linux-kernel - Problem with /proc/sys/vm/lowmem_reserve

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Message-ID: <47BB4BB5.20709@redhat.com>
Date:	Tue, 19 Feb 2008 16:35:49 -0500
From:	Larry Woodman <lwoodman@...hat.com>
To:	linux-kernel@...r.kernel.org,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Problem with /proc/sys/vm/lowmem_reserve_ratio

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;

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