d/freebsd-skq
1
0
Fork 0
Code Issues Pull Requests Packages Projects Releases Wiki Activity
41c66e4188
freebsd-skq/sys/vm/vm_pageout.c
mckusick 9d4f0d78fa The buffer queue mechanism has been reformulated. Instead of having 
QUEUE_AGE, QUEUE_LRU, and QUEUE_EMPTY we instead have QUEUE_CLEAN,
QUEUE_DIRTY, QUEUE_EMPTY, and QUEUE_EMPTYKVA.  With this patch clean
and dirty buffers have been separated.  Empty buffers with KVM
assignments have been separated from truely empty buffers.  getnewbuf()
has been rewritten and now operates in a 100% optimal fashion.  That is,
it is able to find precisely the right kind of buffer it needs to
allocate a new buffer, defragment KVM, or to free-up an existing buffer
when the buffer cache is full (which is a steady-state situation for
the buffer cache).

Buffer flushing has been reorganized.  Previously buffers were flushed
in the context of whatever process hit the conditions forcing buffer
flushing to occur.  This resulted in processes blocking on conditions
unrelated to what they were doing.  This also resulted in inappropriate
VFS stacking chains due to multiple processes getting stuck trying to
flush dirty buffers or due to a single process getting into a situation
where it might attempt to flush buffers recursively - a situation that
was only partially fixed in prior commits.  We have added a new daemon
called the buf_daemon which is responsible for flushing dirty buffers
when the number of dirty buffers exceeds the vfs.hidirtybuffers limit.
This daemon attempts to dynamically adjust the rate at which dirty buffers
are flushed such that getnewbuf() calls (almost) never block.

The number of nbufs and amount of buffer space is now scaled past the
8MB limit that was previously imposed for systems with over 64MB of
memory, and the vfs.{lo,hi}dirtybuffers limits have been relaxed
somewhat.  The number of physical buffers has been increased with the
intention that we will manage physical I/O differently in the future.

reassignbuf previously attempted to keep the dirtyblkhd list sorted which
could result in non-deterministic operation under certain conditions,
such as when a large number of dirty buffers are being managed.  This
algorithm has been changed.  reassignbuf now keeps buffers locally sorted
if it can do so cheaply, and otherwise gives up and adds buffers to
the head of the dirtyblkhd list.  The new algorithm is deterministic but
not perfect.  The new algorithm greatly reduces problems that previously
occured when write_behind was turned off in the system.

The P_FLSINPROG proc->p_flag bit has been replaced by the more descriptive
P_BUFEXHAUST bit.  This bit allows processes working with filesystem
buffers to use available emergency reserves.  Normal processes do not set
this bit and are not allowed to dig into emergency reserves.  The purpose
of this bit is to avoid low-memory deadlocks.

A small race condition was fixed in getpbuf() in vm/vm_pager.c.

Submitted by:	Matthew Dillon <dillon@apollo.backplane.com>
Reviewed by:	Kirk McKusick <mckusick@mckusick.com>
1999-07-04 00:25:38 +00:00

1460 lines
38 KiB
C
Raw Blame History

/*
* 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.
*
* $Id: vm_pageout.c,v 1.143 1999/07/01 13:21:46 peter Exp $
*/
/*
* The proverbial page-out daemon.
*/
#include "opt_vm.h"
#include <sys/param.h>
#include <sys/systm.h>
#include <sys/kernel.h>
#include <sys/proc.h>
#include <sys/kthread.h>
#include <sys/resourcevar.h>
#include <sys/signalvar.h>
#include <sys/vnode.h>
#include <sys/vmmeter.h>
#include <sys/sysctl.h>
#include <vm/vm.h>
#include <vm/vm_param.h>
#include <vm/vm_prot.h>
#include <sys/lock.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>
/*
* System initialization
*/
/* the kernel process "vm_pageout"*/
static void vm_pageout __P((void));
static int vm_pageout_clean __P((vm_page_t));
static int vm_pageout_scan __P((void));
static int vm_pageout_free_page_calc __P((vm_size_t count));
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 __P((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=0; /* Event on which pageout daemon sleeps */
int vm_pageout_deficit=0; /* Estimated number of pages deficit */
int vm_pageout_pages_needed=0; /* flag saying that the pageout daemon needs pages */
extern int npendingio;
#if !defined(NO_SWAPPING)
static int vm_pageout_req_swapout; /* XXX */
static int vm_daemon_needed;
#endif
extern int nswiodone;
extern int vm_swap_size;
static int vm_pageout_stats_max=0, vm_pageout_stats_interval = 0;
static int vm_pageout_full_stats_interval = 0;
static int vm_pageout_stats_free_max=0, vm_pageout_algorithm_lru=0;
static int defer_swap_pageouts=0;
static int disable_swap_pageouts=0;
static int max_page_launder=100;
#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_lru, 0, "LRU page mgmt");
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");
SYSCTL_INT(_vm, OID_AUTO, pageout_stats_free_max,
CTLFLAG_RW, &vm_pageout_stats_free_max, 0, "Not implemented");
#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");
SYSCTL_INT(_vm, OID_AUTO, max_page_launder,
CTLFLAG_RW, &max_page_launder, 0, "Maximum number of pages to clean per pass");
#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)
typedef void freeer_fcn_t __P((vm_map_t, vm_object_t, vm_pindex_t, int));
static void vm_pageout_map_deactivate_pages __P((vm_map_t, vm_pindex_t));
static freeer_fcn_t vm_pageout_object_deactivate_pages;
static void vm_req_vmdaemon __P((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;
{
register vm_object_t object;
vm_page_t mc[2*vm_pageout_page_count];
int pageout_count;
int i, forward_okay, backward_okay, page_base;
vm_pindex_t pindex = m->pindex;
object = m->object;
/*
* 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.
*/
#if 0
/*
* If not OBJT_SWAP, additional memory may be needed to do the pageout.
* Try to avoid the deadlock.
*/
if ((object->type == OBJT_DEFAULT) &&
((cnt.v_free_count + cnt.v_cache_count) < cnt.v_pageout_free_min))
return 0;
#endif
/*
* Don't mess with the page if it's busy.
*/
if ((m->hold_count != 0) ||
((m->busy != 0) || (m->flags & PG_BUSY)))
return 0;
#if 0
/*
* XXX REMOVED XXX. vm_object_collapse() can block, which can
* change the page state. Calling vm_object_collapse() might also
* destroy or rename the page because we have not busied it yet!!!
* So this code segment is removed.
*/
/*
* Try collapsing before it's too late. XXX huh? Why are we doing
* this here?
*/
if (object->backing_object) {
vm_object_collapse(object);
}
#endif
mc[vm_pageout_page_count] = m;
pageout_count = 1;
page_base = vm_pageout_page_count;
forward_okay = TRUE;
if (pindex != 0)
backward_okay = TRUE;
else
backward_okay = FALSE;
/*
* 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.
*/
for (i = 1; (i < vm_pageout_page_count) && (forward_okay || backward_okay); i++) {
vm_page_t p;
/*
* See if forward page is clusterable.
*/
if (forward_okay) {
/*
* Stop forward scan at end of object.
*/
if ((pindex + i) > object->size) {
forward_okay = FALSE;
goto do_backward;
}
p = vm_page_lookup(object, pindex + i);
if (p) {
if (((p->queue - p->pc) == PQ_CACHE) ||
(p->flags & PG_BUSY) || p->busy) {
forward_okay = FALSE;
goto do_backward;
}
vm_page_test_dirty(p);
if ((p->dirty & p->valid) != 0 &&
(p->queue == PQ_INACTIVE) &&
(p->wire_count == 0) &&
(p->hold_count == 0)) {
mc[vm_pageout_page_count + i] = p;
pageout_count++;
if (pageout_count == vm_pageout_page_count)
break;
} else {
forward_okay = FALSE;
}
} else {
forward_okay = FALSE;
}
}
do_backward:
/*
* See if backward page is clusterable.
*/
if (backward_okay) {
/*
* Stop backward scan at beginning of object.
*/
if ((pindex - i) == 0) {
backward_okay = FALSE;
}
p = vm_page_lookup(object, pindex - i);
if (p) {
if (((p->queue - p->pc) == PQ_CACHE) ||
(p->flags & PG_BUSY) || p->busy) {
backward_okay = FALSE;
continue;
}
vm_page_test_dirty(p);
if ((p->dirty & p->valid) != 0 &&
(p->queue == PQ_INACTIVE) &&
(p->wire_count == 0) &&
(p->hold_count == 0)) {
mc[vm_pageout_page_count - i] = p;
pageout_count++;
page_base--;
if (pageout_count == vm_pageout_page_count)
break;
} else {
backward_okay = FALSE;
}
} else {
backward_okay = FALSE;
}
}
}
/*
* 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(mc, count, flags)
vm_page_t *mc;
int count;
int flags;
{
register vm_object_t object;
int pageout_status[count];
int numpagedout = 0;
int i;
/*
* 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.
*/
for (i = 0; i < count; i++) {
vm_page_io_start(mc[i]);
vm_page_protect(mc[i], VM_PROT_READ);
}
object = mc[0]->object;
vm_object_pip_add(object, count);
vm_pager_put_pages(object, mc, count,
(flags | ((object == kernel_object) ? OBJPC_SYNC : 0)),
pageout_status);
for (i = 0; i < count; i++) {
vm_page_t mt = mc[i];
switch (pageout_status[i]) {
case VM_PAGER_OK:
numpagedout++;
break;
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(VM_PAGE_TO_PHYS(mt));
mt->dirty = 0;
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);
}
}
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(map, object, desired, map_remove_only)
vm_map_t map;
vm_object_t object;
vm_pindex_t desired;
int map_remove_only;
{
register vm_page_t p, next;
int rcount;
int remove_mode;
int s;
if (object->type == OBJT_DEVICE)
return;
while (object) {
if (pmap_resident_count(vm_map_pmap(map)) <= desired)
return;
if (object->paging_in_progress)
return;
remove_mode = map_remove_only;
if (object->shadow_count > 1)
remove_mode = 1;
/*
* scan the objects entire memory queue
*/
rcount = object->resident_page_count;
p = TAILQ_FIRST(&object->memq);
while (p && (rcount-- > 0)) {
int actcount;
if (pmap_resident_count(vm_map_pmap(map)) <= desired)
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) ||
!pmap_page_exists(vm_map_pmap(map), VM_PAGE_TO_PHYS(p))) {
p = next;
continue;
}
actcount = pmap_ts_referenced(VM_PAGE_TO_PHYS(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_lru || (p->act_count == 0))) {
vm_page_protect(p, VM_PROT_NONE);
vm_page_deactivate(p);
} else {
s = splvm();
TAILQ_REMOVE(&vm_page_queue_active, p, pageq);
TAILQ_INSERT_TAIL(&vm_page_queue_active, p, pageq);
splx(s);
}
} 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;
s = splvm();
TAILQ_REMOVE(&vm_page_queue_active, p, pageq);
TAILQ_INSERT_TAIL(&vm_page_queue_active, p, pageq);
splx(s);
}
} else if (p->queue == PQ_INACTIVE) {
vm_page_protect(p, VM_PROT_NONE);
}
p = next;
}
object = object->backing_object;
}
return;
}
/*
* 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;
vm_pindex_t desired;
{
vm_map_entry_t tmpe;
vm_object_t obj, bigobj;
if (lockmgr(&map->lock, LK_EXCLUSIVE | LK_NOWAIT, (void *)0, curproc)) {
return;
}
bigobj = NULL;
/*
* 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) && (obj->shadow_count <= 1) &&
((bigobj == NULL) ||
(bigobj->resident_page_count < obj->resident_page_count))) {
bigobj = obj;
}
}
tmpe = tmpe->next;
}
if (bigobj)
vm_pageout_object_deactivate_pages(map, bigobj, desired, 0);
/*
* 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)
vm_pageout_object_deactivate_pages(map, obj, desired, 0);
}
tmpe = tmpe->next;
};
/*
* Remove all mappings if a process is swapped out, this will free page
* table pages.
*/
if (desired == 0)
pmap_remove(vm_map_pmap(map),
VM_MIN_ADDRESS, VM_MAXUSER_ADDRESS);
vm_map_unlock(map);
return;
}
#endif
/*
* Don't try to be fancy - being fancy can lead to VOP_LOCK's and therefore
* to vnode deadlocks. We only do it for OBJT_DEFAULT and OBJT_SWAP objects
* which we know can be trivially freed.
*/
void
vm_pageout_page_free(vm_page_t m) {
vm_object_t object = m->object;
int type = object->type;
if (type == OBJT_SWAP || type == OBJT_DEFAULT)
vm_object_reference(object);
vm_page_busy(m);
vm_page_protect(m, VM_PROT_NONE);
vm_page_free(m);
if (type == OBJT_SWAP || type == OBJT_DEFAULT)
vm_object_deallocate(object);
}
/*
* vm_pageout_scan does the dirty work for the pageout daemon.
*/
static int
vm_pageout_scan()
{
vm_page_t m, next;
int page_shortage, maxscan, pcount;
int addl_page_shortage, addl_page_shortage_init;
int maxlaunder;
int launder_loop = 0;
struct proc *p, *bigproc;
vm_offset_t size, bigsize;
vm_object_t object;
int force_wakeup = 0;
int actcount;
int vnodes_skipped = 0;
int s;
/*
* Do whatever cleanup that the pmap code can.
*/
pmap_collect();
addl_page_shortage_init = vm_pageout_deficit;
vm_pageout_deficit = 0;
if (max_page_launder == 0)
max_page_launder = 1;
/*
* Calculate the number of pages we want to either free or move
* to the cache.
*/
page_shortage = (cnt.v_free_target + cnt.v_cache_min) -
(cnt.v_free_count + cnt.v_cache_count);
page_shortage += addl_page_shortage_init;
/*
* Figure out what to do with dirty pages when they are encountered.
* Assume that 1/3 of the pages on the inactive list are clean. If
* we think we can reach our target, disable laundering (do not
* clean any dirty pages). If we miss the target we will loop back
* up and do a laundering run.
*/
if (cnt.v_inactive_count / 3 > page_shortage) {
maxlaunder = 0;
launder_loop = 0;
} else {
maxlaunder =
(cnt.v_inactive_target > max_page_launder) ?
max_page_launder : cnt.v_inactive_target;
launder_loop = 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.
*/
rescan0:
addl_page_shortage = addl_page_shortage_init;
maxscan = cnt.v_inactive_count;
for (m = TAILQ_FIRST(&vm_page_queue_inactive);
m != NULL && maxscan-- > 0 && page_shortage > 0;
m = next) {
cnt.v_pdpages++;
if (m->queue != PQ_INACTIVE) {
goto rescan0;
}
next = TAILQ_NEXT(m, pageq);
if (m->hold_count) {
s = splvm();
TAILQ_REMOVE(&vm_page_queue_inactive, m, pageq);
TAILQ_INSERT_TAIL(&vm_page_queue_inactive, m, pageq);
splx(s);
addl_page_shortage++;
continue;
}
/*
* Dont 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(VM_PAGE_TO_PHYS(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(VM_PAGE_TO_PHYS(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(VM_PAGE_TO_PHYS(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) {
vm_page_test_dirty(m);
} else {
vm_page_dirty(m);
}
/*
* Invalid pages can be easily freed
*/
if (m->valid == 0) {
vm_pageout_page_free(m);
cnt.v_dfree++;
--page_shortage;
/*
* Clean pages can be placed onto the cache queue.
*/
} else if (m->dirty == 0) {
vm_page_cache(m);
--page_shortage;
/*
* Dirty pages need to be paged out. Note that we clean
* only a limited number of pages per pagedaemon pass.
*/
} else if (maxlaunder > 0) {
int written;
int swap_pageouts_ok;
struct vnode *vp = NULL;
object = m->object;
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 &&
(cnt.v_free_count + cnt.v_cache_count) < cnt.v_free_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)) {
s = splvm();
TAILQ_REMOVE(&vm_page_queue_inactive, m, pageq);
TAILQ_INSERT_TAIL(&vm_page_queue_inactive, m, pageq);
splx(s);
continue;
}
/*
* For now we protect against potential memory
* deadlocks by requiring significant memory to be
* free if the object is not OBJT_DEFAULT or OBJT_SWAP.
* We do not 'trust' any other object type to operate
* with low memory, not even OBJT_DEVICE. The VM
* allocator will special case allocations done by
* the pageout daemon so the check below actually
* does have some hysteresis in it. It isn't the best
* solution, though.
*/
if (object->type != OBJT_DEFAULT &&
object->type != OBJT_SWAP &&
cnt.v_free_count < cnt.v_free_reserved) {
s = splvm();
TAILQ_REMOVE(&vm_page_queue_inactive, m, pageq);
TAILQ_INSERT_TAIL(&vm_page_queue_inactive, m,
pageq);
splx(s);
continue;
}
/*
* Presumably we have sufficient free memory to do
* the more sophisticated checks and locking required
* for vnodes.
*
* The object is already known NOT to be dead. The
* vget() may still block, though, because
* VOP_ISLOCKED() doesn't check to see if an inode
* (v_data) is associated with the vnode. If it isn't,
* vget() will load in it from disk. Worse, vget()
* may actually get stuck waiting on "inode" if another
* process is in the process of bringing the inode in.
* This is bad news for us either way.
*
* So for the moment we check v_data == NULL as a
* workaround. This means that vnodes which do not
* use v_data in the way we expect probably will not
* wind up being paged out by the pager and it will be
* up to the syncer to get them. That's better then
* us blocking here.
*
* This whole code section is bogus - we need to fix
* the vnode pager to handle vm_page_t's without us
* having to do any sophisticated VOP tests.
*/
if (object->type == OBJT_VNODE) {
vp = object->handle;
if (VOP_ISLOCKED(vp) ||
vp->v_data == NULL ||
vget(vp, LK_EXCLUSIVE|LK_NOOBJ, curproc)) {
if ((m->queue == PQ_INACTIVE) &&
(m->hold_count == 0) &&
(m->busy == 0) &&
(m->flags & PG_BUSY) == 0) {
s = splvm();
TAILQ_REMOVE(&vm_page_queue_inactive, m, pageq);
TAILQ_INSERT_TAIL(&vm_page_queue_inactive, m, pageq);
splx(s);
}
if (object->flags & OBJ_MIGHTBEDIRTY)
vnodes_skipped++;
continue;
}
/*
* The page might have been moved to another queue
* during potential blocking in vget() above.
*/
if (m->queue != PQ_INACTIVE) {
if (object->flags & OBJ_MIGHTBEDIRTY)
vnodes_skipped++;
vput(vp);
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)) {
vput(vp);
continue;
}
/*
* If the page has become held, then skip it
*/
if (m->hold_count) {
s = splvm();
TAILQ_REMOVE(&vm_page_queue_inactive, m, pageq);
TAILQ_INSERT_TAIL(&vm_page_queue_inactive, m, pageq);
splx(s);
if (object->flags & OBJ_MIGHTBEDIRTY)
vnodes_skipped++;
vput(vp);
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.
*/
written = vm_pageout_clean(m);
if (vp)
vput(vp);
maxlaunder -= written;
}
}
/*
* If we still have a page shortage and we didn't launder anything,
* run the inactive scan again and launder something this time.
*/
if (launder_loop == 0 && page_shortage > 0) {
launder_loop = 1;
maxlaunder =
(cnt.v_inactive_target > max_page_launder) ?
max_page_launder : cnt.v_inactive_target;
goto rescan0;
}
/*
* Compute the page shortage from the point of view of having to
* move pages from the active queue to the inactive queue.
*/
page_shortage = (cnt.v_inactive_target + cnt.v_cache_min) -
(cnt.v_free_count + cnt.v_inactive_count + cnt.v_cache_count);
page_shortage += addl_page_shortage;
/*
* Scan the active queue for things we can deactivate
*/
pcount = cnt.v_active_count;
m = TAILQ_FIRST(&vm_page_queue_active);
while ((m != NULL) && (pcount-- > 0) && (page_shortage > 0)) {
/*
* This is a consistancy check, and should likely be a panic
* or warning.
*/
if (m->queue != PQ_ACTIVE) {
break;
}
next = TAILQ_NEXT(m, pageq);
/*
* Don't deactivate pages that are busy.
*/
if ((m->busy != 0) ||
(m->flags & PG_BUSY) ||
(m->hold_count != 0)) {
s = splvm();
TAILQ_REMOVE(&vm_page_queue_active, m, pageq);
TAILQ_INSERT_TAIL(&vm_page_queue_active, m, pageq);
splx(s);
m = next;
continue;
}
/*
* The count for pagedaemon pages is done after checking the
* page for eligbility...
*/
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(VM_PAGE_TO_PHYS(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)) {
s = splvm();
TAILQ_REMOVE(&vm_page_queue_active, m, pageq);
TAILQ_INSERT_TAIL(&vm_page_queue_active, m, pageq);
splx(s);
} else {
m->act_count -= min(m->act_count, ACT_DECLINE);
if (vm_pageout_algorithm_lru ||
(m->object->ref_count == 0) || (m->act_count == 0)) {
page_shortage--;
if (m->object->ref_count == 0) {
vm_page_protect(m, VM_PROT_NONE);
if (m->dirty == 0)
vm_page_cache(m);
else
vm_page_deactivate(m);
} else {
vm_page_deactivate(m);
}
} else {
s = splvm();
TAILQ_REMOVE(&vm_page_queue_active, m, pageq);
TAILQ_INSERT_TAIL(&vm_page_queue_active, m, pageq);
splx(s);
}
}
m = next;
}
s = splvm();
/*
* 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;
m = vm_page_list_find(PQ_CACHE, cache_rover, FALSE);
if (!m)
break;
if ((m->flags & PG_BUSY) || m->busy || m->hold_count || m->wire_count) {
#ifdef INVARIANTS
printf("Warning: busy page %p found in cache\n", m);
#endif
vm_page_deactivate(m);
continue;
}
cache_rover = (cache_rover + PQ_PRIME2) & PQ_L2_MASK;
vm_pageout_page_free(m);
cnt.v_dfree++;
}
splx(s);
#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 ((cnt.v_cache_count + cnt.v_free_count) <
(cnt.v_free_target + cnt.v_cache_min) ) {
if (vnodes_skipped &&
(cnt.v_cache_count + cnt.v_free_count) < cnt.v_free_min) {
(void) speedup_syncer();
}
#if !defined(NO_SWAPPING)
if (vm_swap_enabled &&
(cnt.v_free_count + cnt.v_cache_count < cnt.v_free_target)) {
vm_req_vmdaemon();
vm_pageout_req_swapout |= VM_SWAP_NORMAL;
}
#endif
}
/*
* make sure that we have swap space -- if we are low on memory and
* swap -- then kill the biggest process.
*/
if ((vm_swap_size == 0 || swap_pager_full) &&
((cnt.v_free_count + cnt.v_cache_count) < cnt.v_free_min)) {
bigproc = NULL;
bigsize = 0;
for (p = allproc.lh_first; p != 0; p = p->p_list.le_next) {
/*
* if this is a system process, skip it
*/
if ((p->p_flag & P_SYSTEM) || (p->p_lock > 0) ||
(p->p_pid == 1) ||
((p->p_pid < 48) && (vm_swap_size != 0))) {
continue;
}
/*
* if the process is in a non-running type state,
* don't touch it.
*/
if (p->p_stat != SRUN && p->p_stat != SSLEEP) {
continue;
}
/*
* get the process size
*/
size = vmspace_resident_count(p->p_vmspace);
/*
* if the this process is bigger than the biggest one
* remember it.
*/
if (size > bigsize) {
bigproc = p;
bigsize = size;
}
}
if (bigproc != NULL) {
killproc(bigproc, "out of swap space");
bigproc->p_estcpu = 0;
bigproc->p_nice = PRIO_MIN;
resetpriority(bigproc);
wakeup(&cnt.v_free_count);
}
}
return force_wakeup;
}
/*
* 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 accumlation still occurs. This code
* helps the situation where paging just starts to occur.
*/
static void
vm_pageout_page_stats()
{
int s;
vm_page_t m,next;
int pcount,tpcount; /* Number of pages to check */
static int fullintervalcount = 0;
int page_shortage;
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;
}
m = TAILQ_FIRST(&vm_page_queue_active);
while ((m != NULL) && (pcount-- > 0)) {
int actcount;
if (m->queue != PQ_ACTIVE) {
break;
}
next = TAILQ_NEXT(m, pageq);
/*
* Don't deactivate pages that are busy.
*/
if ((m->busy != 0) ||
(m->flags & PG_BUSY) ||
(m->hold_count != 0)) {
s = splvm();
TAILQ_REMOVE(&vm_page_queue_active, m, pageq);
TAILQ_INSERT_TAIL(&vm_page_queue_active, m, pageq);
splx(s);
m = next;
continue;
}
actcount = 0;
if (m->flags & PG_REFERENCED) {
vm_page_flag_clear(m, PG_REFERENCED);
actcount += 1;
}
actcount += pmap_ts_referenced(VM_PAGE_TO_PHYS(m));
if (actcount) {
m->act_count += ACT_ADVANCE + actcount;
if (m->act_count > ACT_MAX)
m->act_count = ACT_MAX;
s = splvm();
TAILQ_REMOVE(&vm_page_queue_active, m, pageq);
TAILQ_INSERT_TAIL(&vm_page_queue_active, m, pageq);
splx(s);
} 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.
*/
vm_page_protect(m, VM_PROT_NONE);
vm_page_deactivate(m);
} else {
m->act_count -= min(m->act_count, ACT_DECLINE);
s = splvm();
TAILQ_REMOVE(&vm_page_queue_active, m, pageq);
TAILQ_INSERT_TAIL(&vm_page_queue_active, m, pageq);
splx(s);
}
}
m = next;
}
}
static int
vm_pageout_free_page_calc(count)
vm_size_t count;
{
if (count < cnt.v_page_count)
return 0;
/*
* 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 + (count / 768) + PQ_L2_SIZE;
cnt.v_free_min += cnt.v_free_reserved;
return 1;
}
/*
* vm_pageout is the high level pageout daemon.
*/
static void
vm_pageout()
{
/*
* Initialize some paging parameters.
*/
cnt.v_interrupt_free_min = 2;
if (cnt.v_page_count < 2000)
vm_pageout_page_count = 8;
vm_pageout_free_page_calc(cnt.v_page_count);
/*
* free_reserved needs to include enough for the largest swap pager
* structures plus enough for any pv_entry structs when paging.
*/
if (cnt.v_free_count > 6144)
cnt.v_free_target = 3 * 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;
/*
* Set maximum free per pass
*/
if (vm_pageout_stats_free_max == 0)
vm_pageout_stats_free_max = 5;
max_page_launder = (cnt.v_page_count > 1800 ? 32 : 16);
curproc->p_flag |= P_BUFEXHAUST;
swap_pager_swap_init();
/*
* The pageout daemon is never done, so loop forever.
*/
while (TRUE) {
int error;
int s = splvm();
if (!vm_pages_needed ||
((cnt.v_free_count + cnt.v_cache_count) > cnt.v_free_min)) {
vm_pages_needed = 0;
error = tsleep(&vm_pages_needed,
PVM, "psleep", vm_pageout_stats_interval * hz);
if (error && !vm_pages_needed) {
splx(s);
vm_pageout_page_stats();
continue;
}
} else if (vm_pages_needed) {
vm_pages_needed = 0;
tsleep(&vm_pages_needed, PVM, "psleep", hz/2);
}
if (vm_pages_needed)
cnt.v_pdwakeups++;
vm_pages_needed = 0;
splx(s);
vm_pageout_scan();
vm_pageout_deficit = 0;
wakeup(&cnt.v_free_count);
}
}
void
pagedaemon_wakeup()
{
if (!vm_pages_needed && curproc != pageproc) {
vm_pages_needed++;
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 proc *p;
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
*/
for (p = allproc.lh_first; p != 0; p = p->p_list.le_next) {
vm_pindex_t limit, size;
/*
* if this is a system process or if we have already
* looked at this process, skip it.
*/
if (p->p_flag & (P_SYSTEM | P_WEXIT)) {
continue;
}
/*
* if the process is in a non-running type state,
* don't touch it.
*/
if (p->p_stat != SRUN && p->p_stat != SSLEEP) {
continue;
}
/*
* get a limit
*/
limit = OFF_TO_IDX(
qmin(p->p_rlimit[RLIMIT_RSS].rlim_cur,
p->p_rlimit[RLIMIT_RSS].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 */
size = vmspace_resident_count(p->p_vmspace);
if (limit >= 0 && size >= limit) {
vm_pageout_map_deactivate_pages(
&p->p_vmspace->vm_map, limit);
}
}
}
}
#endif
Reference in New Issue View Git Blame Copy Permalink