From d0b1db98bcade0335b7762cb76e236a483143f91 Mon Sep 17 00:00:00 2001
From: cinap_lenrek <cinap_lenrek@felloff.net>
Date: Mon, 16 Mar 2015 05:23:38 +0100
Subject: [PATCH] kernel: avoid repeated calls to reclaim(), dont miss last
 page in Pte

when we are skipping a process because we could not acquire
its segment lock, dont call reclaim() again (which is pointless
as we didnt pageout any pages), instead try the next process.

the Pte.last pointer is inclusive, so don't miss the last page
in pageout().
---
 sys/src/9/port/swap.c | 28 ++++++++++++----------------
 1 file changed, 12 insertions(+), 16 deletions(-)

diff --git a/sys/src/9/port/swap.c b/sys/src/9/port/swap.c
index 355c37f5f..bc763acf1 100644
--- a/sys/src/9/port/swap.c
+++ b/sys/src/9/port/swap.c
@@ -7,7 +7,6 @@
 
 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*);
@@ -166,24 +165,21 @@ pager(void*)
 		}
 
 		if(swapimage.c == nil || swapalloc.free == 0){
+		Killbig:
 			killbig("out of memory");
 			freebroken();		/* can use the memory */
 			sched();
 			continue;
 		}
 
-		p++;
-		if(p >= ep){
-			p = proctab(0);
-			ageclock++;
-		}
-
-		if(p->state == Dead || p->noswap)
-			continue;
-
-		if(!canqlock(&p->seglock))
-			continue;		/* process changing its segments */
-
+		i = ageclock;
+		do {
+			if(++p >= ep){
+				if(++ageclock == i)
+					goto Killbig;
+				p = proctab(0);
+			}
+		} while(p->state == Dead || p->noswap || !canqlock(&p->seglock));
 		up->psstate = "Pageout";
 		for(i = 0; i < NSEG; i++) {
 			if((s = p->seg[i]) != nil) {
@@ -239,9 +235,9 @@ pageout(Proc *p, Segment *s)
 	size = s->mapsize;
 	for(i = 0; i < size; i++) {
 		l = s->map[i];
-		if(l == 0)
+		if(l == nil)
 			continue;
-		for(pg = l->first; pg < l->last; pg++) {
+		for(pg = l->first; pg <= l->last; pg++) {
 			entry = *pg;
 			if(pagedout(entry))
 				continue;
@@ -389,7 +385,7 @@ executeio(void)
 	ioptr = 0;
 }
 
-static int
+int
 needpages(void*)
 {
 	return palloc.freecount < swapalloc.headroom;