Re: kswapd in tight loop 2.6.9-rc3-bk-recent

[Nick Piggin <nickpiggin@yahoo.com.au>]

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Nick Piggin wrote:

> 
> I think my patch would be sufficient to handle the kswapd side
> (yours would be valid too, but no need to add the extra checks).

Here is the combined patch with Andrew's hunk added.

I guess it doesn't _really_ matter which gets tested, but this
one is probably the preferred way to go because it doesn't even
wake up kswapd for empty zones. Andrew, do you agree?

I guess it should get into -bk pretty soon if it passes testing.
It is fairly easy to see the failure cases that are fixed (and
hopefully it doesn't domino yet another latent bug :P).

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Signed-off-by: Nick Piggin <nickpiggin@yahoo.com.au>


---

 linux-2.6-npiggin/mm/vmscan.c |    9 ++++++---
 1 files changed, 6 insertions(+), 3 deletions(-)

diff -puN mm/vmscan.c~vm-fix-empty-zones mm/vmscan.c
--- linux-2.6/mm/vmscan.c~vm-fix-empty-zones	2004-10-08 12:44:14.000000000 +1000
+++ linux-2.6-npiggin/mm/vmscan.c	2004-10-08 14:28:04.000000000 +1000
@@ -851,6 +851,9 @@ shrink_caches(struct zone **zones, struc
 	for (i = 0; zones[i] != NULL; i++) {
 		struct zone *zone = zones[i];
 
+		if (zone->present_pages == 0)
+			continue;
+
 		zone->temp_priority = sc->priority;
 		if (zone->prev_priority > sc->priority)
 			zone->prev_priority = sc->priority;
@@ -1003,7 +1006,7 @@ static int balance_pgdat(pg_data_t *pgda
 						priority != DEF_PRIORITY)
 					continue;
 
-				if (zone->free_pages <= zone->pages_high) {
+				if (zone->free_pages < zone->pages_high) {
 					end_zone = i;
 					goto scan;
 				}
@@ -1035,7 +1038,7 @@ scan:
 				continue;
 
 			if (nr_pages == 0) {	/* Not software suspend */
-				if (zone->free_pages <= zone->pages_high)
+				if (zone->free_pages < zone->pages_high)
 					all_zones_ok = 0;
 			}
 			zone->temp_priority = priority;
@@ -1142,7 +1145,7 @@ static int kswapd(void *p)
  */
 void wakeup_kswapd(struct zone *zone)
 {
-	if (zone->free_pages > zone->pages_low)
+	if (zone->free_pages >= zone->pages_low)
 		return;
 	if (!waitqueue_active(&zone->zone_pgdat->kswapd_wait))
 		return;

_