ref: 428cc541f822e6f49ce26d970b5b030e8b1b696d
dir: /sys/src/9/port/swap.c/
#include "u.h"
#include "../port/lib.h"
#include "mem.h"
#include "dat.h"
#include "fns.h"
#include "../port/error.h"
static int canflush(Proc*, Segment*);
static void executeio(void);
static int needpages(void*);
static void pageout(Proc*, Segment*);
static void pagepte(int, Page**);
static void pager(void*);
Image swapimage;
static int swopen;
static Page **iolist;
static int ioptr;
static ulong genage, genclock, gencount;
static uvlong gensum;
static void
gentick(void)
{
genclock++;
if(gencount)
genage = gensum / gencount;
else
genage = 0;
gensum = gencount = 0;
}
void
swapinit(void)
{
swapalloc.swmap = xalloc(conf.nswap);
swapalloc.top = &swapalloc.swmap[conf.nswap];
swapalloc.alloc = swapalloc.swmap;
swapalloc.last = swapalloc.swmap;
swapalloc.free = conf.nswap;
swapalloc.xref = 0;
iolist = xalloc(conf.nswppo*sizeof(Page*));
if(swapalloc.swmap == 0 || iolist == 0)
panic("swapinit: not enough memory");
swapimage.notext = 1;
}
uintptr
newswap(void)
{
uchar *look;
lock(&swapalloc);
if(swapalloc.free == 0) {
unlock(&swapalloc);
return ~0;
}
look = memchr(swapalloc.last, 0, swapalloc.top-swapalloc.last);
if(look == 0)
panic("inconsistent swap");
*look = 1;
swapalloc.last = look;
swapalloc.free--;
unlock(&swapalloc);
return (look-swapalloc.swmap) * BY2PG;
}
void
putswap(Page *p)
{
uchar *idx;
lock(&swapalloc);
idx = &swapalloc.swmap[((uintptr)p)/BY2PG];
if(*idx == 0)
panic("putswap %#p ref == 0", p);
if(*idx == 255) {
if(swapalloc.xref == 0)
panic("putswap %#p xref == 0", p);
if(--swapalloc.xref == 0) {
for(idx = swapalloc.swmap; idx < swapalloc.top; idx++) {
if(*idx == 255) {
*idx = 0;
swapalloc.free++;
if(idx < swapalloc.last)
swapalloc.last = idx;
}
}
}
} else {
if(--(*idx) == 0) {
swapalloc.free++;
if(idx < swapalloc.last)
swapalloc.last = idx;
}
}
unlock(&swapalloc);
}
void
dupswap(Page *p)
{
uchar *idx;
lock(&swapalloc);
idx = &swapalloc.swmap[((uintptr)p)/BY2PG];
if(*idx == 255)
swapalloc.xref++;
else {
if(++(*idx) == 255)
swapalloc.xref += 255;
}
unlock(&swapalloc);
}
int
swapcount(uintptr daddr)
{
return swapalloc.swmap[daddr/BY2PG];
}
void
kickpager(void)
{
static int started;
if(started)
wakeup(&swapalloc.r);
else {
kproc("pager", pager, 0);
started = 1;
}
}
static void
pager(void *junk)
{
int i;
Segment *s;
Proc *p, *ep;
p = proctab(0);
ep = &p[conf.nproc];
while(waserror())
;
loop:
up->psstate = "Idle";
wakeup(&palloc.r);
sleep(&swapalloc.r, needpages, 0);
while(needpages(junk)) {
if(swapimage.c && swapalloc.free) {
p++;
if(p >= ep){
p = proctab(0);
gentick();
}
if(p->state == Dead || p->noswap)
continue;
if(!canqlock(&p->seglock))
continue; /* process changing its segments */
for(i = 0; i < NSEG; i++) {
if(!needpages(junk)){
qunlock(&p->seglock);
goto loop;
}
if(s = p->seg[i]) {
switch(s->type&SG_TYPE) {
default:
break;
case SG_TEXT:
pageout(p, s);
break;
case SG_DATA:
case SG_BSS:
case SG_STACK:
case SG_SHARED:
up->psstate = "Pageout";
pageout(p, s);
if(ioptr != 0) {
up->psstate = "I/O";
executeio();
}
break;
}
}
}
qunlock(&p->seglock);
} else {
killbig("out of memory");
freebroken(); /* can use the memory */
sched();
}
}
goto loop;
}
static void
pageout(Proc *p, Segment *s)
{
int type, i, size;
ulong age;
Pte *l;
Page **pg, *entry;
if(!canqlock(&s->lk)) /* We cannot afford to wait, we will surely deadlock */
return;
if(s->steal) { /* Protected by /dev/proc */
qunlock(&s->lk);
return;
}
if(!canflush(p, s)) { /* Able to invalidate all tlbs with references */
qunlock(&s->lk);
putseg(s);
return;
}
if(waserror()) {
qunlock(&s->lk);
putseg(s);
return;
}
/* Pass through the pte tables looking for memory pages to swap out */
type = s->type&SG_TYPE;
size = s->mapsize;
for(i = 0; i < size; i++) {
l = s->map[i];
if(l == 0)
continue;
for(pg = l->first; pg < l->last; pg++) {
entry = *pg;
if(pagedout(entry))
continue;
if(entry->modref & PG_REF) {
entry->modref &= ~PG_REF;
entry->gen = genclock;
}
if(genclock < entry->gen)
age = ~(entry->gen - genclock);
else
age = genclock - entry->gen;
gensum += age;
gencount++;
if(age <= genage)
continue;
pagepte(type, pg);
if(ioptr >= conf.nswppo)
goto out;
}
}
out:
poperror();
qunlock(&s->lk);
putseg(s);
}
static int
canflush(Proc *p, Segment *s)
{
int i;
Proc *ep;
lock(s);
if(s->ref == 1) { /* Easy if we are the only user */
s->ref++;
unlock(s);
return canpage(p);
}
s->ref++;
unlock(s);
/* Now we must do hardwork to ensure all processes which have tlb
* entries for this segment will be flushed if we succeed in paging it out
*/
p = proctab(0);
ep = &p[conf.nproc];
while(p < ep) {
if(p->state != Dead) {
for(i = 0; i < NSEG; i++)
if(p->seg[i] == s)
if(!canpage(p))
return 0;
}
p++;
}
return 1;
}
static void
pagepte(int type, Page **pg)
{
uintptr daddr;
Page *outp;
outp = *pg;
switch(type) {
case SG_TEXT: /* Revert to demand load */
putpage(outp);
*pg = 0;
break;
case SG_DATA:
case SG_BSS:
case SG_STACK:
case SG_SHARED:
/*
* get a new swap address and clear any pages
* referring to it from the cache
*/
daddr = newswap();
if(daddr == ~0)
break;
cachedel(&swapimage, daddr);
lock(outp);
/* forget anything that it used to cache */
uncachepage(outp);
/*
* incr the reference count to make sure it sticks around while
* being written
*/
outp->ref++;
/*
* enter it into the cache so that a fault happening
* during the write will grab the page from the cache
* rather than one partially written to the disk
*/
outp->daddr = daddr;
cachepage(outp, &swapimage);
*pg = (Page*)(daddr|PG_ONSWAP);
unlock(outp);
/* Add page to IO transaction list */
iolist[ioptr++] = outp;
break;
}
}
void
pagersummary(void)
{
print("%lud/%lud memory %lud/%lud swap %d iolist\n",
palloc.user-palloc.freecount,
palloc.user, conf.nswap-swapalloc.free, conf.nswap,
ioptr);
}
static int
pageiocomp(void *a, void *b)
{
Page *p1, *p2;
p1 = *(Page **)a;
p2 = *(Page **)b;
if(p1->daddr > p2->daddr)
return 1;
else
return -1;
}
static void
executeio(void)
{
Page *out;
int i, n;
Chan *c;
char *kaddr;
KMap *k;
c = swapimage.c;
qsort(iolist, ioptr, sizeof iolist[0], pageiocomp);
for(i = 0; i < ioptr; i++) {
if(ioptr > conf.nswppo)
panic("executeio: ioptr %d > %d", ioptr, conf.nswppo);
out = iolist[i];
k = kmap(out);
kaddr = (char*)VA(k);
if(waserror())
panic("executeio: page out I/O error");
n = devtab[c->type]->write(c, kaddr, BY2PG, out->daddr);
if(n != BY2PG)
nexterror();
kunmap(k);
poperror();
/* Free up the page after I/O */
lock(out);
out->ref--;
unlock(out);
putpage(out);
}
ioptr = 0;
}
static int
needpages(void*)
{
return palloc.freecount < swapalloc.headroom;
}
void
setswapchan(Chan *c)
{
uchar dirbuf[sizeof(Dir)+100];
Dir d;
int n;
if(swapimage.c) {
if(swapalloc.free != conf.nswap){
cclose(c);
error(Einuse);
}
cclose(swapimage.c);
swapimage.c = nil;
}
/*
* if this isn't a file, set the swap space
* to be at most the size of the partition
*/
if(devtab[c->type]->dc != L'M'){
n = devtab[c->type]->stat(c, dirbuf, sizeof dirbuf);
if(n <= 0){
cclose(c);
error("stat failed in setswapchan");
}
convM2D(dirbuf, n, &d, nil);
if(d.length < conf.nswap*BY2PG){
conf.nswap = d.length/BY2PG;
swapalloc.top = &swapalloc.swmap[conf.nswap];
swapalloc.free = conf.nswap;
}
}
c->flag &= ~CCACHE;
swapimage.c = c;
}
int
swapfull(void)
{
return swapalloc.free < conf.nswap/10;
}