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freebsd-skq/sys/vm/vm_pageout.c
Alan Cox 791444089f Correct errors and clean up the comments on the active queue scan. 
Eliminate some unnecessary blank lines.

Reviewed by:	kib, markj
MFC after:	1 week
2016-08-12 03:22:58 +00:00

1849 lines
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/*-
* 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.
* Copyright (c) 2005 Yahoo! Technologies Norway AS
* 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("$FreeBSD$");
#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/mount.h>
#include <sys/racct.h>
#include <sys/resourcevar.h>
#include <sys/sched.h>
#include <sys/sdt.h>
#include <sys/signalvar.h>
#include <sys/smp.h>
#include <sys/time.h>
#include <sys/vnode.h>
#include <sys/vmmeter.h>
#include <sys/rwlock.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/vm_phys.h>
#include <vm/swap_pager.h>
#include <vm/vm_extern.h>
#include <vm/uma.h>
/*
* System initialization
*/
/* the kernel process "vm_pageout"*/
static void vm_pageout(void);
static void vm_pageout_init(void);
static int vm_pageout_clean(vm_page_t m);
static int vm_pageout_cluster(vm_page_t m);
static void vm_pageout_scan(struct vm_domain *vmd, int pass);
static void vm_pageout_mightbe_oom(struct vm_domain *vmd, int page_shortage,
int starting_page_shortage);
SYSINIT(pagedaemon_init, SI_SUB_KTHREAD_PAGE, SI_ORDER_FIRST, vm_pageout_init,
NULL);
struct proc *pageproc;
static struct kproc_desc page_kp = {
"pagedaemon",
vm_pageout,
&pageproc
};
SYSINIT(pagedaemon, SI_SUB_KTHREAD_PAGE, SI_ORDER_SECOND, kproc_start,
&page_kp);
SDT_PROVIDER_DEFINE(vm);
SDT_PROBE_DEFINE(vm, , , vm__lowmem_scan);
#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_pageout_deficit; /* Estimated number of pages deficit */
u_int vm_pageout_wakeup_thresh;
static int vm_pageout_oom_seq = 12;
bool vm_pageout_wanted; /* Event on which pageout daemon sleeps */
bool vm_pages_needed; /* Are threads waiting for free pages? */
#if !defined(NO_SWAPPING)
static int vm_pageout_req_swapout; /* XXX */
static int vm_daemon_needed;
static struct mtx vm_daemon_mtx;
/* Allow for use by vm_pageout before vm_daemon is initialized. */
MTX_SYSINIT(vm_daemon, &vm_daemon_mtx, "vm daemon", MTX_DEF);
#endif
static int vm_max_launder = 32;
static int vm_pageout_update_period;
static int defer_swap_pageouts;
static int disable_swap_pageouts;
static int lowmem_period = 10;
static time_t lowmem_uptime;
#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
static int vm_panic_on_oom = 0;
SYSCTL_INT(_vm, OID_AUTO, panic_on_oom,
CTLFLAG_RWTUN, &vm_panic_on_oom, 0,
"panic on out of memory instead of killing the largest process");
SYSCTL_INT(_vm, OID_AUTO, pageout_wakeup_thresh,
CTLFLAG_RW, &vm_pageout_wakeup_thresh, 0,
"free page threshold for waking up the pageout daemon");
SYSCTL_INT(_vm, OID_AUTO, max_launder,
CTLFLAG_RW, &vm_max_launder, 0, "Limit dirty flushes in pageout");
SYSCTL_INT(_vm, OID_AUTO, pageout_update_period,
CTLFLAG_RW, &vm_pageout_update_period, 0,
"Maximum active LRU update period");
SYSCTL_INT(_vm, OID_AUTO, lowmem_period, CTLFLAG_RW, &lowmem_period, 0,
"Low memory callback period");
#if defined(NO_SWAPPING)
SYSCTL_INT(_vm, VM_SWAPPING_ENABLED, swap_enabled,
CTLFLAG_RD, &vm_swap_enabled, 0, "Enable entire process swapout");
SYSCTL_INT(_vm, OID_AUTO, swap_idle_enabled,
CTLFLAG_RD, &vm_swap_idle_enabled, 0, "Allow swapout on idle criteria");
#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");
SYSCTL_INT(_vm, OID_AUTO, pageout_oom_seq,
CTLFLAG_RW, &vm_pageout_oom_seq, 0,
"back-to-back calls to oom detector to start OOM");
#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 */
SYSCTL_INT(_vm, OID_AUTO, max_wired,
CTLFLAG_RW, &vm_page_max_wired, 0, "System-wide limit to wired page count");
static boolean_t vm_pageout_fallback_object_lock(vm_page_t, vm_page_t *);
#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(int req);
#endif
static boolean_t vm_pageout_page_lock(vm_page_t, vm_page_t *);
/*
* Initialize a dummy page for marking the caller's place in the specified
* paging queue. In principle, this function only needs to set the flag
* PG_MARKER. Nonetheless, it write busies and initializes the hold count
* to one as safety precautions.
*/
static void
vm_pageout_init_marker(vm_page_t marker, u_short queue)
{
bzero(marker, sizeof(*marker));
marker->flags = PG_MARKER;
marker->busy_lock = VPB_SINGLE_EXCLUSIVER;
marker->queue = queue;
marker->hold_count = 1;
}
/*
* vm_pageout_fallback_object_lock:
*
* Lock vm object currently associated with `m'. VM_OBJECT_TRYWLOCK is
* known to have failed and page queue must be either PQ_ACTIVE or
* PQ_INACTIVE. To avoid lock order violation, unlock the page queue
* while locking the vm object. Use marker page to detect page queue
* changes and maintain notion of next page on page queue. Return
* TRUE if no changes were detected, FALSE otherwise. vm object is
* locked on return.
*
* This function depends on both the lock portion of struct vm_object
* and normal struct vm_page being type stable.
*/
static boolean_t
vm_pageout_fallback_object_lock(vm_page_t m, vm_page_t *next)
{
struct vm_page marker;
struct vm_pagequeue *pq;
boolean_t unchanged;
u_short queue;
vm_object_t object;
queue = m->queue;
vm_pageout_init_marker(&marker, queue);
pq = vm_page_pagequeue(m);
object = m->object;
TAILQ_INSERT_AFTER(&pq->pq_pl, m, &marker, plinks.q);
vm_pagequeue_unlock(pq);
vm_page_unlock(m);
VM_OBJECT_WLOCK(object);
vm_page_lock(m);
vm_pagequeue_lock(pq);
/*
* The page's object might have changed, and/or the page might
* have moved from its original position in the queue. If the
* page's object has changed, then the caller should abandon
* processing the page because the wrong object lock was
* acquired. Use the marker's plinks.q, not the page's, to
* determine if the page has been moved. The state of the
* page's plinks.q can be indeterminate; whereas, the marker's
* plinks.q must be valid.
*/
*next = TAILQ_NEXT(&marker, plinks.q);
unchanged = m->object == object &&
m == TAILQ_PREV(&marker, pglist, plinks.q);
KASSERT(!unchanged || m->queue == queue,
("page %p queue %d %d", m, queue, m->queue));
TAILQ_REMOVE(&pq->pq_pl, &marker, plinks.q);
return (unchanged);
}
/*
* Lock the page while holding the page queue lock. Use marker page
* to detect page queue changes and maintain notion of next page on
* page queue. Return TRUE if no changes were detected, FALSE
* otherwise. The page is locked on return. The page queue lock might
* be dropped and reacquired.
*
* This function depends on normal struct vm_page being type stable.
*/
static boolean_t
vm_pageout_page_lock(vm_page_t m, vm_page_t *next)
{
struct vm_page marker;
struct vm_pagequeue *pq;
boolean_t unchanged;
u_short queue;
vm_page_lock_assert(m, MA_NOTOWNED);
if (vm_page_trylock(m))
return (TRUE);
queue = m->queue;
vm_pageout_init_marker(&marker, queue);
pq = vm_page_pagequeue(m);
TAILQ_INSERT_AFTER(&pq->pq_pl, m, &marker, plinks.q);
vm_pagequeue_unlock(pq);
vm_page_lock(m);
vm_pagequeue_lock(pq);
/* Page queue might have changed. */
*next = TAILQ_NEXT(&marker, plinks.q);
unchanged = m == TAILQ_PREV(&marker, pglist, plinks.q);
KASSERT(!unchanged || m->queue == queue,
("page %p queue %d %d", m, queue, m->queue));
TAILQ_REMOVE(&pq->pq_pl, &marker, plinks.q);
return (unchanged);
}
/*
* Scan for pages at adjacent offsets within the given page's object that are
* eligible for laundering, form a cluster of these pages and the given page,
* and launder that cluster.
*/
static int
vm_pageout_cluster(vm_page_t m)
{
vm_object_t object;
vm_page_t mc[2 * vm_pageout_page_count], p, pb, ps;
vm_pindex_t pindex;
int ib, is, page_base, pageout_count;
vm_page_assert_locked(m);
object = m->object;
VM_OBJECT_ASSERT_WLOCKED(object);
pindex = m->pindex;
/*
* We can't clean the page if it is busy or held.
*/
vm_page_assert_unbusied(m);
KASSERT(m->hold_count == 0, ("page %p is held", m));
vm_page_unlock(m);
mc[vm_pageout_page_count] = pb = ps = m;
pageout_count = 1;
page_base = vm_pageout_page_count;
ib = 1;
is = 1;
/*
* We can cluster only if the page is not clean, busy, or held, and
* the page is inactive.
*
* During heavy mmap/modification loads the pageout
* daemon can really fragment the underlying file
* due to flushing pages out of order and not trying to
* align the clusters (which leaves sporadic 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.
*/
more:
while (ib != 0 && pageout_count < vm_pageout_page_count) {
if (ib > pindex) {
ib = 0;
break;
}
if ((p = vm_page_prev(pb)) == NULL || vm_page_busied(p)) {
ib = 0;
break;
}
vm_page_test_dirty(p);
if (p->dirty == 0) {
ib = 0;
break;
}
vm_page_lock(p);
if (p->queue != PQ_INACTIVE ||
p->hold_count != 0) { /* may be undergoing I/O */
vm_page_unlock(p);
ib = 0;
break;
}
vm_page_unlock(p);
mc[--page_base] = pb = p;
++pageout_count;
++ib;
/*
* We are at an alignment boundary. 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) {
if ((p = vm_page_next(ps)) == NULL || vm_page_busied(p))
break;
vm_page_test_dirty(p);
if (p->dirty == 0)
break;
vm_page_lock(p);
if (p->queue != PQ_INACTIVE ||
p->hold_count != 0) { /* may be undergoing I/O */
vm_page_unlock(p);
break;
}
vm_page_unlock(p);
mc[page_base + pageout_count] = ps = p;
++pageout_count;
++is;
}
/*
* If we exhausted our forward scan, continue with the reverse scan
* when possible, even past an alignment boundary. This catches
* boundary conditions.
*/
if (ib != 0 && pageout_count < vm_pageout_page_count)
goto more;
return (vm_pageout_flush(&mc[page_base], pageout_count, 0, 0, NULL,
NULL));
}
/*
* 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.
*
* Returned runlen is the count of pages between mreq and first
* page after mreq with status VM_PAGER_AGAIN.
* *eio is set to TRUE if pager returned VM_PAGER_ERROR or VM_PAGER_FAIL
* for any page in runlen set.
*/
int
vm_pageout_flush(vm_page_t *mc, int count, int flags, int mreq, int *prunlen,
boolean_t *eio)
{
vm_object_t object = mc[0]->object;
int pageout_status[count];
int numpagedout = 0;
int i, runlen;
VM_OBJECT_ASSERT_WLOCKED(object);
/*
* 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_sbusy(mc[i]);
pmap_remove_write(mc[i]);
}
vm_object_pip_add(object, count);
vm_pager_put_pages(object, mc, count, flags, pageout_status);
runlen = count - mreq;
if (eio != NULL)
*eio = FALSE;
for (i = 0; i < count; i++) {
vm_page_t mt = mc[i];
KASSERT(pageout_status[i] == VM_PAGER_PEND ||
!pmap_page_is_write_mapped(mt),
("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.
*/
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_lock(mt);
vm_page_activate(mt);
vm_page_unlock(mt);
if (eio != NULL && i >= mreq && i - mreq < runlen)
*eio = TRUE;
break;
case VM_PAGER_AGAIN:
if (i >= mreq && i - mreq < runlen)
runlen = i - mreq;
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_sunbusy(mt);
}
}
if (prunlen != NULL)
*prunlen = runlen;
return (numpagedout);
}
#if !defined(NO_SWAPPING)
/*
* vm_pageout_object_deactivate_pages
*
* Deactivate enough pages to satisfy the inactive target
* requirements.
*
* The object and map must be locked.
*/
static void
vm_pageout_object_deactivate_pages(pmap_t pmap, vm_object_t first_object,
long desired)
{
vm_object_t backing_object, object;
vm_page_t p;
int act_delta, remove_mode;
VM_OBJECT_ASSERT_LOCKED(first_object);
if ((first_object->flags & OBJ_FICTITIOUS) != 0)
return;
for (object = first_object;; object = backing_object) {
if (pmap_resident_count(pmap) <= desired)
goto unlock_return;
VM_OBJECT_ASSERT_LOCKED(object);
if ((object->flags & OBJ_UNMANAGED) != 0 ||
object->paging_in_progress != 0)
goto unlock_return;
remove_mode = 0;
if (object->shadow_count > 1)
remove_mode = 1;
/*
* Scan the object's entire memory queue.
*/
TAILQ_FOREACH(p, &object->memq, listq) {
if (pmap_resident_count(pmap) <= desired)
goto unlock_return;
if (vm_page_busied(p))
continue;
PCPU_INC(cnt.v_pdpages);
vm_page_lock(p);
if (p->wire_count != 0 || p->hold_count != 0 ||
!pmap_page_exists_quick(pmap, p)) {
vm_page_unlock(p);
continue;
}
act_delta = pmap_ts_referenced(p);
if ((p->aflags & PGA_REFERENCED) != 0) {
if (act_delta == 0)
act_delta = 1;
vm_page_aflag_clear(p, PGA_REFERENCED);
}
if (p->queue != PQ_ACTIVE && act_delta != 0) {
vm_page_activate(p);
p->act_count += act_delta;
} else if (p->queue == PQ_ACTIVE) {
if (act_delta == 0) {
p->act_count -= min(p->act_count,
ACT_DECLINE);
if (!remove_mode && p->act_count == 0) {
pmap_remove_all(p);
vm_page_deactivate(p);
} else
vm_page_requeue(p);
} else {
vm_page_activate(p);
if (p->act_count < ACT_MAX -
ACT_ADVANCE)
p->act_count += ACT_ADVANCE;
vm_page_requeue(p);
}
} else if (p->queue == PQ_INACTIVE)
pmap_remove_all(p);
vm_page_unlock(p);
}
if ((backing_object = object->backing_object) == NULL)
goto unlock_return;
VM_OBJECT_RLOCK(backing_object);
if (object != first_object)
VM_OBJECT_RUNLOCK(object);
}
unlock_return:
if (object != first_object)
VM_OBJECT_RUNLOCK(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_TRYRLOCK(obj)) {
if (obj->shadow_count <= 1 &&
(bigobj == NULL ||
bigobj->resident_page_count < obj->resident_page_count)) {
if (bigobj != NULL)
VM_OBJECT_RUNLOCK(bigobj);
bigobj = obj;
} else
VM_OBJECT_RUNLOCK(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_RUNLOCK(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_RLOCK(obj);
vm_pageout_object_deactivate_pages(map->pmap, obj, desired);
VM_OBJECT_RUNLOCK(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) */
/*
* Attempt to acquire all of the necessary locks to launder a page and
* then call through the clustering layer to PUTPAGES. Wait a short
* time for a vnode lock.
*
* Requires the page and object lock on entry, releases both before return.
* Returns 0 on success and an errno otherwise.
*/
static int
vm_pageout_clean(vm_page_t m)
{
struct vnode *vp;
struct mount *mp;
vm_object_t object;
vm_pindex_t pindex;
int error, lockmode;
vm_page_assert_locked(m);
object = m->object;
VM_OBJECT_ASSERT_WLOCKED(object);
error = 0;
vp = NULL;
mp = NULL;
/*
* 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.
*
* 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) {
vm_page_unlock(m);
vp = object->handle;
if (vp->v_type == VREG &&
vn_start_write(vp, &mp, V_NOWAIT) != 0) {
mp = NULL;
error = EDEADLK;
goto unlock_all;
}
KASSERT(mp != NULL,
("vp %p with NULL v_mount", vp));
vm_object_reference_locked(object);
pindex = m->pindex;
VM_OBJECT_WUNLOCK(object);
lockmode = MNT_SHARED_WRITES(vp->v_mount) ?
LK_SHARED : LK_EXCLUSIVE;
if (vget(vp, lockmode | LK_TIMELOCK, curthread)) {
vp = NULL;
error = EDEADLK;
goto unlock_mp;
}
VM_OBJECT_WLOCK(object);
vm_page_lock(m);
/*
* While the object and page were unlocked, the page
* may have been:
* (1) moved to a different queue,
* (2) reallocated to a different object,
* (3) reallocated to a different offset, or
* (4) cleaned.
*/
if (m->queue != PQ_INACTIVE || m->object != object ||
m->pindex != pindex || m->dirty == 0) {
vm_page_unlock(m);
error = ENXIO;
goto unlock_all;
}
/*
* The page may have been busied or held while the object
* and page locks were released.
*/
if (vm_page_busied(m) || m->hold_count != 0) {
vm_page_unlock(m);
error = EBUSY;
goto unlock_all;
}
}
/*
* 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.
*/
if (vm_pageout_cluster(m) == 0)
error = EIO;
unlock_all:
VM_OBJECT_WUNLOCK(object);
unlock_mp:
vm_page_lock_assert(m, MA_NOTOWNED);
if (mp != NULL) {
if (vp != NULL)
vput(vp);
vm_object_deallocate(object);
vn_finished_write(mp);
}
return (error);
}
/*
* vm_pageout_scan does the dirty work for the pageout daemon.
*
* pass 0 - Update active LRU/deactivate pages
* pass 1 - Free inactive pages
* pass 2 - Launder dirty pages
*/
static void
vm_pageout_scan(struct vm_domain *vmd, int pass)
{
vm_page_t m, next;
struct vm_pagequeue *pq;
vm_object_t object;
long min_scan;
int act_delta, addl_page_shortage, deficit, error, maxlaunder, maxscan;
int page_shortage, scan_tick, scanned, starting_page_shortage;
int vnodes_skipped;
boolean_t pageout_ok, queue_locked;
/*
* If we need to reclaim memory ask kernel caches to return
* some. We rate limit to avoid thrashing.
*/
if (vmd == &vm_dom[0] && pass > 0 &&
(time_uptime - lowmem_uptime) >= lowmem_period) {
/*
* Decrease registered cache sizes.
*/
SDT_PROBE0(vm, , , vm__lowmem_scan);
EVENTHANDLER_INVOKE(vm_lowmem, 0);
/*
* We do this explicitly after the caches have been
* drained above.
*/
uma_reclaim();
lowmem_uptime = time_uptime;
}
/*
* The addl_page_shortage is the number of temporarily
* stuck pages in the inactive queue. In other words, the
* number of pages from the inactive count that should be
* discounted in setting the target for the active queue scan.
*/
addl_page_shortage = 0;
/*
* Calculate the number of pages that we want to free.
*/
if (pass > 0) {
deficit = atomic_readandclear_int(&vm_pageout_deficit);
page_shortage = vm_paging_target() + deficit;
} else
page_shortage = deficit = 0;
starting_page_shortage = page_shortage;
/*
* 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 > 1)
maxlaunder = 10000;
vnodes_skipped = 0;
/*
* Start scanning the inactive queue for pages that we can free. The
* scan will stop when we reach the target or we have scanned the
* entire queue. (Note that m->act_count is not used to make
* decisions for the inactive queue, only for the active queue.)
*/
pq = &vmd->vmd_pagequeues[PQ_INACTIVE];
maxscan = pq->pq_cnt;
vm_pagequeue_lock(pq);
queue_locked = TRUE;
for (m = TAILQ_FIRST(&pq->pq_pl);
m != NULL && maxscan-- > 0 && page_shortage > 0;
m = next) {
vm_pagequeue_assert_locked(pq);
KASSERT(queue_locked, ("unlocked inactive queue"));
KASSERT(m->queue == PQ_INACTIVE, ("Inactive queue %p", m));
PCPU_INC(cnt.v_pdpages);
next = TAILQ_NEXT(m, plinks.q);
/*
* skip marker pages
*/
if (m->flags & PG_MARKER)
continue;
KASSERT((m->flags & PG_FICTITIOUS) == 0,
("Fictitious page %p cannot be in inactive queue", m));
KASSERT((m->oflags & VPO_UNMANAGED) == 0,
("Unmanaged page %p cannot be in inactive queue", m));
/*
* The page or object lock acquisitions fail if the
* page was removed from the queue or moved to a
* different position within the queue. In either
* case, addl_page_shortage should not be incremented.
*/
if (!vm_pageout_page_lock(m, &next))
goto unlock_page;
else if (m->hold_count != 0) {
/*
* Held pages are essentially stuck in the
* queue. So, they ought to be discounted
* from the inactive count. See the
* calculation of the page_shortage for the
* loop over the active queue below.
*/
addl_page_shortage++;
goto unlock_page;
}
object = m->object;
if (!VM_OBJECT_TRYWLOCK(object)) {
if (!vm_pageout_fallback_object_lock(m, &next))
goto unlock_object;
else if (m->hold_count != 0) {
addl_page_shortage++;
goto unlock_object;
}
}
if (vm_page_busied(m)) {
/*
* Don't mess with busy pages. Leave them at
* the front of the queue. Most likely, they
* are being paged out and will leave the
* queue shortly after the scan finishes. So,
* they ought to be discounted from the
* inactive count.
*/
addl_page_shortage++;
unlock_object:
VM_OBJECT_WUNLOCK(object);
unlock_page:
vm_page_unlock(m);
continue;
}
KASSERT(m->hold_count == 0, ("Held page %p", m));
/*
* We unlock the inactive page queue, invalidating the
* 'next' pointer. Use our marker to remember our
* place.
*/
TAILQ_INSERT_AFTER(&pq->pq_pl, m, &vmd->vmd_marker, plinks.q);
vm_pagequeue_unlock(pq);
queue_locked = FALSE;
/*
* Invalid pages can be easily freed. They cannot be
* mapped, vm_page_free() asserts this.
*/
if (m->valid == 0)
goto free_page;
/*
* If the page has been referenced and the object is not dead,
* reactivate or requeue the page depending on whether the
* object is mapped.
*/
if ((m->aflags & PGA_REFERENCED) != 0) {
vm_page_aflag_clear(m, PGA_REFERENCED);
act_delta = 1;
} else
act_delta = 0;
if (object->ref_count != 0) {
act_delta += pmap_ts_referenced(m);
} else {
KASSERT(!pmap_page_is_mapped(m),
("vm_pageout_scan: page %p is mapped", m));
}
if (act_delta != 0) {
if (object->ref_count != 0) {
vm_page_activate(m);
/*
* Increase the activation count if the page
* was referenced while in the inactive queue.
* This makes it less likely that the page will
* be returned prematurely to the inactive
* queue.
*/
m->act_count += act_delta + ACT_ADVANCE;
goto drop_page;
} else if ((object->flags & OBJ_DEAD) == 0)
goto requeue_page;
}
/*
* If the page appears to be clean at the machine-independent
* layer, then remove all of its mappings from the pmap in
* anticipation of freeing it. If, however, any of the page's
* mappings allow write access, then the page may still be
* modified until the last of those mappings are removed.
*/
if (object->ref_count != 0) {
vm_page_test_dirty(m);
if (m->dirty == 0)
pmap_remove_all(m);
}
if (m->dirty == 0) {
/*
* Clean pages can be freed.
*/
free_page:
vm_page_free(m);
PCPU_INC(cnt.v_dfree);
--page_shortage;
} else if ((object->flags & OBJ_DEAD) != 0) {
/*
* Leave dirty pages from dead objects at the front of
* the queue. They are being paged out and freed by
* the thread that destroyed the object. They will
* leave the queue shortly after the scan finishes, so
* they should be discounted from the inactive count.
*/
addl_page_shortage++;
} else if ((m->flags & PG_WINATCFLS) == 0 && pass < 2) {
/*
* Dirty pages need to be paged out, but flushing
* a page is extremely expensive versus 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.
*/
m->flags |= PG_WINATCFLS;
requeue_page:
vm_pagequeue_lock(pq);
queue_locked = TRUE;
vm_page_requeue_locked(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.
*/
if (object->type != OBJT_SWAP &&
object->type != OBJT_DEFAULT)
pageout_ok = TRUE;
else if (disable_swap_pageouts)
pageout_ok = FALSE;
else if (defer_swap_pageouts)
pageout_ok = vm_page_count_min();
else
pageout_ok = TRUE;
if (!pageout_ok)
goto requeue_page;
error = vm_pageout_clean(m);
/*
* Decrement page_shortage on success to account for
* the (future) cleaned page. Otherwise we could wind
* up laundering or cleaning too many pages.
*/
if (error == 0) {
page_shortage--;
maxlaunder--;
} else if (error == EDEADLK) {
pageout_lock_miss++;
vnodes_skipped++;
} else if (error == EBUSY) {
addl_page_shortage++;
}
vm_page_lock_assert(m, MA_NOTOWNED);
goto relock_queue;
}
drop_page:
vm_page_unlock(m);
VM_OBJECT_WUNLOCK(object);
relock_queue:
if (!queue_locked) {
vm_pagequeue_lock(pq);
queue_locked = TRUE;
}
next = TAILQ_NEXT(&vmd->vmd_marker, plinks.q);
TAILQ_REMOVE(&pq->pq_pl, &vmd->vmd_marker, plinks.q);
}
vm_pagequeue_unlock(pq);
#if !defined(NO_SWAPPING)
/*
* Wakeup the swapout daemon if we didn't free the targeted number of
* pages.
*/
if (vm_swap_enabled && page_shortage > 0)
vm_req_vmdaemon(VM_SWAP_NORMAL);
#endif
/*
* Wakeup the sync daemon if we skipped a vnode in a writeable object
* and we didn't free enough pages.
*/
if (vnodes_skipped > 0 && page_shortage > vm_cnt.v_free_target -
vm_cnt.v_free_min)
(void)speedup_syncer();
/*
* If the inactive queue scan fails repeatedly to meet its
* target, kill the largest process.
*/
vm_pageout_mightbe_oom(vmd, page_shortage, starting_page_shortage);
/*
* Compute the number of pages we want to try to move from the
* active queue to the inactive queue.
*/
page_shortage = vm_cnt.v_inactive_target - vm_cnt.v_inactive_count +
vm_paging_target() + deficit + addl_page_shortage;
pq = &vmd->vmd_pagequeues[PQ_ACTIVE];
vm_pagequeue_lock(pq);
maxscan = pq->pq_cnt;
/*
* If we're just idle polling attempt to visit every
* active page within 'update_period' seconds.
*/
scan_tick = ticks;
if (vm_pageout_update_period != 0) {
min_scan = pq->pq_cnt;
min_scan *= scan_tick - vmd->vmd_last_active_scan;
min_scan /= hz * vm_pageout_update_period;
} else
min_scan = 0;
if (min_scan > 0 || (page_shortage > 0 && maxscan > 0))
vmd->vmd_last_active_scan = scan_tick;
/*
* Scan the active queue for pages that can be deactivated. Update
* the per-page activity counter and use it to identify deactivation
* candidates. Held pages may be deactivated.
*/
for (m = TAILQ_FIRST(&pq->pq_pl), scanned = 0; m != NULL && (scanned <
min_scan || (page_shortage > 0 && scanned < maxscan)); m = next,
scanned++) {
KASSERT(m->queue == PQ_ACTIVE,
("vm_pageout_scan: page %p isn't active", m));
next = TAILQ_NEXT(m, plinks.q);
if ((m->flags & PG_MARKER) != 0)
continue;
KASSERT((m->flags & PG_FICTITIOUS) == 0,
("Fictitious page %p cannot be in active queue", m));
KASSERT((m->oflags & VPO_UNMANAGED) == 0,
("Unmanaged page %p cannot be in active queue", m));
if (!vm_pageout_page_lock(m, &next)) {
vm_page_unlock(m);
continue;
}
/*
* The count for page daemon pages is updated after checking
* the page for eligibility.
*/
PCPU_INC(cnt.v_pdpages);
/*
* Check to see "how much" the page has been used.
*/
if ((m->aflags & PGA_REFERENCED) != 0) {
vm_page_aflag_clear(m, PGA_REFERENCED);
act_delta = 1;
} else
act_delta = 0;
/*
* Perform an unsynchronized object ref count check. While
* the page lock ensures that the page is not reallocated to
* another object, in particular, one with unmanaged mappings
* that cannot support pmap_ts_referenced(), two races are,
* nonetheless, possible:
* 1) The count was transitioning to zero, but we saw a non-
* zero value. pmap_ts_referenced() will return zero
* because the page is not mapped.
* 2) The count was transitioning to one, but we saw zero.
* This race delays the detection of a new reference. At
* worst, we will deactivate and reactivate the page.
*/
if (m->object->ref_count != 0)
act_delta += pmap_ts_referenced(m);
/*
* Advance or decay the act_count based on recent usage.
*/
if (act_delta != 0) {
m->act_count += ACT_ADVANCE + act_delta;
if (m->act_count > ACT_MAX)
m->act_count = ACT_MAX;
} else
m->act_count -= min(m->act_count, ACT_DECLINE);
/*
* Move this page to the tail of the active or inactive
* queue depending on usage.
*/
if (m->act_count == 0) {
/* Dequeue to avoid later lock recursion. */
vm_page_dequeue_locked(m);
vm_page_deactivate(m);
page_shortage--;
} else
vm_page_requeue_locked(m);
vm_page_unlock(m);
}
vm_pagequeue_unlock(pq);
#if !defined(NO_SWAPPING)
/*
* Idle process swapout -- run once per second when we are reclaiming
* pages.
*/
if (vm_swap_idle_enabled && pass > 0) {
static long lsec;
if (time_second != lsec) {
vm_req_vmdaemon(VM_SWAP_IDLE);
lsec = time_second;
}
}
#endif
}
static int vm_pageout_oom_vote;
/*
* The pagedaemon threads randlomly select one to perform the
* OOM. Trying to kill processes before all pagedaemons
* failed to reach free target is premature.
*/
static void
vm_pageout_mightbe_oom(struct vm_domain *vmd, int page_shortage,
int starting_page_shortage)
{
int old_vote;
if (starting_page_shortage <= 0 || starting_page_shortage !=
page_shortage)
vmd->vmd_oom_seq = 0;
else
vmd->vmd_oom_seq++;
if (vmd->vmd_oom_seq < vm_pageout_oom_seq) {
if (vmd->vmd_oom) {
vmd->vmd_oom = FALSE;
atomic_subtract_int(&vm_pageout_oom_vote, 1);
}
return;
}
/*
* Do not follow the call sequence until OOM condition is
* cleared.
*/
vmd->vmd_oom_seq = 0;
if (vmd->vmd_oom)
return;
vmd->vmd_oom = TRUE;
old_vote = atomic_fetchadd_int(&vm_pageout_oom_vote, 1);
if (old_vote != vm_ndomains - 1)
return;
/*
* The current pagedaemon thread is the last in the quorum to
* start OOM. Initiate the selection and signaling of the
* victim.
*/
vm_pageout_oom(VM_OOM_MEM);
/*
* After one round of OOM terror, recall our vote. On the
* next pass, current pagedaemon would vote again if the low
* memory condition is still there, due to vmd_oom being
* false.
*/
vmd->vmd_oom = FALSE;
atomic_subtract_int(&vm_pageout_oom_vote, 1);
}
/*
* The OOM killer is the page daemon's action of last resort when
* memory allocation requests have been stalled for a prolonged period
* of time because it cannot reclaim memory. This function computes
* the approximate number of physical pages that could be reclaimed if
* the specified address space is destroyed.
*
* Private, anonymous memory owned by the address space is the
* principal resource that we expect to recover after an OOM kill.
* Since the physical pages mapped by the address space's COW entries
* are typically shared pages, they are unlikely to be released and so
* they are not counted.
*
* To get to the point where the page daemon runs the OOM killer, its
* efforts to write-back vnode-backed pages may have stalled. This
* could be caused by a memory allocation deadlock in the write path
* that might be resolved by an OOM kill. Therefore, physical pages
* belonging to vnode-backed objects are counted, because they might
* be freed without being written out first if the address space holds
* the last reference to an unlinked vnode.
*
* Similarly, physical pages belonging to OBJT_PHYS objects are
* counted because the address space might hold the last reference to
* the object.
*/
static long
vm_pageout_oom_pagecount(struct vmspace *vmspace)
{
vm_map_t map;
vm_map_entry_t entry;
vm_object_t obj;
long res;
map = &vmspace->vm_map;
KASSERT(!map->system_map, ("system map"));
sx_assert(&map->lock, SA_LOCKED);
res = 0;
for (entry = map->header.next; entry != &map->header;
entry = entry->next) {
if ((entry->eflags & MAP_ENTRY_IS_SUB_MAP) != 0)
continue;
obj = entry->object.vm_object;
if (obj == NULL)
continue;
if ((entry->eflags & MAP_ENTRY_NEEDS_COPY) != 0 &&
obj->ref_count != 1)
continue;
switch (obj->type) {
case OBJT_DEFAULT:
case OBJT_SWAP:
case OBJT_PHYS:
case OBJT_VNODE:
res += obj->resident_page_count;
break;
}
}
return (res);
}
void
vm_pageout_oom(int shortage)
{
struct proc *p, *bigproc;
vm_offset_t size, bigsize;
struct thread *td;
struct vmspace *vm;
/*
* 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.
*/
bigproc = NULL;
bigsize = 0;
sx_slock(&allproc_lock);
FOREACH_PROC_IN_SYSTEM(p) {
int breakout;
PROC_LOCK(p);
/*
* If this is a system, protected or killed process, skip it.
*/
if (p->p_state != PRS_NORMAL || (p->p_flag & (P_INEXEC |
P_PROTECTED | P_SYSTEM | P_WEXIT)) != 0 ||
p->p_pid == 1 || P_KILLED(p) ||
(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.
*/
breakout = 0;
FOREACH_THREAD_IN_PROC(p, td) {
thread_lock(td);
if (!TD_ON_RUNQ(td) &&
!TD_IS_RUNNING(td) &&
!TD_IS_SLEEPING(td) &&
!TD_IS_SUSPENDED(td) &&
!TD_IS_SWAPPED(td)) {
thread_unlock(td);
breakout = 1;
break;
}
thread_unlock(td);
}
if (breakout) {
PROC_UNLOCK(p);
continue;
}
/*
* get the process size
*/
vm = vmspace_acquire_ref(p);
if (vm == NULL) {
PROC_UNLOCK(p);
continue;
}
_PHOLD_LITE(p);
PROC_UNLOCK(p);
sx_sunlock(&allproc_lock);
if (!vm_map_trylock_read(&vm->vm_map)) {
vmspace_free(vm);
sx_slock(&allproc_lock);
PRELE(p);
continue;
}
size = vmspace_swap_count(vm);
if (shortage == VM_OOM_MEM)
size += vm_pageout_oom_pagecount(vm);
vm_map_unlock_read(&vm->vm_map);
vmspace_free(vm);
sx_slock(&allproc_lock);
/*
* If this process is bigger than the biggest one,
* remember it.
*/
if (size > bigsize) {
if (bigproc != NULL)
PRELE(bigproc);
bigproc = p;
bigsize = size;
} else {
PRELE(p);
}
}
sx_sunlock(&allproc_lock);
if (bigproc != NULL) {
if (vm_panic_on_oom != 0)
panic("out of swap space");
PROC_LOCK(bigproc);
killproc(bigproc, "out of swap space");
sched_nice(bigproc, PRIO_MIN);
_PRELE(bigproc);
PROC_UNLOCK(bigproc);
wakeup(&vm_cnt.v_free_count);
}
}
static void
vm_pageout_worker(void *arg)
{
struct vm_domain *domain;
int domidx;
domidx = (uintptr_t)arg;
domain = &vm_dom[domidx];
/*
* XXXKIB It could be useful to bind pageout daemon threads to
* the cores belonging to the domain, from which vm_page_array
* is allocated.
*/
KASSERT(domain->vmd_segs != 0, ("domain without segments"));
domain->vmd_last_active_scan = ticks;
vm_pageout_init_marker(&domain->vmd_marker, PQ_INACTIVE);
vm_pageout_init_marker(&domain->vmd_inacthead, PQ_INACTIVE);
TAILQ_INSERT_HEAD(&domain->vmd_pagequeues[PQ_INACTIVE].pq_pl,
&domain->vmd_inacthead, plinks.q);
/*
* The pageout daemon worker is never done, so loop forever.
*/
while (TRUE) {
mtx_lock(&vm_page_queue_free_mtx);
/*
* Generally, after a level >= 1 scan, if there are enough
* free pages to wakeup the waiters, then they are already
* awake. A call to vm_page_free() during the scan awakened
* them. However, in the following case, this wakeup serves
* to bound the amount of time that a thread might wait.
* Suppose a thread's call to vm_page_alloc() fails, but
* before that thread calls VM_WAIT, enough pages are freed by
* other threads to alleviate the free page shortage. The
* thread will, nonetheless, wait until another page is freed
* or this wakeup is performed.
*/
if (vm_pages_needed && !vm_page_count_min()) {
vm_pages_needed = false;
wakeup(&vm_cnt.v_free_count);
}
/*
* Do not clear vm_pageout_wanted until we reach our target.
* Otherwise, we may be awakened over and over again, wasting
* CPU time.
*/
if (vm_pageout_wanted && !vm_paging_needed())
vm_pageout_wanted = false;
/*
* Might the page daemon receive a wakeup call?
*/
if (vm_pageout_wanted) {
/*
* No. Either vm_pageout_wanted was set by another
* thread during the previous scan, which must have
* been a level 0 scan, or vm_pageout_wanted was
* already set and the scan failed to free enough
* pages. If we haven't yet performed a level >= 2
* scan (unlimited dirty cleaning), then upgrade the
* level and scan again now. Otherwise, sleep a bit
* and try again later.
*/
mtx_unlock(&vm_page_queue_free_mtx);
if (domain->vmd_pass > 1)
pause("psleep", hz / 2);
domain->vmd_pass++;
} else {
/*
* Yes. Sleep until pages need to be reclaimed or
* have their reference stats updated.
*/
if (mtx_sleep(&vm_pageout_wanted,
&vm_page_queue_free_mtx, PDROP | PVM, "psleep",
hz) == 0) {
PCPU_INC(cnt.v_pdwakeups);
domain->vmd_pass = 1;
} else
domain->vmd_pass = 0;
}
vm_pageout_scan(domain, domain->vmd_pass);
}
}
/*
* vm_pageout_init initialises basic pageout daemon settings.
*/
static void
vm_pageout_init(void)
{
/*
* Initialize some paging parameters.
*/
vm_cnt.v_interrupt_free_min = 2;
if (vm_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 (vm_cnt.v_page_count > 1024)
vm_cnt.v_free_min = 4 + (vm_cnt.v_page_count - 1024) / 200;
else
vm_cnt.v_free_min = 4;
vm_cnt.v_pageout_free_min = (2*MAXBSIZE)/PAGE_SIZE +
vm_cnt.v_interrupt_free_min;
vm_cnt.v_free_reserved = vm_pageout_page_count +
vm_cnt.v_pageout_free_min + (vm_cnt.v_page_count / 768);
vm_cnt.v_free_severe = vm_cnt.v_free_min / 2;
vm_cnt.v_free_target = 4 * vm_cnt.v_free_min + vm_cnt.v_free_reserved;
vm_cnt.v_free_min += vm_cnt.v_free_reserved;
vm_cnt.v_free_severe += vm_cnt.v_free_reserved;
vm_cnt.v_inactive_target = (3 * vm_cnt.v_free_target) / 2;
if (vm_cnt.v_inactive_target > vm_cnt.v_free_count / 3)
vm_cnt.v_inactive_target = vm_cnt.v_free_count / 3;
/*
* Set the default wakeup threshold to be 10% above the minimum
* page limit. This keeps the steady state out of shortfall.
*/
vm_pageout_wakeup_thresh = (vm_cnt.v_free_min / 10) * 11;
/*
* Set interval in seconds for active scan. We want to visit each
* page at least once every ten minutes. This is to prevent worst
* case paging behaviors with stale active LRU.
*/
if (vm_pageout_update_period == 0)
vm_pageout_update_period = 600;
/* XXX does not really belong here */
if (vm_page_max_wired == 0)
vm_page_max_wired = vm_cnt.v_free_count / 3;
}
/*
* vm_pageout is the high level pageout daemon.
*/
static void
vm_pageout(void)
{
int error;
#ifdef VM_NUMA_ALLOC
int i;
#endif
swap_pager_swap_init();
#ifdef VM_NUMA_ALLOC
for (i = 1; i < vm_ndomains; i++) {
error = kthread_add(vm_pageout_worker, (void *)(uintptr_t)i,
curproc, NULL, 0, 0, "dom%d", i);
if (error != 0) {
panic("starting pageout for domain %d, error %d\n",
i, error);
}
}
#endif
error = kthread_add(uma_reclaim_worker, NULL, curproc, NULL,
0, 0, "uma");
if (error != 0)
panic("starting uma_reclaim helper, error %d\n", error);
vm_pageout_worker((void *)(uintptr_t)0);
}
/*
* Unless the free page queue lock is held by the caller, this function
* should be regarded as advisory. Specifically, the caller should
* not msleep() on &vm_cnt.v_free_count following this function unless
* the free page queue lock is held until the msleep() is performed.
*/
void
pagedaemon_wakeup(void)
{
if (!vm_pageout_wanted && curthread->td_proc != pageproc) {
vm_pageout_wanted = true;
wakeup(&vm_pageout_wanted);
}
}
#if !defined(NO_SWAPPING)
static void
vm_req_vmdaemon(int req)
{
static int lastrun = 0;
mtx_lock(&vm_daemon_mtx);
vm_pageout_req_swapout |= req;
if ((ticks > (lastrun + hz)) || (ticks < lastrun)) {
wakeup(&vm_daemon_needed);
lastrun = ticks;
}
mtx_unlock(&vm_daemon_mtx);
}
static void
vm_daemon(void)
{
struct rlimit rsslim;
struct proc *p;
struct thread *td;
struct vmspace *vm;
int breakout, swapout_flags, tryagain, attempts;
#ifdef RACCT
uint64_t rsize, ravailable;
#endif
while (TRUE) {
mtx_lock(&vm_daemon_mtx);
msleep(&vm_daemon_needed, &vm_daemon_mtx, PPAUSE, "psleep",
#ifdef RACCT
racct_enable ? hz : 0
#else
0
#endif
);
swapout_flags = vm_pageout_req_swapout;
vm_pageout_req_swapout = 0;
mtx_unlock(&vm_daemon_mtx);
if (swapout_flags)
swapout_procs(swapout_flags);
/*
* scan the processes for exceeding their rlimits or if
* process is swapped out -- deactivate pages
*/
tryagain = 0;
attempts = 0;
again:
attempts++;
sx_slock(&allproc_lock);
FOREACH_PROC_IN_SYSTEM(p) {
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_state != PRS_NORMAL ||
p->p_flag & (P_INEXEC | P_SYSTEM | P_WEXIT)) {
PROC_UNLOCK(p);
continue;
}
/*
* if the process is in a non-running type state,
* don't touch it.
*/
breakout = 0;
FOREACH_THREAD_IN_PROC(p, td) {
thread_lock(td);
if (!TD_ON_RUNQ(td) &&
!TD_IS_RUNNING(td) &&
!TD_IS_SLEEPING(td) &&
!TD_IS_SUSPENDED(td)) {
thread_unlock(td);
breakout = 1;
break;
}
thread_unlock(td);
}
if (breakout) {
PROC_UNLOCK(p);
continue;
}
/*
* get a limit
*/
lim_rlimit_proc(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_flag & P_INMEM) == 0)
limit = 0; /* XXX */
vm = vmspace_acquire_ref(p);
_PHOLD_LITE(p);
PROC_UNLOCK(p);
if (vm == NULL) {
PRELE(p);
continue;
}
sx_sunlock(&allproc_lock);
size = vmspace_resident_count(vm);
if (size >= limit) {
vm_pageout_map_deactivate_pages(
&vm->vm_map, limit);
}
#ifdef RACCT
if (racct_enable) {
rsize = IDX_TO_OFF(size);
PROC_LOCK(p);
racct_set(p, RACCT_RSS, rsize);
ravailable = racct_get_available(p, RACCT_RSS);
PROC_UNLOCK(p);
if (rsize > ravailable) {
/*
* Don't be overly aggressive; this
* might be an innocent process,
* and the limit could've been exceeded
* by some memory hog. Don't try
* to deactivate more than 1/4th
* of process' resident set size.
*/
if (attempts <= 8) {
if (ravailable < rsize -
(rsize / 4)) {
ravailable = rsize -
(rsize / 4);
}
}
vm_pageout_map_deactivate_pages(
&vm->vm_map,
OFF_TO_IDX(ravailable));
/* Update RSS usage after paging out. */
size = vmspace_resident_count(vm);
rsize = IDX_TO_OFF(size);
PROC_LOCK(p);
racct_set(p, RACCT_RSS, rsize);
PROC_UNLOCK(p);
if (rsize > ravailable)
tryagain = 1;
}
}
#endif
vmspace_free(vm);
sx_slock(&allproc_lock);
PRELE(p);
}
sx_sunlock(&allproc_lock);
if (tryagain != 0 && attempts <= 10)
goto again;
}
}
#endif /* !defined(NO_SWAPPING) */
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