1991/0928/port/swap.c (diff list | history)

port/swap.c on 1991/0705
1991/0705		#include "u.h" #include "lib.h" #include "mem.h" #include "dat.h" #include "fns.h" #include "ureg.h" #include "errno.h" /* Predeclaration */ void pageout(Proc *p, Segment*); int pagepte(int, Segment*, Page**); int needpages(void*); void pager(void*); void executeio(void); int canflush(Proc *p, Segment*); enum {
1991/0706		Maxpages = 500, /* Max number of pageouts per segment pass */
1991/0705		}; Image swapimage; static int swopen; Page *iolist[Maxpages]; int ioptr; void swapinit(void) { swapalloc.swmap = ialloc(conf.nswap, 0); swapalloc.top = &swapalloc.swmap[conf.nswap]; swapalloc.alloc = swapalloc.swmap; swapalloc.free = conf.nswap; } ulong newswap(void) { char *look; int n; lock(&swapalloc); if(swapalloc.free == 0) panic("out of swap space"); n = swapalloc.top - swapalloc.alloc; look = swapalloc.alloc; while(n && *look) { n--; look++; } if(n == 0) { look = swapalloc.swmap; while(*look) look++; } if(look == swapalloc.top) swapalloc.alloc = swapalloc.swmap; else swapalloc.alloc = look+1; *look = 1;
1991/0928		swapalloc.free--;
1991/0705		unlock(&swapalloc); return (look-swapalloc.swmap) * BY2PG; } void putswap(Page *p) { lock(&swapalloc); if(--swapalloc.swmap[((ulong)p)/BY2PG] == 0) swapalloc.free++; unlock(&swapalloc); } void dupswap(Page *p) { lock(&swapalloc); swapalloc.swmap[((ulong)p)/BY2PG]++; unlock(&swapalloc); } void kickpager(void) { static int started; if(started) wakeup(&swapalloc.r); else { kproc("pager", pager, 0); started = 1; } } void pager(void *junk) { Proc *p, *ep; Segment *s; int i; p = proctab(0); ep = &p[conf.nproc]; for(;;) { if(waserror()) panic("pager: os error\n"); for(p = proctab(0); p < ep; p++) { if(p->state == Dead || p->kp) continue;
1991/0926		u->p->psstate = "Idle";
1991/0705		sleep(&swapalloc.r, needpages, 0);
1991/0926		u->p->psstate = "Pageout";
1991/0705
1991/0726		if(p->state == Dead || p->kp) continue;
1991/0705		if(swapimage.c) { for(i = 0; i < NSEG; i++) if(s = p->seg[i]) { pageout(p, s); executeio(); } }
1991/0727		else if(palloc.freecount < HIGHWATER) {
1991/0705		/* Emulate the old system if no swap channel */ print("no physical memory\n"); tsleep(&swapalloc.r, return0, 0, 1000); wakeup(&palloc.r); } } poperror(); } } void pageout(Proc *p, Segment *s) { Pte **sm, **endsm; Page **pg, **epg; int type; if(!canqlock(&s->lk)) /* We cannot afford to wait, we will surely deadlock */ return; if(!canflush(p, s) || s->steal) { 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; endsm = &s->map[SEGMAPSIZE]; for(sm = s->map; sm < endsm && ioptr < Maxpages; sm++) if(*sm) { pg = (*sm)->pages; for(epg = &pg[PTEPERTAB]; pg < epg && ioptr < Maxpages; pg++) if(!pagedout(*pg)) { if((*pg)->modref & PG_REF) (*pg)->modref &= ~PG_REF; else if(pagepte(type, s, pg) == 0) break; } } poperror(); qunlock(&s->lk); putseg(s); wakeup(&palloc.r); } int canflush(Proc *p, Segment *s) { Proc *ep; int i; 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
1991/0706		* entries for this segment will be flushed if we suceed in pageing it out
1991/0705		*/ p = proctab(0); ep = &p[conf.nproc]; for(; p < ep; p++) if(p->state != Dead) for(i = 0; i < NSEG; i++) if(p->seg[i] == s) if(!canpage(p)) return 0; return 1; } int pagepte(int type, Segment *s, Page **pg) { ulong daddr; char *kaddr; int n; Chan *c; Page *outp; KMap *k; outp = *pg; switch(type) { case SG_TEXT: /* Revert to demand load */ putpage(outp); *pg = 0; break; case SG_DATA: /* Unmodified data may be reverted to a demand load record if it * is not the last page in the DSEG */ /* BUG: needs to check the last page if((outp->modref&PG_MOD) == 0) { putpage(outp); *pg = 0; break; } */ /* NO break */ case SG_BSS: case SG_STACK: case SG_SHARED: lockpage(outp); outp->ref++; uncachepage(outp); unlockpage(outp); daddr = newswap(); outp->daddr = daddr; /* Enter swap page into cache before segment is unlocked so that * a fault will cause a cache recovery rather than a pagein on a * partially written block. */ cachepage(outp, &swapimage); *pg = (Page*)(daddr|PG_ONSWAP); /* Add me to IO transaction list */ iolist[ioptr++] = outp; } return 1; } void executeio(void) { Page *out; int i, n; Chan *c; char *kaddr; KMap *k; c = swapimage.c; for(i = 0; i < ioptr; i++) { out = iolist[i]; if(out->ref > 2) { lockpage(out); if(out->ref > 2) { /* Page was reclaimed, abort io */ out->ref -= 2; unlockpage(out); continue; } unlockpage(out); } k = kmap(out); kaddr = (char*)VA(k); qlock(&c->wrl); /* BUG: what to do ? Nobody to tell, nowhere to go: open to suggestions * the problem is I do not know whose page this is. */ if(waserror()) panic("executeio: page out I/O error"); n = (*devtab[c->type].write)(c, kaddr, BY2PG, out->daddr); if(n != BY2PG) nexterror(); qunlock(&c->wrl); kunmap(k); poperror(); /* Free up the page after I/O */ lockpage(out); out->ref--; unlockpage(out); putpage(out); } ioptr = 0; } int needpages(void *p) { return palloc.freecount < HIGHWATER+MAXHEADROOM; } void setswapchan(Chan *c) { if(swapimage.c) { if(swapalloc.free != conf.nswap) errors("swap channel busy"); close(swapimage.c); } incref(c); swapimage.c = c; }