* Copyright (c) 1997 Charles D. Cranor and Washington University.

/* $NetBSD: uvm_pdaemon.c,v 1.134 2023/09/10 15:01:11 ad 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. 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 [email protected]
* 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 1.134 2023/09/10 15:01:11 ad Exp $");

#include "opt_uvmhist.h"
#include "opt_readahead.h"

#define __RWLOCK_PRIVATE

#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 <sys/module.h>
#include <sys/atomic.h>
#include <sys/kthread.h>

#include <uvm/uvm.h>
#include <uvm/uvm_pdpolicy.h>
#include <uvm/uvm_pgflcache.h>

#ifdef UVMHIST
#ifndef UVMHIST_PDHIST_SIZE
#define UVMHIST_PDHIST_SIZE 100
#endif
static struct kern_history_ent pdhistbuf[UVMHIST_PDHIST_SIZE];
UVMHIST_DEFINE(pdhist) = UVMHIST_INITIALIZER(pdhisthist, pdhistbuf);
#endif

/*
* 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);
static void uvmpd_pool_drain_thread(void *);
static void uvmpd_pool_drain_wakeup(void);

static unsigned int uvm_pagedaemon_waiters;

/* State for the pool drainer thread */
static kmutex_t uvmpd_lock __cacheline_aligned;
static kcondvar_t uvmpd_pool_drain_cv;
static bool uvmpd_pool_drain_run = false;

/*
* XXX hack to avoid hangs when large processes fork.
*/
u_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;

if (uvm.pagedaemon_lwp == NULL)
panic("out of memory before the pagedaemon thread exists");

mutex_spin_enter(&uvmpd_lock);

/*
* check for page daemon going to sleep (waiting for itself)
*/

if (curlwp == uvm.pagedaemon_lwp && 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
}

uvm_pagedaemon_waiters++;
wakeup(&uvm.pagedaemon); /* wake the daemon! */
UVM_UNLOCK_AND_WAIT(&uvmexp.free, &uvmpd_lock, false, wmsg, timo);
}

/*
* 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)
{
int fpages = uvm_availmem(false);

if (fpages + uvmexp.paging < uvmexp.freemin ||
(fpages + uvmexp.paging < uvmexp.freetarg &&
uvmpdpol_needsscan_p()) ||
uvm_km_va_starved_p()) {
mutex_spin_enter(&uvmpd_lock);
wakeup(&uvm.pagedaemon);
mutex_spin_exit(&uvmpd_lock);
}
}

/*
* uvmpd_tune: tune paging parameters
*
* => called when ever memory is added (or removed?) to the system
*/

static void
uvmpd_tune(void)
{
int val;

UVMHIST_FUNC(__func__); UVMHIST_CALLED(pdhist);

/*
* try to keep 0.5% of available RAM free, but limit to between
* 128k and 1024k per-CPU. XXX: what are these values good for?
*/
val = uvmexp.npages / 200;
val = MAX(val, (128*1024) >> PAGE_SHIFT);
val = MIN(val, (1024*1024) >> PAGE_SHIFT);
val *= ncpu;

/* Make sure there's always a user page free. */
if (val < uvmexp.reserve_kernel + 1)
val = uvmexp.reserve_kernel + 1;
uvmexp.freemin = val;

/* Calculate free target. */
val = (uvmexp.freemin * 4) / 3;
if (val <= uvmexp.freemin)
val = uvmexp.freemin + 1;
uvmexp.freetarg = val + atomic_swap_uint(&uvm_extrapages, 0);

uvmexp.wiredmax = uvmexp.npages / 3;
UVMHIST_LOG(pdhist, "<- done, freemin=%jd, freetarg=%jd, wiredmax=%jd",
uvmexp.freemin, uvmexp.freetarg, uvmexp.wiredmax, 0);
}

/*
* uvm_pageout: the main loop for the pagedaemon
*/

void
uvm_pageout(void *arg)
{
int npages = 0;
int extrapages = 0;
int fpages;

UVMHIST_FUNC(__func__); UVMHIST_CALLED(pdhist);

UVMHIST_LOG(pdhist,"<starting uvm pagedaemon>", 0, 0, 0, 0);

mutex_init(&uvmpd_lock, MUTEX_DEFAULT, IPL_VM);
cv_init(&uvmpd_pool_drain_cv, "pooldrain");

/* Create the pool drainer kernel thread. */
if (kthread_create(PRI_VM, KTHREAD_MPSAFE, NULL,
uvmpd_pool_drain_thread, NULL, NULL, "pooldrain"))
panic("fork pooldrain");

/*
* ensure correct priority and set paging parameters...
*/

uvm.pagedaemon_lwp = curlwp;
npages = uvmexp.npages;
uvmpd_tune();

/*
* main loop
*/

for (;;) {
bool needsscan, needsfree, kmem_va_starved;

kmem_va_starved = uvm_km_va_starved_p();

mutex_spin_enter(&uvmpd_lock);
if ((uvm_pagedaemon_waiters == 0 || uvmexp.paging > 0) &&
!kmem_va_starved) {
UVMHIST_LOG(pdhist," <<SLEEPING>>",0,0,0,0);
UVM_UNLOCK_AND_WAIT(&uvm.pagedaemon,
&uvmpd_lock, false, "pgdaemon", 0);
uvmexp.pdwoke++;
UVMHIST_LOG(pdhist," <<WOKE UP>>",0,0,0,0);
} else {
mutex_spin_exit(&uvmpd_lock);
}

/*
* now recompute inactive count
*/

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.
*/
fpages = uvm_availmem(false);
UVMHIST_LOG(pdhist," free/ftarg=%jd/%jd",
fpages, uvmexp.freetarg, 0,0);

needsfree = fpages + uvmexp.paging < uvmexp.freetarg;
needsscan = needsfree || uvmpdpol_needsscan_p();

/*
* scan if needed
*/
if (needsscan) {
uvmpd_scan();
}

/*
* if there's any free memory to be had,
* wake up any waiters.
*/
if (uvm_availmem(false) > uvmexp.reserve_kernel ||
uvmexp.paging == 0) {
mutex_spin_enter(&uvmpd_lock);
wakeup(&uvmexp.free);
uvm_pagedaemon_waiters = 0;
mutex_spin_exit(&uvmpd_lock);
}

/*
* scan done. if we don't need free memory, we're done.
*/

if (!needsfree && !kmem_va_starved)
continue;

/*
* kick the pool drainer thread.
*/

uvmpd_pool_drain_wakeup();
}
/*NOTREACHED*/
}

void
uvm_pageout_start(int npages)
{

atomic_add_int(&uvmexp.paging, npages);
}

void
uvm_pageout_done(int npages)
{

KASSERT(atomic_load_relaxed(&uvmexp.paging) >= npages);

if (npages == 0) {
return;
}

atomic_add_int(&uvmexp.paging, -npages);

/*
* wake up either of pagedaemon or LWPs waiting for it.
*/

mutex_spin_enter(&uvmpd_lock);
if (uvm_availmem(false) <= uvmexp.reserve_kernel) {
wakeup(&uvm.pagedaemon);
} else if (uvm_pagedaemon_waiters != 0) {
wakeup(&uvmexp.free);
uvm_pagedaemon_waiters = 0;
}
mutex_spin_exit(&uvmpd_lock);
}

static krwlock_t *
uvmpd_page_owner_lock(struct vm_page *pg)
{
struct uvm_object *uobj = pg->uobject;
struct vm_anon *anon = pg->uanon;
krwlock_t *slock;

KASSERT(mutex_owned(&pg->interlock));

#ifdef DEBUG
if (uobj == (void *)0xdeadbeef || anon == (void *)0xdeadbeef) {
return NULL;
}
#endif
if (uobj != NULL) {
slock = uobj->vmobjlock;
KASSERTMSG(slock != NULL, "pg %p uobj %p, NULL lock", pg, uobj);
} else if (anon != NULL) {
slock = anon->an_lock;
KASSERTMSG(slock != NULL, "pg %p anon %p, NULL lock", pg, anon);
} else {
slock = NULL;
}
return slock;
}

/*
* uvmpd_trylockowner: trylock the page's owner.
*
* => called with page interlock held.
* => resolve orphaned O->A loaned page.
* => return the locked mutex on success. otherwise, return NULL.
*/

krwlock_t *
uvmpd_trylockowner(struct vm_page *pg)
{
krwlock_t *slock, *heldslock = NULL;

KASSERT(mutex_owned(&pg->interlock));

slock = uvmpd_page_owner_lock(pg);
if (slock == NULL) {
/* Page may be in state of flux - ignore. */
mutex_exit(&pg->interlock);
return NULL;
}

if (rw_tryenter(slock, RW_WRITER)) {
goto success;
}

/*
* The try-lock didn't work, so now do a blocking lock after
* dropping the page interlock. Prevent the owner lock from
* being freed by taking a hold on it first.
*/

rw_obj_hold(slock);
mutex_exit(&pg->interlock);
rw_enter(slock, RW_WRITER);
heldslock = slock;

/*
* Now we hold some owner lock. Check if the lock we hold
* is still the lock for the owner of the page.
* If it is then return it, otherwise release it and return NULL.
*/

mutex_enter(&pg->interlock);
slock = uvmpd_page_owner_lock(pg);
if (heldslock != slock) {
rw_exit(heldslock);
slock = NULL;
} else {
success:
/*
* Set PG_ANON if it isn't set already.
*/
if (pg->uobject == NULL && (pg->flags & PG_ANON) == 0) {
KASSERT(pg->loan_count > 0);
pg->loan_count--;
pg->flags |= PG_ANON;
/* anon now owns it */
}
}
mutex_exit(&pg->interlock);
if (heldslock != NULL) {
rw_obj_free(heldslock);
}
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;
swc->swc_nused = 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->flags & PG_SWAPBACKED) != 0);

slot = swc->swc_slot + swc->swc_nused;
uobj = pg->uobject;
if (uobj == NULL) {
KASSERT(rw_write_held(pg->uanon->an_lock));
pg->uanon->an_swslot = slot;
} else {
int result;

KASSERT(rw_write_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 __diagused;

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.
*/

if (nused > 0) {
uvmexp.pdpageouts++;
uvm_pageout_start(nused);
error = uvm_swap_put(slot, swc->swc_pages, nused, 0);
KASSERT(error == 0 || error == ENOMEM);
}

/*
* zero swslot to indicate that we are
* no longer building a swap-backed cluster.
*/

swc->swc_slot = 0;
swc->swc_nused = 0;
}

static int
swapcluster_nused(struct swapcluster *swc)
{

return swc->swc_nused;
}

/*
* uvmpd_dropswap: free any swap allocated to this page.
*
* => called with owner locked.
* => return true if a page had an associated slot.
*/

bool
uvmpd_dropswap(struct vm_page *pg)
{
bool result = false;
struct vm_anon *anon = pg->uanon;

if ((pg->flags & PG_ANON) && anon->an_swslot) {
uvm_swap_free(anon->an_swslot, 1);
anon->an_swslot = 0;
uvm_pagemarkdirty(pg, UVM_PAGE_STATUS_DIRTY);
result = true;
} else if (pg->flags & PG_AOBJ) {
int slot = uao_set_swslot(pg->uobject,
pg->offset >> PAGE_SHIFT, 0);
if (slot) {
uvm_swap_free(slot, 1);
uvm_pagemarkdirty(pg, UVM_PAGE_STATUS_DIRTY);
result = true;
}
}

return result;
}

#endif /* defined(VMSWAP) */

/*
* uvmpd_scan_queue: scan an replace candidate list for pages
* to clean or free.
*
* => 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;
krwlock_t *slock;
UVMHIST_FUNC(__func__); 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 (uvm_availmem(false) + uvmexp.paging
#if defined(VMSWAP)
+ swapcluster_nused(&swc)
#endif /* defined(VMSWAP) */
>= uvmexp.freetarg << 2 ||
dirtyreacts == UVMPD_NUMDIRTYREACTS) {
UVMHIST_LOG(pdhist," met free target: "
"exit loop", 0, 0, 0, 0);
break;
}

/*
* first we have the pdpolicy select a victim page
* and attempt to lock the object that the 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 !PG_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.
*/

p = uvmpdpol_selectvictim(&slock);
if (p == NULL) {
break;
}
KASSERT(uvmpdpol_pageisqueued_p(p));
KASSERT(uvm_page_owner_locked_p(p, true));
KASSERT(p->wire_count == 0);

/*
* we are below target and have a new page to consider.
*/

anon = p->uanon;
uobj = p->uobject;

if (p->flags & PG_BUSY) {
rw_exit(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 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->flags & PG_READAHEAD) != 0) {
p->flags &= ~PG_READAHEAD;
uvm_ra_miss.ev_count++;
}
#endif /* defined(READAHEAD_STATS) */

if ((p->flags & PG_SWAPBACKED) == 0) {
KASSERT(uobj != NULL);
(void) (uobj->pgops->pgo_put)(uobj, p->offset,
p->offset + PAGE_SIZE, PGO_CLEANIT|PGO_FREE);
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 (uvm_pagegetdirty(p) == UVM_PAGE_STATUS_UNKNOWN) {
if (pmap_clear_modify(p)) {
uvm_pagemarkdirty(p, UVM_PAGE_STATUS_DIRTY);
} else {
uvm_pagemarkdirty(p, UVM_PAGE_STATUS_CLEAN);
}
}
if (uvm_pagegetdirty(p) != UVM_PAGE_STATUS_DIRTY) {
int slot;
int pageidx;

pageidx = p->offset >> PAGE_SHIFT;
uvm_pagefree(p);
atomic_inc_uint(&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);
}
if (slot > 0) {
/* this page is now only in swap. */
KASSERT(uvmexp.swpgonly < uvmexp.swpginuse);
atomic_inc_uint(&uvmexp.swpgonly);
}
rw_exit(slock);
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 (uvm_availmem(false) + uvmexp.paging >
uvmexp.freetarg << 2) {
rw_exit(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);

/*
* start new swap pageout cluster (if necessary).
*
* if swap is full reactivate this page so that
* we eventually cycle all pages through the
* inactive queue.
*/

if (swapcluster_allocslots(&swc)) {
dirtyreacts++;
uvm_pagelock(p);
uvm_pageactivate(p);
uvm_pageunlock(p);
rw_exit(slock);
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.pgswapout++;

uvm_pagelock(p);
uvm_pagedequeue(p);
uvm_pageunlock(p);

/*
* add the new page to the cluster.
*/

if (swapcluster_add(&swc, p)) {
p->flags &= ~(PG_BUSY|PG_PAGEOUT);
UVM_PAGE_OWN(p, NULL);
dirtyreacts++;
uvm_pagelock(p);
uvm_pageactivate(p);
uvm_pageunlock(p);
rw_exit(slock);
continue;
}
rw_exit(slock);

swapcluster_flush(&swc, false);

/*
* the pageout is in progress. bump counters and set up
* for the next loop.
*/

atomic_inc_uint(&uvmexp.pdpending);

#else /* defined(VMSWAP) */
uvm_pagelock(p);
uvm_pageactivate(p);
uvm_pageunlock(p);
rw_exit(slock);
#endif /* defined(VMSWAP) */
}

uvmpdpol_scanfini();

#if defined(VMSWAP)
swapcluster_flush(&swc, true);
#endif /* defined(VMSWAP) */
}

/*
* uvmpd_scan: scan the page queues and attempt to meet our targets.
*/

static void
uvmpd_scan(void)
{
int swap_shortage, pages_freed, fpages;
UVMHIST_FUNC(__func__); UVMHIST_CALLED(pdhist);

uvmexp.pdrevs++;

/*
* 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;
fpages = uvm_availmem(false);
if (fpages < uvmexp.freetarg &&
uvmexp.swpginuse >= uvmexp.swpgavail &&
!uvm_swapisfull() &&
pages_freed == 0) {
swap_shortage = uvmexp.freetarg - fpages;
}

uvmpdpol_balancequeue(swap_shortage);

/*
* if still below the minimum target, try unloading kernel
* modules.
*/

if (uvm_availmem(false) < uvmexp.freemin) {
module_thread_kick();
}
}

/*
* 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.
* NB: filepages calculation does not exclude EXECPAGES - intentional.
*
* 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.
*/

cpu_count_sync(false);
filepages = (int)(cpu_count_get(CPU_COUNT_FILECLEAN) +
cpu_count_get(CPU_COUNT_FILEUNKNOWN) +
cpu_count_get(CPU_COUNT_FILEDIRTY) - 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);
}

/*
* Use a separate thread for draining pools.
* This work can't done from the main pagedaemon thread because
* some pool allocators need to take vm_map locks.
*/

static void
uvmpd_pool_drain_thread(void *arg)
{
struct pool *firstpool, *curpool;
int bufcnt, lastslept;
bool cycled;

firstpool = NULL;
cycled = true;
for (;;) {
/*
* sleep until awoken by the pagedaemon.
*/
mutex_enter(&uvmpd_lock);
if (!uvmpd_pool_drain_run) {
lastslept = getticks();
cv_wait(&uvmpd_pool_drain_cv, &uvmpd_lock);
if (getticks() != lastslept) {
cycled = false;
firstpool = NULL;
}
}
uvmpd_pool_drain_run = false;
mutex_exit(&uvmpd_lock);

/*
* rate limit draining, otherwise in desperate circumstances
* this can totally saturate the system with xcall activity.
*/
if (cycled) {
kpause("uvmpdlmt", false, 1, NULL);
cycled = false;
firstpool = NULL;
}

/*
* drain and temporarily disable the freelist cache.
*/
uvm_pgflcache_pause();

/*
* kill unused metadata buffers.
*/
bufcnt = uvmexp.freetarg - uvm_availmem(false);
if (bufcnt < 0)
bufcnt = 0;

mutex_enter(&bufcache_lock);
buf_drain(bufcnt << PAGE_SHIFT);
mutex_exit(&bufcache_lock);

/*
* drain a pool, and then re-enable the freelist cache.
*/
(void)pool_drain(&curpool);
KASSERT(curpool != NULL);
if (firstpool == NULL) {
firstpool = curpool;
} else if (firstpool == curpool) {
cycled = true;
}
uvm_pgflcache_resume();
}
/*NOTREACHED*/
}

static void
uvmpd_pool_drain_wakeup(void)
{

mutex_enter(&uvmpd_lock);
uvmpd_pool_drain_run = true;
cv_signal(&uvmpd_pool_drain_cv);
mutex_exit(&uvmpd_lock);
}