Problem with /proc/sys/vm/lowmem_reserve_ratio

Larry Woodman
2008-02-19T21:38:32Z

balance_pgdat() calls zone_watermark_ok() three times, the first call
passes a zero(0) in as the 4th argument. This 4th argument is the
classzone_idx which is used as the index into the zone->lowmem_reserve[]
array.
Since setup_per_zone_lowmem_reserve()
always sets the zone->lowmem_reserve[0] = 0(because there is nothing
below the DMA zone), zone_watermark_ok() will not consider the
lowmem_reserve pages when zero is passed as the 4th arg. The
4th argument must be "i" or balance_pgdat wont even get into the main loop
when lowmem_reserve_ratio is lowered.

-------------------------------------------------------------------------
--- linux-2.6.24.noarch/mm/vmscan.c.orig 2008-02-13
11:14:55.000000000 -0500
+++ linux-2.6.24.noarch/mm/vmscan.c 2008-02-13 11:15:02.000000000
-0500
@@ -1375,7 +1375,7 @@ loop_again:
continue;

if (!zone_watermark_ok(zone, order,
zone->pages_high,

- 0, 0)) {
+ i, 0)) {
end_zone = i;
break;