pmap) <= desired)
goto unlock_return;
if (object->paging_in_progress)
goto unlock_return;
remove_mode = 0;
if (object->shadow_count > 1)
remove_mode = 1;
/*
* scan the objects entire memory queue
*/
rcount = object->resident_page_count;
p = TAILQ_FIRST(&object->memq);
vm_page_lock_queues();
while (p && (rcount-- > 0)) {
if (pmap_resident_count(pmap) <= desired) {
vm_page_unlock_queues();
goto unlock_return;
}
next = TAILQ_NEXT(p, listq);
cnt.v_pdpages++;
if (p->wire_count != 0 ||
p->hold_count != 0 ||
p->busy != 0 ||
(p->flags & (PG_BUSY|PG_UNMANAGED)) ||
!pmap_page_exists_quick(pmap, p)) {
p = next;
continue;
}
actcount = pmap_ts_referenced(p);
if (actcount) {
vm_page_flag_set(p, PG_REFERENCED);
} else if (p->flags & PG_REFERENCED) {
actcount = 1;
}
if ((p->queue != PQ_ACTIVE) &&
(p->flags & PG_REFERENCED)) {
vm_page_activate(p);
p->act_count += actcount;
vm_page_flag_clear(p, PG_REFERENCED);
} else if (p->queue == PQ_ACTIVE) {
if ((p->flags & PG_REFERENCED) == 0) {
p->act_count -= min(p->act_count, ACT_DECLINE);
if (!remove_mode && (vm_pageout_algorithm || (p->act_count == 0))) {
pmap_remove_all(p);
vm_page_deactivate(p);
} else {
vm_pageq_requeue(p);
}
} else {
vm_page_activate(p);
vm_page_flag_clear(p, PG_REFERENCED);
if (p->act_count < (ACT_MAX - ACT_ADVANCE))
p->act_count += ACT_ADVANCE;
vm_pageq_requeue(p);
}
} else if (p->queue == PQ_INACTIVE) {
pmap_remove_all(p);
}
p = next;
}
vm_page_unlock_queues();
if ((backing_object = object->backing_object) == NULL)
goto unlock_return;
VM_OBJECT_LOCK(backing_object);
if (object != first_object)
VM_OBJECT_UNLOCK(object);
}
unlock_return:
if (object != first_object)
VM_OBJECT_UNLOCK(object);
}
/*
* deactivate some number of pages in a map, try to do it fairly, but
* that is really hard to do.
*/
static void
vm_pageout_map_deactivate_pages(map, desired)
vm_map_t map;
long desired;
{
vm_map_entry_t tmpe;
vm_object_t obj, bigobj;
int nothingwired;
if (!vm_map_trylock(map))
return;
bigobj = NULL;
nothingwired = TRUE;
/*
* first, search out the biggest object, and try to free pages from
* that.
*/
tmpe = map->header.next;
while (tmpe != &map->header) {
if ((tmpe->eflags & MAP_ENTRY_IS_SUB_MAP) == 0) {
obj = tmpe->object.vm_object;
if (obj != NULL && VM_OBJECT_TRYLOCK(obj)) {
if (obj->shadow_count <= 1 &&
(bigobj == NULL ||
bigobj->resident_page_count < obj->resident_page_count)) {
if (bigobj != NULL)
VM_OBJECT_UNLOCK(bigobj);
bigobj = obj;
} else
VM_OBJECT_UNLOCK(obj);
}
}
if (tmpe->wired_count > 0)
nothingwired = FALSE;
tmpe = tmpe->next;
}
if (bigobj != NULL) {
vm_pageout_object_deactivate_pages(map->pmap, bigobj, desired);
VM_OBJECT_UNLOCK(bigobj);
}
/*
* Next, hunt around for other pages to deactivate. We actually
* do this search sort of wrong -- .text first is not the best idea.
*/
tmpe = map->header.next;
while (tmpe != &map->header) {
if (pmap_resident_count(vm_map_pmap(map)) <= desired)
break;
if ((tmpe->eflags & MAP_ENTRY_IS_SUB_MAP) == 0) {
obj = tmpe->object.vm_object;
if (obj != NULL) {
VM_OBJECT_LOCK(obj);
vm_pageout_object_deactivate_pages(map->pmap, obj, desired);
VM_OBJECT_UNLOCK(obj);
}
}
tmpe = tmpe->next;
}
/*
* Remove all mappings if a process is swapped out, this will free page
* table pages.
*/
if (desired == 0 && nothingwired) {
pmap_remove(vm_map_pmap(map), vm_map_min(map),
vm_map_max(map));
}
vm_map_unlock(map);
}
#endif /* !defined(NO_SWAPPING) */
/*
* This routine is very drastic, but can save the system
* in a pinch.
*/
static void
vm_pageout_pmap_collect(void)
{
int i;
vm_page_t m;
static int warningdone;
if (pmap_pagedaemon_waken == 0)
return;
if (warningdone < 5) {
printf("collecting pv entries -- suggest increasing PMAP_SHPGPERPROC\n");
warningdone++;
}
vm_page_lock_queues();
for (i = 0; i < vm_page_array_size; i++) {
m = &vm_page_array[i];
if (m->wire_count || m->hold_count || m->busy ||
(m->flags & (PG_BUSY | PG_UNMANAGED)))
continue;
pmap_remove_all(m);
}
vm_page_unlock_queues();
pmap_pagedaemon_waken = 0;
}
/*
* vm_pageout_scan does the dirty work for the pageout daemon.
*/
static void
vm_pageout_scan(int pass)
{
vm_page_t m, next;
struct vm_page marker;
int page_shortage, maxscan, pcount;
int addl_page_shortage, addl_page_shortage_init;
struct proc *p, *bigproc;
struct thread *td;
vm_offset_t size, bigsize;
vm_object_t object;
int actcount;
int vnodes_skipped = 0;
int maxlaunder;
mtx_lock(&Giant);
/*
* Decrease registered cache sizes.
*/
EVENTHANDLER_INVOKE(vm_lowmem, 0);
/*
* We do this explicitly after the caches have been drained above.
*/
uma_reclaim();
/*
* Do whatever cleanup that the pmap code can.
*/
vm_pageout_pmap_collect();
addl_page_shortage_init = atomic_readandclear_int(&vm_pageout_deficit);
/*
* Calculate the number of pages we want to either free or move
* to the cache.
*/
page_shortage = vm_paging_target() + addl_page_shortage_init;
/*
* Initialize our marker
*/
bzero(&marker, sizeof(marker));
marker.flags = PG_BUSY | PG_FICTITIOUS | PG_MARKER;
marker.queue = PQ_INACTIVE;
marker.wire_count = 1;
/*
* Start scanning the inactive queue for pages we can move to the
* cache or free. The scan will stop when the target is reached or
* we have scanned the entire inactive queue. Note that m->act_count
* is not used to form decisions for the inactive queue, only for the
* active queue.
*
* maxlaunder limits the number of dirty pages we flush per scan.
* For most systems a smaller value (16 or 32) is more robust under
* extreme memory and disk pressure because any unnecessary writes
* to disk can result in extreme performance degredation. However,
* systems with excessive dirty pages (especially when MAP_NOSYNC is
* used) will die horribly with limited laundering. If the pageout
* daemon cannot clean enough pages in the first pass, we let it go
* all out in succeeding passes.
*/
if ((maxlaunder = vm_max_launder) <= 1)
maxlaunder = 1;
if (pass)
maxlaunder = 10000;
vm_page_lock_queues();
rescan0:
addl_page_shortage = addl_page_shortage_init;
maxscan = cnt.v_inactive_count;
for (m = TAILQ_FIRST(&vm_page_queues[PQ_INACTIVE].pl);
m != NULL && maxscan-- > 0 && page_shortage > 0;
m = next) {
cnt.v_pdpages++;
if (m->queue != PQ_INACTIVE) {
goto rescan0;
}
next = TAILQ_NEXT(m, pageq);
/*
* skip marker pages
*/
if (m->flags & PG_MARKER)
continue;
/*
* A held page may be undergoing I/O, so skip it.
*/
if (m->hold_count) {
vm_pageq_requeue(m);
addl_page_shortage++;
continue;
}
/*
* Don't mess with busy pages, keep in the front of the
* queue, most likely are being paged out.
*/
if (m->busy || (m->flags & PG_BUSY)) {
addl_page_shortage++;
continue;
}
/*
* If the object is not being used, we ignore previous
* references.
*/
if (m->object->ref_count == 0) {
vm_page_flag_clear(m, PG_REFERENCED);
pmap_clear_reference(m);
/*
* Otherwise, if the page has been referenced while in the
* inactive queue, we bump the "activation count" upwards,
* making it less likely that the page will be added back to
* the inactive queue prematurely again. Here we check the
* page tables (or emulated bits, if any), given the upper
* level VM system not knowing anything about existing
* references.
*/
} else if (((m->flags & PG_REFERENCED) == 0) &&
(actcount = pmap_ts_referenced(m))) {
vm_page_activate(m);
m->act_count += (actcount + ACT_ADVANCE);
continue;
}
/*
* If the upper level VM system knows about any page
* references, we activate the page. We also set the
* "activation count" higher than normal so that we will less
* likely place pages back onto the inactive queue again.
*/
if ((m->flags & PG_REFERENCED) != 0) {
vm_page_flag_clear(m, PG_REFERENCED);
actcount = pmap_ts_referenced(m);
vm_page_activate(m);
m->act_count += (actcount + ACT_ADVANCE + 1);
continue;
}
/*
* If the upper level VM system doesn't know anything about
* the page being dirty, we have to check for it again. As
* far as the VM code knows, any partially dirty pages are
* fully dirty.
*/
if (m->dirty == 0 && !pmap_is_modified(m)) {
/*
* Avoid a race condition: Unless write access is
* removed from the page, another processor could
* modify it before all access is removed by the call
* to vm_page_cache() below. If vm_page_cache() finds
* that the page has been modified when it removes all
* access, it panics because it cannot cache dirty
* pages. In principle, we could eliminate just write
* access here rather than all access. In the expected
* case, when there are no last instant modifications
* to the page, removing all access will be cheaper
* overall.
*/
if ((m->flags & PG_WRITEABLE) != 0)
pmap_remove_all(m);
} else {
vm_page_dirty(m);
}
object = m->object;
if (!VM_OBJECT_TRYLOCK(object))
continue;
if (m->valid == 0) {
/*
* Invalid pages can be easily freed
*/
vm_page_busy(m);
pmap_remove_all(m);
vm_page_free(m);
cnt.v_dfree++;
--page_shortage;
} else if (m->dirty == 0) {
/*
* Clean pages can be placed onto the cache queue.
* This effectively frees them.
*/
vm_page_cache(m);
--page_shortage;
} else if ((m->flags & PG_WINATCFLS) == 0 && pass == 0) {
/*
* Dirty pages need to be paged out, but flushing
* a page is extremely expensive verses freeing
* a clean page. Rather then artificially limiting
* the number of pages we can flush, we instead give
* dirty pages extra priority on the inactive queue
* by forcing them to be cycled through the queue
* twice before being flushed, after which the
* (now clean) page will cycle through once more
* before being freed. This significantly extends
* the thrash point for a heavily loaded machine.
*/
vm_page_flag_set(m, PG_WINATCFLS);
vm_pageq_requeue(m);
} else if (maxlaunder > 0) {
/*
* We always want to try to flush some dirty pages if
* we encounter them, to keep the system stable.
* Normally this number is small, but under extreme
* pressure where there are insufficient clean pages
* on the inactive queue, we may have to go all out.
*/
int swap_pageouts_ok;
struct vnode *vp = NULL;
struct mount *mp;
if ((object->type != OBJT_SWAP) && (object->type != OBJT_DEFAULT)) {
swap_pageouts_ok = 1;
} else {
swap_pageouts_ok = !(defer_swap_pageouts || disable_swap_pageouts);
swap_pageouts_ok |= (!disable_swap_pageouts && defer_swap_pageouts &&
vm_page_count_min());
}
/*
* We don't bother paging objects that are "dead".
* Those objects are in a "rundown" state.
*/
if (!swap_pageouts_ok || (object->flags & OBJ_DEAD)) {
VM_OBJECT_UNLOCK(object);
vm_pageq_requeue(m);
continue;
}
/*
* The object is already known NOT to be dead. It
* is possible for the vget() to block the whole
* pageout daemon, but the new low-memory handling
* code should prevent it.
*
* The previous code skipped locked vnodes and, worse,
* reordered pages in the queue. This results in
* completely non-deterministic operation and, on a
* busy system, can lead to extremely non-optimal
* pageouts. For example, it can cause clean pages
* to be freed and dirty pages to be moved to the end
* of the queue. Since dirty pages are also moved to
* the end of the queue once-cleaned, this gives
* way too large a weighting to defering the freeing
* of dirty pages.
*
* We can't wait forever for the vnode lock, we might
* deadlock due to a vn_read() getting stuck in
* vm_wait while holding this vnode. We skip the
* vnode if we can't get it in a reasonable amount
* of time.
*/
if (object->type == OBJT_VNODE) {
vp = object->handle;
mp = NULL;
if (vp->v_type == VREG)
vn_start_write(vp, &mp, V_NOWAIT);
vm_page_unlock_queues();
VI_LOCK(vp);
VM_OBJECT_UNLOCK(object);
if (vget(vp, LK_EXCLUSIVE | LK_INTERLOCK |
LK_TIMELOCK, curthread)) {
VM_OBJECT_LOCK(object);
vm_page_lock_queues();
++pageout_lock_miss;
vn_finished_write(mp);
if (object->flags & OBJ_MIGHTBEDIRTY)
vnodes_skipped++;
VM_OBJECT_UNLOCK(object);
continue;
}
VM_OBJECT_LOCK(object);
vm_page_lock_queues();
/*
* The page might have been moved to another
* queue during potential blocking in vget()
* above. The page might have been freed and
* reused for another vnode. The object might
* have been reused for another vnode.
*/
if (m->queue != PQ_INACTIVE ||
m->object != object ||
object->handle != vp) {
if (object->flags & OBJ_MIGHTBEDIRTY)
vnodes_skipped++;
goto unlock_and_continue;
}
/*
* The page may have been busied during the
* blocking in vput(); We don't move the
* page back onto the end of the queue so that
* statistics are more correct if we don't.
*/
if (m->busy || (m->flags & PG_BUSY)) {
goto unlock_and_continue;
}
/*
* If the page has become held it might
* be undergoing I/O, so skip it
*/
if (m->hold_count) {
vm_pageq_requeue(m);
if (object->flags & OBJ_MIGHTBEDIRTY)
vnodes_skipped++;
goto unlock_and_continue;
}
}
/*
* If a page is dirty, then it is either being washed
* (but not yet cleaned) or it is still in the
* laundry. If it is still in the laundry, then we
* start the cleaning operation.
*
* This operation may cluster, invalidating the 'next'
* pointer. To prevent an inordinate number of
* restarts we use our marker to remember our place.
*
* decrement page_shortage on success to account for
* the (future) cleaned page. Otherwise we could wind
* up laundering or cleaning too many pages.
*/
TAILQ_INSERT_AFTER(&vm_page_queues[PQ_INACTIVE].pl, m, &marker, pageq);
if (vm_pageout_clean(m) != 0) {
--page_shortage;
--maxlaunder;
}
next = TAILQ_NEXT(&marker, pageq);
TAILQ_REMOVE(&vm_page_queues[PQ_INACTIVE].pl, &marker, pageq);
unlock_and_continue:
VM_OBJECT_UNLOCK(object);
if (vp) {
vm_page_unlock_queues();
vput(vp);
vn_finished_write(mp);
vm_page_lock_queues();
}
continue;
}
VM_OBJECT_UNLOCK(object);
}
/*
* Compute the number of pages we want to try to move from the
* active queue to the inactive queue.
*/
page_shortage = vm_paging_target() +
cnt.v_inactive_target - cnt.v_inactive_count;
page_shortage += addl_page_shortage;
/*
* Scan the active queue for things we can deactivate. We nominally
* track the per-page activity counter and use it to locate
* deactivation candidates.
*/
pcount = cnt.v_active_count;
m = TAILQ_FIRST(&vm_page_queues[PQ_ACTIVE].pl);
while ((m != NULL) && (pcount-- > 0) && (page_shortage > 0)) {
KASSERT(m->queue == PQ_ACTIVE,
("vm_pageout_scan: page %p isn't active", m));
next = TAILQ_NEXT(m, pageq);
/*
* Don't deactivate pages that are busy.
*/
if ((m->busy != 0) ||
(m->flags & PG_BUSY) ||
(m->hold_count != 0)) {
vm_pageq_requeue(m);
m = next;
continue;
}
/*
* The count for pagedaemon pages is done after checking the
* page for eligibility...
*/
cnt.v_pdpages++;
/*
* Check to see "how much" the page has been used.
*/
actcount = 0;
if (m->object->ref_count != 0) {
if (m->flags & PG_REFERENCED) {
actcount += 1;
}
actcount += pmap_ts_referenced(m);
if (actcount) {
m->act_count += ACT_ADVANCE + actcount;
if (m->act_count > ACT_MAX)
m->act_count = ACT_MAX;
}
}
/*
* Since we have "tested" this bit, we need to clear it now.
*/
vm_page_flag_clear(m, PG_REFERENCED);
/*
* Only if an object is currently being used, do we use the
* page activation count stats.
*/
if (actcount && (m->object->ref_count != 0)) {
vm_pageq_requeue(m);
} else {
m->act_count -= min(m->act_count, ACT_DECLINE);
if (vm_pageout_algorithm ||
m->object->ref_count == 0 ||
m->act_count == 0) {
page_shortage--;
if (m->object->ref_count == 0) {
pmap_remove_all(m);
if (m->dirty == 0)
vm_page_cache(m);
else
vm_page_deactivate(m);
} else {
vm_page_deactivate(m);
}
} else {
vm_pageq_requeue(m);
}
}
m = next;
}
/*
* We try to maintain some *really* free pages, this allows interrupt
* code to be guaranteed space. Since both cache and free queues
* are considered basically 'free', moving pages from cache to free
* does not effect other calculations.
*/
while (cnt.v_free_count < cnt.v_free_reserved) {
static int cache_rover = 0;
if ((m = vm_page_select_cache(cache_rover)) == NULL)
break;
cache_rover = (m->pc + PQ_PRIME2) & PQ_L2_MASK;
object = m->object;
VM_OBJECT_LOCK_ASSERT(object, MA_OWNED);
vm_page_busy(m);
vm_page_free(m);
VM_OBJECT_UNLOCK(object);
cnt.v_dfree++;
}
vm_page_unlock_queues();
#if !defined(NO_SWAPPING)
/*
* Idle process swapout -- run once per second.
*/
if (vm_swap_idle_enabled) {
static long lsec;
if (time_second != lsec) {
vm_pageout_req_swapout |= VM_SWAP_IDLE;
vm_req_vmdaemon();
lsec = time_second;
}
}
#endif
/*
* If we didn't get enough free pages, and we have skipped a vnode
* in a writeable object, wakeup the sync daemon. And kick swapout
* if we did not get enough free pages.
*/
if (vm_paging_target() > 0) {
if (vnodes_skipped && vm_page_count_min())
(void) speedup_syncer();
#if !defined(NO_SWAPPING)
if (vm_swap_enabled && vm_page_count_target()) {
vm_req_vmdaemon();
vm_pageout_req_swapout |= VM_SWAP_NORMAL;
}
#endif
}
/*
* If we are critically low on one of RAM or swap and low on
* the other, kill the largest process. However, we avoid
* doing this on the first pass in order to give ourselves a
* chance to flush out dirty vnode-backed pages and to allow
* active pages to be moved to the inactive queue and reclaimed.
*
* We keep the process bigproc locked once we find it to keep anyone
* from messing with it; however, there is a possibility of
* deadlock if process B is bigproc and one of it's child processes
* attempts to propagate a signal to B while we are waiting for A's
* lock while walking this list. To avoid this, we don't block on
* the process lock but just skip a process if it is already locked.
*/
if (pass != 0 &&
((swap_pager_avail < 64 && vm_page_count_min()) ||
(swap_pager_full && vm_paging_target() > 0))) {
bigproc = NULL;
bigsize = 0;
sx_slock(&allproc_lock);
FOREACH_PROC_IN_SYSTEM(p) {
int breakout;
if (PROC_TRYLOCK(p) == 0)
continue;
/*
* If this is a system or protected process, skip it.
*/
if ((p->p_flag & P_SYSTEM) || (p->p_pid == 1) ||
(p->p_flag & P_PROTECTED) ||
((p->p_pid < 48) && (swap_pager_avail != 0))) {
PROC_UNLOCK(p);
continue;
}
/*
* If the process is in a non-running type state,
* don't touch it. Check all the threads individually.
*/
mtx_lock_spin(&sched_lock);
breakout = 0;
FOREACH_THREAD_IN_PROC(p, td) {
if (!TD_ON_RUNQ(td) &&
!TD_IS_RUNNING(td) &&
!TD_IS_SLEEPING(td)) {
breakout = 1;
break;
}
}
if (breakout) {
mtx_unlock_spin(&sched_lock);
PROC_UNLOCK(p);
continue;
}
mtx_unlock_spin(&sched_lock);
/*
* get the process size
*/
if (!vm_map_trylock_read(&p->p_vmspace->vm_map)) {
PROC_UNLOCK(p);
continue;
}
size = vmspace_swap_count(p->p_vmspace);
vm_map_unlock_read(&p->p_vmspace->vm_map);
size += vmspace_resident_count(p->p_vmspace);
/*
* if the this process is bigger than the biggest one
* remember it.
*/
if (size > bigsize) {
if (bigproc != NULL)
PROC_UNLOCK(bigproc);
bigproc = p;
bigsize = size;
} else
PROC_UNLOCK(p);
}
sx_sunlock(&allproc_lock);
if (bigproc != NULL) {
killproc(bigproc, "out of swap space");
mtx_lock_spin(&sched_lock);
sched_nice(bigproc, PRIO_MIN);
mtx_unlock_spin(&sched_lock);
PROC_UNLOCK(bigproc);
wakeup(&cnt.v_free_count);
}
}
mtx_unlock(&Giant);
}
/*
* This routine tries to maintain the pseudo LRU active queue,
* so that during long periods of time where there is no paging,
* that some statistic accumulation still occurs. This code
* helps the situation where paging just starts to occur.
*/
static void
vm_pageout_page_stats()
{
vm_page_t m,next;
int pcount,tpcount; /* Number of pages to check */
static int fullintervalcount = 0;
int page_shortage;
mtx_assert(&vm_page_queue_mtx, MA_OWNED);
page_shortage =
(cnt.v_inactive_target + cnt.v_cache_max + cnt.v_free_min) -
(cnt.v_free_count + cnt.v_inactive_count + cnt.v_cache_count);
if (page_shortage <= 0)
return;
pcount = cnt.v_active_count;
fullintervalcount += vm_pageout_stats_interval;
if (fullintervalcount < vm_pageout_full_stats_interval) {
tpcount = (vm_pageout_stats_max * cnt.v_active_count) / cnt.v_page_count;
if (pcount > tpcount)
pcount = tpcount;
} else {
fullintervalcount = 0;
}
m = TAILQ_FIRST(&vm_page_queues[PQ_ACTIVE].pl);
while ((m != NULL) && (pcount-- > 0)) {
int actcount;
KASSERT(m->queue == PQ_ACTIVE,
("vm_pageout_page_stats: page %p isn't active", m));
next = TAILQ_NEXT(m, pageq);
/*
* Don't deactivate pages that are busy.
*/
if ((m->busy != 0) ||
(m->flags & PG_BUSY) ||
(m->hold_count != 0)) {
vm_pageq_requeue(m);
m = next;
continue;
}
actcount = 0;
if (m->flags & PG_REFERENCED) {
vm_page_flag_clear(m, PG_REFERENCED);
actcount += 1;
}
actcount += pmap_ts_referenced(m);
if (actcount) {
m->act_count += ACT_ADVANCE + actcount;
if (m->act_count > ACT_MAX)
m->act_count = ACT_MAX;
vm_pageq_requeue(m);
} else {
if (m->act_count == 0) {
/*
* We turn off page access, so that we have
* more accurate RSS stats. We don't do this
* in the normal page deactivation when the
* system is loaded VM wise, because the
* cost of the large number of page protect
* operations would be higher than the value
* of doing the operation.
*/
pmap_remove_all(m);
vm_page_deactivate(m);
} else {
m->act_count -= min(m->act_count, ACT_DECLINE);
vm_pageq_requeue(m);
}
}
m = next;
}
}
/*
* vm_pageout is the high level pageout daemon.
*/
static void
vm_pageout()
{
int error, pass;
/*
* Initialize some paging parameters.
*/
cnt.v_interrupt_free_min = 2;
if (cnt.v_page_count < 2000)
vm_pageout_page_count = 8;
/*
* v_free_reserved needs to include enough for the largest
* swap pager structures plus enough for any pv_entry structs
* when paging.
*/
if (cnt.v_page_count > 1024)
cnt.v_free_min = 4 + (cnt.v_page_count - 1024) / 200;
else
cnt.v_free_min = 4;
cnt.v_pageout_free_min = (2*MAXBSIZE)/PAGE_SIZE +
cnt.v_interrupt_free_min;
cnt.v_free_reserved = vm_pageout_page_count +
cnt.v_pageout_free_min + (cnt.v_page_count / 768) + PQ_L2_SIZE;
cnt.v_free_severe = cnt.v_free_min / 2;
cnt.v_free_min += cnt.v_free_reserved;
cnt.v_free_severe += cnt.v_free_reserved;
/*
* v_free_target and v_cache_min control pageout hysteresis. Note
* that these are more a measure of the VM cache queue hysteresis
* then the VM free queue. Specifically, v_free_target is the
* high water mark (free+cache pages).
*
* v_free_reserved + v_cache_min (mostly means v_cache_min) is the
* low water mark, while v_free_min is the stop. v_cache_min must
* be big enough to handle memory needs while the pageout daemon
* is signalled and run to free more pages.
*/
if (cnt.v_free_count > 6144)
cnt.v_free_target = 4 * cnt.v_free_min + cnt.v_free_reserved;
else
cnt.v_free_target = 2 * cnt.v_free_min + cnt.v_free_reserved;
if (cnt.v_free_count > 2048) {
cnt.v_cache_min = cnt.v_free_target;
cnt.v_cache_max = 2 * cnt.v_cache_min;
cnt.v_inactive_target = (3 * cnt.v_free_target) / 2;
} else {
cnt.v_cache_min = 0;
cnt.v_cache_max = 0;
cnt.v_inactive_target = cnt.v_free_count / 4;
}
if (cnt.v_inactive_target > cnt.v_free_count / 3)
cnt.v_inactive_target = cnt.v_free_count / 3;
/* XXX does not really belong here */
if (vm_page_max_wired == 0)
vm_page_max_wired = cnt.v_free_count / 3;
if (vm_pageout_stats_max == 0)
vm_pageout_stats_max = cnt.v_free_target;
/*
* Set interval in seconds for stats scan.
*/
if (vm_pageout_stats_interval == 0)
vm_pageout_stats_interval = 5;
if (vm_pageout_full_stats_interval == 0)
vm_pageout_full_stats_interval = vm_pageout_stats_interval * 4;
swap_pager_swap_init();
pass = 0;
/*
* The pageout daemon is never done, so loop forever.
*/
while (TRUE) {
vm_page_lock_queues();
/*
* If we have enough free memory, wakeup waiters. Do
* not clear vm_pages_needed until we reach our target,
* otherwise we may be woken up over and over again and
* waste a lot of cpu.
*/
if (vm_pages_needed && !vm_page_count_min()) {
if (!vm_paging_needed())
vm_pages_needed = 0;
wakeup(&cnt.v_free_count);
}
if (vm_pages_needed) {
/*
* Still not done, take a second pass without waiting
* (unlimited dirty cleaning), otherwise sleep a bit
* and try again.
*/
++pass;
if (pass > 1)
msleep(&vm_pages_needed, &vm_page_queue_mtx, PVM,
"psleep", hz/2);
} else {
/*
* Good enough, sleep & handle stats. Prime the pass
* for the next run.
*/
if (pass > 1)
pass = 1;
else
pass = 0;
error = msleep(&vm_pages_needed, &vm_page_queue_mtx, PVM,
"psleep", vm_pageout_stats_interval * hz);
if (error && !vm_pages_needed) {
pass = 0;
vm_pageout_page_stats();
vm_page_unlock_queues();
continue;
}
}
if (vm_pages_needed)
cnt.v_pdwakeups++;
vm_page_unlock_queues();
vm_pageout_scan(pass);
}
}
/*
* Unless the page queue lock is held by the caller, this function
* should be regarded as advisory. Specifically, the caller should
* not msleep() on &cnt.v_free_count following this function unless
* the page queue lock is held until the msleep() is performed.
*/
void
pagedaemon_wakeup()
{
if (!vm_pages_needed && curthread->td_proc != pageproc) {
vm_pages_needed = 1;
wakeup(&vm_pages_needed);
}
}
#if !defined(NO_SWAPPING)
static void
vm_req_vmdaemon()
{
static int lastrun = 0;
if ((ticks > (lastrun + hz)) || (ticks < lastrun)) {
wakeup(&vm_daemon_needed);
lastrun = ticks;
}
}
static void
vm_daemon()
{
struct rlimit rsslim;
struct proc *p;
struct thread *td;
int breakout;
mtx_lock(&Giant);
while (TRUE) {
tsleep(&vm_daemon_needed, PPAUSE, "psleep", 0);
if (vm_pageout_req_swapout) {
swapout_procs(vm_pageout_req_swapout);
vm_pageout_req_swapout = 0;
}
/*
* scan the processes for exceeding their rlimits or if
* process is swapped out -- deactivate pages
*/
sx_slock(&allproc_lock);
LIST_FOREACH(p, &allproc, p_list) {
vm_pindex_t limit, size;
/*
* if this is a system process or if we have already
* looked at this process, skip it.
*/
PROC_LOCK(p);
if (p->p_flag & (P_SYSTEM | P_WEXIT)) {
PROC_UNLOCK(p);
continue;
}
/*
* if the process is in a non-running type state,
* don't touch it.
*/
mtx_lock_spin(&sched_lock);
breakout = 0;
FOREACH_THREAD_IN_PROC(p, td) {
if (!TD_ON_RUNQ(td) &&
!TD_IS_RUNNING(td) &&
!TD_IS_SLEEPING(td)) {
breakout = 1;
break;
}
}
mtx_unlock_spin(&sched_lock);
if (breakout) {
PROC_UNLOCK(p);
continue;
}
/*
* get a limit
*/
lim_rlimit(p, RLIMIT_RSS, &rsslim);
limit = OFF_TO_IDX(
qmin(rsslim.rlim_cur, rsslim.rlim_max));
/*
* let processes that are swapped out really be
* swapped out set the limit to nothing (will force a
* swap-out.)
*/
if ((p->p_sflag & PS_INMEM) == 0)
limit = 0; /* XXX */
PROC_UNLOCK(p);
size = vmspace_resident_count(p->p_vmspace);
if (limit >= 0 && size >= limit) {
vm_pageout_map_deactivate_pages(
&p->p_vmspace->vm_map, limit);
}
}
sx_sunlock(&allproc_lock);
}
}
#endif /* !defined(NO_SWAPPING) */