NetBSD/sys/uvm/uvm_pdaemon.c

961 lines
22 KiB
C

/* $NetBSD: uvm_pdaemon.c,v 1.84 2007/02/22 06:05:01 thorpej Exp $ */
/*
* Copyright (c) 1997 Charles D. Cranor and Washington University.
* Copyright (c) 1991, 1993, The Regents of the University of California.
*
* All rights reserved.
*
* This code is derived from software contributed to Berkeley by
* The Mach Operating System project at Carnegie-Mellon University.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 3. All advertising materials mentioning features or use of this software
* must display the following acknowledgement:
* This product includes software developed by Charles D. Cranor,
* Washington University, the University of California, Berkeley and
* its contributors.
* 4. Neither the name of the University nor the names of its contributors
* may be used to endorse or promote products derived from this software
* without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*
* @(#)vm_pageout.c 8.5 (Berkeley) 2/14/94
* from: Id: uvm_pdaemon.c,v 1.1.2.32 1998/02/06 05:26:30 chs Exp
*
*
* Copyright (c) 1987, 1990 Carnegie-Mellon University.
* All rights reserved.
*
* Permission to use, copy, modify and distribute this software and
* its documentation is hereby granted, provided that both the copyright
* notice and this permission notice appear in all copies of the
* software, derivative works or modified versions, and any portions
* thereof, and that both notices appear in supporting documentation.
*
* CARNEGIE MELLON ALLOWS FREE USE OF THIS SOFTWARE IN ITS "AS IS"
* CONDITION. CARNEGIE MELLON DISCLAIMS ANY LIABILITY OF ANY KIND
* FOR ANY DAMAGES WHATSOEVER RESULTING FROM THE USE OF THIS SOFTWARE.
*
* Carnegie Mellon requests users of this software to return to
*
* Software Distribution Coordinator or Software.Distribution@CS.CMU.EDU
* School of Computer Science
* Carnegie Mellon University
* Pittsburgh PA 15213-3890
*
* any improvements or extensions that they make and grant Carnegie the
* rights to redistribute these changes.
*/
/*
* uvm_pdaemon.c: the page daemon
*/
#include <sys/cdefs.h>
__KERNEL_RCSID(0, "$NetBSD: uvm_pdaemon.c,v 1.84 2007/02/22 06:05:01 thorpej Exp $");
#include "opt_uvmhist.h"
#include "opt_readahead.h"
#include <sys/param.h>
#include <sys/proc.h>
#include <sys/systm.h>
#include <sys/kernel.h>
#include <sys/pool.h>
#include <sys/buf.h>
#include <uvm/uvm.h>
#include <uvm/uvm_pdpolicy.h>
/*
* UVMPD_NUMDIRTYREACTS is how many dirty pages the pagedaemon will reactivate
* in a pass thru the inactive list when swap is full. the value should be
* "small"... if it's too large we'll cycle the active pages thru the inactive
* queue too quickly to for them to be referenced and avoid being freed.
*/
#define UVMPD_NUMDIRTYREACTS 16
/*
* local prototypes
*/
static void uvmpd_scan(void);
static void uvmpd_scan_queue(void);
static void uvmpd_tune(void);
/*
* XXX hack to avoid hangs when large processes fork.
*/
int uvm_extrapages;
/*
* uvm_wait: wait (sleep) for the page daemon to free some pages
*
* => should be called with all locks released
* => should _not_ be called by the page daemon (to avoid deadlock)
*/
void
uvm_wait(const char *wmsg)
{
int timo = 0;
int s = splbio();
/*
* check for page daemon going to sleep (waiting for itself)
*/
if (curproc == uvm.pagedaemon_proc && uvmexp.paging == 0) {
/*
* now we have a problem: the pagedaemon wants to go to
* sleep until it frees more memory. but how can it
* free more memory if it is asleep? that is a deadlock.
* we have two options:
* [1] panic now
* [2] put a timeout on the sleep, thus causing the
* pagedaemon to only pause (rather than sleep forever)
*
* note that option [2] will only help us if we get lucky
* and some other process on the system breaks the deadlock
* by exiting or freeing memory (thus allowing the pagedaemon
* to continue). for now we panic if DEBUG is defined,
* otherwise we hope for the best with option [2] (better
* yet, this should never happen in the first place!).
*/
printf("pagedaemon: deadlock detected!\n");
timo = hz >> 3; /* set timeout */
#if defined(DEBUG)
/* DEBUG: panic so we can debug it */
panic("pagedaemon deadlock");
#endif
}
simple_lock(&uvm.pagedaemon_lock);
wakeup(&uvm.pagedaemon); /* wake the daemon! */
UVM_UNLOCK_AND_WAIT(&uvmexp.free, &uvm.pagedaemon_lock, false, wmsg,
timo);
splx(s);
}
/*
* uvm_kick_pdaemon: perform checks to determine if we need to
* give the pagedaemon a nudge, and do so if necessary.
*/
void
uvm_kick_pdaemon(void)
{
if (uvmexp.free + uvmexp.paging < uvmexp.freemin ||
(uvmexp.free + uvmexp.paging < uvmexp.freetarg &&
uvmpdpol_needsscan_p())) {
wakeup(&uvm.pagedaemon);
}
}
/*
* uvmpd_tune: tune paging parameters
*
* => called when ever memory is added (or removed?) to the system
* => caller must call with page queues locked
*/
static void
uvmpd_tune(void)
{
UVMHIST_FUNC("uvmpd_tune"); UVMHIST_CALLED(pdhist);
uvmexp.freemin = uvmexp.npages / 20;
/* between 16k and 256k */
/* XXX: what are these values good for? */
uvmexp.freemin = MAX(uvmexp.freemin, (16*1024) >> PAGE_SHIFT);
uvmexp.freemin = MIN(uvmexp.freemin, (256*1024) >> PAGE_SHIFT);
/* Make sure there's always a user page free. */
if (uvmexp.freemin < uvmexp.reserve_kernel + 1)
uvmexp.freemin = uvmexp.reserve_kernel + 1;
uvmexp.freetarg = (uvmexp.freemin * 4) / 3;
if (uvmexp.freetarg <= uvmexp.freemin)
uvmexp.freetarg = uvmexp.freemin + 1;
uvmexp.freetarg += uvm_extrapages;
uvm_extrapages = 0;
uvmexp.wiredmax = uvmexp.npages / 3;
UVMHIST_LOG(pdhist, "<- done, freemin=%d, freetarg=%d, wiredmax=%d",
uvmexp.freemin, uvmexp.freetarg, uvmexp.wiredmax, 0);
}
/*
* uvm_pageout: the main loop for the pagedaemon
*/
void
uvm_pageout(void *arg)
{
int bufcnt, npages = 0;
int extrapages = 0;
UVMHIST_FUNC("uvm_pageout"); UVMHIST_CALLED(pdhist);
UVMHIST_LOG(pdhist,"<starting uvm pagedaemon>", 0, 0, 0, 0);
/*
* ensure correct priority and set paging parameters...
*/
uvm.pagedaemon_proc = curproc;
uvm_lock_pageq();
npages = uvmexp.npages;
uvmpd_tune();
uvm_unlock_pageq();
/*
* main loop
*/
for (;;) {
simple_lock(&uvm.pagedaemon_lock);
UVMHIST_LOG(pdhist," <<SLEEPING>>",0,0,0,0);
UVM_UNLOCK_AND_WAIT(&uvm.pagedaemon,
&uvm.pagedaemon_lock, false, "pgdaemon", 0);
uvmexp.pdwoke++;
UVMHIST_LOG(pdhist," <<WOKE UP>>",0,0,0,0);
/*
* now lock page queues and recompute inactive count
*/
uvm_lock_pageq();
if (npages != uvmexp.npages || extrapages != uvm_extrapages) {
npages = uvmexp.npages;
extrapages = uvm_extrapages;
uvmpd_tune();
}
uvmpdpol_tune();
/*
* Estimate a hint. Note that bufmem are returned to
* system only when entire pool page is empty.
*/
bufcnt = uvmexp.freetarg - uvmexp.free;
if (bufcnt < 0)
bufcnt = 0;
UVMHIST_LOG(pdhist," free/ftarg=%d/%d",
uvmexp.free, uvmexp.freetarg, 0,0);
/*
* scan if needed
*/
if (uvmexp.free + uvmexp.paging < uvmexp.freetarg ||
uvmpdpol_needsscan_p()) {
uvmpd_scan();
}
/*
* if there's any free memory to be had,
* wake up any waiters.
*/
if (uvmexp.free > uvmexp.reserve_kernel ||
uvmexp.paging == 0) {
wakeup(&uvmexp.free);
}
/*
* scan done. unlock page queues (the only lock we are holding)
*/
uvm_unlock_pageq();
buf_drain(bufcnt << PAGE_SHIFT);
/*
* drain pool resources now that we're not holding any locks
*/
pool_drain(0);
/*
* free any cached u-areas we don't need
*/
uvm_uarea_drain(true);
}
/*NOTREACHED*/
}
/*
* uvm_aiodone_worker: a workqueue callback for the aiodone daemon.
*/
void
uvm_aiodone_worker(struct work *wk, void *dummy)
{
int s, free;
struct buf *bp = (void *)wk;
KASSERT(&bp->b_work == wk);
/*
* process an i/o that's done.
*/
free = uvmexp.free;
(*bp->b_iodone)(bp);
if (free <= uvmexp.reserve_kernel) {
s = uvm_lock_fpageq();
wakeup(&uvm.pagedaemon);
uvm_unlock_fpageq(s);
} else {
simple_lock(&uvm.pagedaemon_lock);
wakeup(&uvmexp.free);
simple_unlock(&uvm.pagedaemon_lock);
}
}
/*
* uvmpd_trylockowner: trylock the page's owner.
*
* => called with pageq locked.
* => resolve orphaned O->A loaned page.
* => return the locked simplelock on success. otherwise, return NULL.
*/
struct simplelock *
uvmpd_trylockowner(struct vm_page *pg)
{
struct uvm_object *uobj = pg->uobject;
struct simplelock *slock;
UVM_LOCK_ASSERT_PAGEQ();
if (uobj != NULL) {
slock = &uobj->vmobjlock;
} else {
struct vm_anon *anon = pg->uanon;
KASSERT(anon != NULL);
slock = &anon->an_lock;
}
if (!simple_lock_try(slock)) {
return NULL;
}
if (uobj == NULL) {
/*
* set PQ_ANON if it isn't set already.
*/
if ((pg->pqflags & PQ_ANON) == 0) {
KASSERT(pg->loan_count > 0);
pg->loan_count--;
pg->pqflags |= PQ_ANON;
/* anon now owns it */
}
}
return slock;
}
#if defined(VMSWAP)
struct swapcluster {
int swc_slot;
int swc_nallocated;
int swc_nused;
struct vm_page *swc_pages[howmany(MAXPHYS, MIN_PAGE_SIZE)];
};
static void
swapcluster_init(struct swapcluster *swc)
{
swc->swc_slot = 0;
}
static int
swapcluster_allocslots(struct swapcluster *swc)
{
int slot;
int npages;
if (swc->swc_slot != 0) {
return 0;
}
/* Even with strange MAXPHYS, the shift
implicitly rounds down to a page. */
npages = MAXPHYS >> PAGE_SHIFT;
slot = uvm_swap_alloc(&npages, true);
if (slot == 0) {
return ENOMEM;
}
swc->swc_slot = slot;
swc->swc_nallocated = npages;
swc->swc_nused = 0;
return 0;
}
static int
swapcluster_add(struct swapcluster *swc, struct vm_page *pg)
{
int slot;
struct uvm_object *uobj;
KASSERT(swc->swc_slot != 0);
KASSERT(swc->swc_nused < swc->swc_nallocated);
KASSERT((pg->pqflags & PQ_SWAPBACKED) != 0);
slot = swc->swc_slot + swc->swc_nused;
uobj = pg->uobject;
if (uobj == NULL) {
LOCK_ASSERT(simple_lock_held(&pg->uanon->an_lock));
pg->uanon->an_swslot = slot;
} else {
int result;
LOCK_ASSERT(simple_lock_held(&uobj->vmobjlock));
result = uao_set_swslot(uobj, pg->offset >> PAGE_SHIFT, slot);
if (result == -1) {
return ENOMEM;
}
}
swc->swc_pages[swc->swc_nused] = pg;
swc->swc_nused++;
return 0;
}
static void
swapcluster_flush(struct swapcluster *swc, bool now)
{
int slot;
int nused;
int nallocated;
int error;
if (swc->swc_slot == 0) {
return;
}
KASSERT(swc->swc_nused <= swc->swc_nallocated);
slot = swc->swc_slot;
nused = swc->swc_nused;
nallocated = swc->swc_nallocated;
/*
* if this is the final pageout we could have a few
* unused swap blocks. if so, free them now.
*/
if (nused < nallocated) {
if (!now) {
return;
}
uvm_swap_free(slot + nused, nallocated - nused);
}
/*
* now start the pageout.
*/
uvmexp.pdpageouts++;
error = uvm_swap_put(slot, swc->swc_pages, nused, 0);
KASSERT(error == 0);
/*
* zero swslot to indicate that we are
* no longer building a swap-backed cluster.
*/
swc->swc_slot = 0;
}
/*
* uvmpd_dropswap: free any swap allocated to this page.
*
* => called with owner locked.
* => return true if a page had an associated slot.
*/
static bool
uvmpd_dropswap(struct vm_page *pg)
{
bool result = false;
struct vm_anon *anon = pg->uanon;
if ((pg->pqflags & PQ_ANON) && anon->an_swslot) {
uvm_swap_free(anon->an_swslot, 1);
anon->an_swslot = 0;
pg->flags &= ~PG_CLEAN;
result = true;
} else if (pg->pqflags & PQ_AOBJ) {
int slot = uao_set_swslot(pg->uobject,
pg->offset >> PAGE_SHIFT, 0);
if (slot) {
uvm_swap_free(slot, 1);
pg->flags &= ~PG_CLEAN;
result = true;
}
}
return result;
}
/*
* uvmpd_trydropswap: try to free any swap allocated to this page.
*
* => return true if a slot is successfully freed.
*/
bool
uvmpd_trydropswap(struct vm_page *pg)
{
struct simplelock *slock;
bool result;
if ((pg->flags & PG_BUSY) != 0) {
return false;
}
/*
* lock the page's owner.
*/
slock = uvmpd_trylockowner(pg);
if (slock == NULL) {
return false;
}
/*
* skip this page if it's busy.
*/
if ((pg->flags & PG_BUSY) != 0) {
simple_unlock(slock);
return false;
}
result = uvmpd_dropswap(pg);
simple_unlock(slock);
return result;
}
#endif /* defined(VMSWAP) */
/*
* uvmpd_scan_queue: scan an replace candidate list for pages
* to clean or free.
*
* => called with page queues locked
* => we work on meeting our free target by converting inactive pages
* into free pages.
* => we handle the building of swap-backed clusters
*/
static void
uvmpd_scan_queue(void)
{
struct vm_page *p;
struct uvm_object *uobj;
struct vm_anon *anon;
#if defined(VMSWAP)
struct swapcluster swc;
#endif /* defined(VMSWAP) */
int dirtyreacts;
struct simplelock *slock;
UVMHIST_FUNC("uvmpd_scan_queue"); UVMHIST_CALLED(pdhist);
/*
* swslot is non-zero if we are building a swap cluster. we want
* to stay in the loop while we have a page to scan or we have
* a swap-cluster to build.
*/
#if defined(VMSWAP)
swapcluster_init(&swc);
#endif /* defined(VMSWAP) */
dirtyreacts = 0;
uvmpdpol_scaninit();
while (/* CONSTCOND */ 1) {
/*
* see if we've met the free target.
*/
if (uvmexp.free + uvmexp.paging >= uvmexp.freetarg << 2 ||
dirtyreacts == UVMPD_NUMDIRTYREACTS) {
UVMHIST_LOG(pdhist," met free target: "
"exit loop", 0, 0, 0, 0);
break;
}
p = uvmpdpol_selectvictim();
if (p == NULL) {
break;
}
KASSERT(uvmpdpol_pageisqueued_p(p));
KASSERT(p->wire_count == 0);
/*
* we are below target and have a new page to consider.
*/
anon = p->uanon;
uobj = p->uobject;
/*
* first we attempt to lock the object that this page
* belongs to. if our attempt fails we skip on to
* the next page (no harm done). it is important to
* "try" locking the object as we are locking in the
* wrong order (pageq -> object) and we don't want to
* deadlock.
*
* the only time we expect to see an ownerless page
* (i.e. a page with no uobject and !PQ_ANON) is if an
* anon has loaned a page from a uvm_object and the
* uvm_object has dropped the ownership. in that
* case, the anon can "take over" the loaned page
* and make it its own.
*/
slock = uvmpd_trylockowner(p);
if (slock == NULL) {
continue;
}
if (p->flags & PG_BUSY) {
simple_unlock(slock);
uvmexp.pdbusy++;
continue;
}
/* does the page belong to an object? */
if (uobj != NULL) {
uvmexp.pdobscan++;
} else {
#if defined(VMSWAP)
KASSERT(anon != NULL);
uvmexp.pdanscan++;
#else /* defined(VMSWAP) */
panic("%s: anon", __func__);
#endif /* defined(VMSWAP) */
}
/*
* we now have the object and the page queues locked.
* if the page is not swap-backed, call the object's
* pager to flush and free the page.
*/
#if defined(READAHEAD_STATS)
if ((p->pqflags & PQ_READAHEAD) != 0) {
p->pqflags &= ~PQ_READAHEAD;
uvm_ra_miss.ev_count++;
}
#endif /* defined(READAHEAD_STATS) */
if ((p->pqflags & PQ_SWAPBACKED) == 0) {
KASSERT(uobj != NULL);
uvm_unlock_pageq();
(void) (uobj->pgops->pgo_put)(uobj, p->offset,
p->offset + PAGE_SIZE, PGO_CLEANIT|PGO_FREE);
uvm_lock_pageq();
continue;
}
/*
* the page is swap-backed. remove all the permissions
* from the page so we can sync the modified info
* without any race conditions. if the page is clean
* we can free it now and continue.
*/
pmap_page_protect(p, VM_PROT_NONE);
if ((p->flags & PG_CLEAN) && pmap_clear_modify(p)) {
p->flags &= ~(PG_CLEAN);
}
if (p->flags & PG_CLEAN) {
int slot;
int pageidx;
pageidx = p->offset >> PAGE_SHIFT;
uvm_pagefree(p);
uvmexp.pdfreed++;
/*
* for anons, we need to remove the page
* from the anon ourselves. for aobjs,
* pagefree did that for us.
*/
if (anon) {
KASSERT(anon->an_swslot != 0);
anon->an_page = NULL;
slot = anon->an_swslot;
} else {
slot = uao_find_swslot(uobj, pageidx);
}
simple_unlock(slock);
if (slot > 0) {
/* this page is now only in swap. */
simple_lock(&uvm.swap_data_lock);
KASSERT(uvmexp.swpgonly < uvmexp.swpginuse);
uvmexp.swpgonly++;
simple_unlock(&uvm.swap_data_lock);
}
continue;
}
#if defined(VMSWAP)
/*
* this page is dirty, skip it if we'll have met our
* free target when all the current pageouts complete.
*/
if (uvmexp.free + uvmexp.paging > uvmexp.freetarg << 2) {
simple_unlock(slock);
continue;
}
/*
* free any swap space allocated to the page since
* we'll have to write it again with its new data.
*/
uvmpd_dropswap(p);
/*
* if all pages in swap are only in swap,
* the swap space is full and we can't page out
* any more swap-backed pages. reactivate this page
* so that we eventually cycle all pages through
* the inactive queue.
*/
if (uvm_swapisfull()) {
dirtyreacts++;
uvm_pageactivate(p);
simple_unlock(slock);
continue;
}
/*
* start new swap pageout cluster (if necessary).
*/
if (swapcluster_allocslots(&swc)) {
simple_unlock(slock);
dirtyreacts++; /* XXX */
continue;
}
/*
* at this point, we're definitely going reuse this
* page. mark the page busy and delayed-free.
* we should remove the page from the page queues
* so we don't ever look at it again.
* adjust counters and such.
*/
p->flags |= PG_BUSY;
UVM_PAGE_OWN(p, "scan_queue");
p->flags |= PG_PAGEOUT;
uvmexp.paging++;
uvm_pagedequeue(p);
uvmexp.pgswapout++;
uvm_unlock_pageq();
/*
* add the new page to the cluster.
*/
if (swapcluster_add(&swc, p)) {
p->flags &= ~(PG_BUSY|PG_PAGEOUT);
UVM_PAGE_OWN(p, NULL);
uvm_lock_pageq();
uvmexp.paging--;
dirtyreacts++;
uvm_pageactivate(p);
simple_unlock(slock);
continue;
}
simple_unlock(slock);
swapcluster_flush(&swc, false);
uvm_lock_pageq();
/*
* the pageout is in progress. bump counters and set up
* for the next loop.
*/
uvmexp.pdpending++;
#else /* defined(VMSWAP) */
uvm_pageactivate(p);
simple_unlock(slock);
#endif /* defined(VMSWAP) */
}
#if defined(VMSWAP)
uvm_unlock_pageq();
swapcluster_flush(&swc, true);
uvm_lock_pageq();
#endif /* defined(VMSWAP) */
}
/*
* uvmpd_scan: scan the page queues and attempt to meet our targets.
*
* => called with pageq's locked
*/
static void
uvmpd_scan(void)
{
int swap_shortage, pages_freed;
UVMHIST_FUNC("uvmpd_scan"); UVMHIST_CALLED(pdhist);
uvmexp.pdrevs++;
#ifndef __SWAP_BROKEN
/*
* swap out some processes if we are below our free target.
* we need to unlock the page queues for this.
*/
if (uvmexp.free < uvmexp.freetarg && uvmexp.nswapdev != 0) {
uvmexp.pdswout++;
UVMHIST_LOG(pdhist," free %d < target %d: swapout",
uvmexp.free, uvmexp.freetarg, 0, 0);
uvm_unlock_pageq();
uvm_swapout_threads();
uvm_lock_pageq();
}
#endif
/*
* now we want to work on meeting our targets. first we work on our
* free target by converting inactive pages into free pages. then
* we work on meeting our inactive target by converting active pages
* to inactive ones.
*/
UVMHIST_LOG(pdhist, " starting 'free' loop",0,0,0,0);
pages_freed = uvmexp.pdfreed;
uvmpd_scan_queue();
pages_freed = uvmexp.pdfreed - pages_freed;
/*
* detect if we're not going to be able to page anything out
* until we free some swap resources from active pages.
*/
swap_shortage = 0;
if (uvmexp.free < uvmexp.freetarg &&
uvmexp.swpginuse >= uvmexp.swpgavail &&
!uvm_swapisfull() &&
pages_freed == 0) {
swap_shortage = uvmexp.freetarg - uvmexp.free;
}
uvmpdpol_balancequeue(swap_shortage);
}
/*
* uvm_reclaimable: decide whether to wait for pagedaemon.
*
* => return true if it seems to be worth to do uvm_wait.
*
* XXX should be tunable.
* XXX should consider pools, etc?
*/
bool
uvm_reclaimable(void)
{
int filepages;
int active, inactive;
/*
* if swap is not full, no problem.
*/
if (!uvm_swapisfull()) {
return true;
}
/*
* file-backed pages can be reclaimed even when swap is full.
* if we have more than 1/16 of pageable memory or 5MB, try to reclaim.
*
* XXX assume the worst case, ie. all wired pages are file-backed.
*
* XXX should consider about other reclaimable memory.
* XXX ie. pools, traditional buffer cache.
*/
filepages = uvmexp.filepages + uvmexp.execpages - uvmexp.wired;
uvm_estimatepageable(&active, &inactive);
if (filepages >= MIN((active + inactive) >> 4,
5 * 1024 * 1024 >> PAGE_SHIFT)) {
return true;
}
/*
* kill the process, fail allocation, etc..
*/
return false;
}
void
uvm_estimatepageable(int *active, int *inactive)
{
uvmpdpol_estimatepageable(active, inactive);
}