- set daddr to ~0 by default
- don't try silly things in the pager that clearly can't work

Reference: /n/atom/patch/applied/pagerclean
Date: Thu Jun 12 04:50:00 CES 2014
Signed-off-by: quanstro@quanstro.net

--- /sys/src/nix/port/page.c	Thu Jun 12 04:49:29 2014
+++ /sys/src/nix/port/page.c	Thu Jun 12 04:49:33 2014
@@ -106,6 +106,7 @@
 	pg->pgszi = si;	/* size index */
 	incref(&pga.pgsza[si].npages);
 	pg->color = color;
+	pg->ref = 1;
 	return pg;
 }
 
@@ -199,9 +200,10 @@
 	KMap *k;
 	Pgsza *pa;
 	int i, dontalloc, si;
-	static int once;
 
 	si = getpgszi(size);
+	if(si == -1)
+		panic("newpage: getpgszi %lux %d %#p", size, color, getcallerpc(&size));
 	pa = &pga.pgsza[si];
 
 	lock(&pga);
@@ -222,19 +224,22 @@
 			pageunchain(p);
 			break;
 		}
+		unlock(&pga);
 
 		/*
 		 * 2. try to allocate a new one from physical memory
 		 */
 		p = pgalloc(size, color);
-		if(p != nil)
-			break;
+		if(p != nil){
+			p->va = va;
+			p->daddr = ~0;
+			goto Clear;
+		}
 
 		/*
 		 * 3. out of memory, try with the pager.
 		 * but release the segment (if any) while in the pager.
 		 */
-		unlock(&pga);
 
 		dontalloc = 0;
 		if(s != nil && *s != nil) {
@@ -265,11 +270,13 @@
 	p->ref++;
 	p->va = va;
 	p->modref = 0;
+	p->daddr = ~0;
 	for(i = 0; i < nelem(p->cachectl); i++)
 		p->cachectl[i] = PG_NEWCOL;
 	unlock(p);
 	unlock(&pga);
 
+Clear:
 	if(clear) {
 		k = kmap(p);
 		memset((void*)VA(k), 0, m->pgsz[p->pgszi]);
@@ -314,9 +321,9 @@
 	if(pga.r.p != nil)
 		wakeup(&pga.r);
 	unlock(p);
+	unlock(&pga);
 	if(rlse)
 		pgfree(p);
-	unlock(&pga);
 }
 
 /*
@@ -381,14 +388,16 @@
 	for(f = *l; f; f = f->hash){
 		if(f == p){
 			*l = p->hash;
-			break;
+			goto found;
 		}
 		l = &f->hash;
 	}
+	panic("uncachpage");
+found:
 	unlock(&pga.hashlock);
 	putimage(p->image);
 	p->image = 0;
-	p->daddr = 0;
+	p->daddr = ~0;
 }
 
 void
--- /sys/src/nix/port/pager.c	Thu Jun 12 04:49:40 2014
+++ /sys/src/nix/port/pager.c	Thu Jun 12 04:49:42 2014
@@ -208,9 +208,7 @@
 
 	p = pgalloc(m->pgsz[pgszi], color);
 	if(p != nil){
-		lock(&pga);
-		pagechainhead(p);
-		unlock(&pga);
+		putpage(p);
 		return 0;
 	}
 	return -1;
@@ -243,36 +241,21 @@
 {
 	Pgsza *pa;
 
-	if(DBGFLG>1)
-		DBG("kickpager() %#p\n", up);
+	DBG("kickpager: %s:%d color %d\n", up->text, up->pid, color);
 	if(waserror())
 		panic("error in kickpager");
 	qlock(&pagerlck);
 	pa = &pga.pgsza[pgszi];
 
 	/*
-	 * 1. did anyone else release one for us in the mean time?
-	 */
-	if(hascolor(pa->head, color))
-		goto Done;
-
-	/*
-	 * 2. try allocating from physical memory
-	 */
-	tryalloc(pgszi, color);
-	if(hascolor(pa->head, color))
-		goto Done;
-
-	/*
 	 * If pgszi is <= text page size, try releasing text pages.
 	 */
 	if(m->pgsz[pgszi] <= 2*MiB){
 		pstats.ntext++;
 		DBG("kickpager() up %#p: reclaiming text pages\n", up);
 		pageouttext(pgszi, color);
-		tryalloc(pgszi, color);
-		if(hascolor(pa->head, color)){
-			DBG("kickpager() found %ud free\n", pa->freecount);
+		if(tryalloc(pgszi, color) == 0){
+			DBG("kickpager: pageouttext found %ud free\n", pa->freecount);
 			goto Done;
 		}
 	}
@@ -282,9 +265,8 @@
 	 */
 	pstats.nbig++;
 	freepages(pgszi+1, 1);
-	tryalloc(pgszi, color);
-	if(hascolor(pa->head, color)){
-		DBG("kickpager() found %ud free\n", pa->freecount);
+	if(tryalloc(pgszi, color) == 0){
+		DBG("kickpager: big found %ud free\n", pa->freecount);
 		goto Done;
 	}
 
@@ -294,9 +276,8 @@
 	pstats.nall++;
 	DBG("kickpager() up %#p: releasing all pages\n", up);
 	freepages(0, 0);
-	tryalloc(pgszi, color);
-	if(pa->freecount > 0){
-		DBG("kickpager() found %ud free\n", pa->freecount);
+	if(tryalloc(pgszi, color) == 0){
+		DBG("kickpager: freepages found %ud free\n", pa->freecount);
 		goto Done;
 	}
 
@@ -312,8 +293,6 @@
 Done:
 	poperror();
 	qunlock(&pagerlck);
-	if(DBGFLG>1)
-		DBG("kickpager() done %#p\n", up);
 }
 
 void