From: Anton Blanchard <anton@samba.org>
Date: Thu, 18 Feb 2010 12:29:23 +0000 (+0000)
Subject: powerpc/numa: Set a smaller value for RECLAIM_DISTANCE to enable zone reclaim
X-Git-Tag: v2.6.35-rc1~450^2~69
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=27f10907b7cca57df5e2a9c94c14354dd1b7879d;p=pandora-kernel.git

powerpc/numa: Set a smaller value for RECLAIM_DISTANCE to enable zone reclaim

I noticed /proc/sys/vm/zone_reclaim_mode was 0 on a ppc64 NUMA box. It gets
enabled via this:

        /*
         * If another node is sufficiently far away then it is better
         * to reclaim pages in a zone before going off node.
         */
        if (distance > RECLAIM_DISTANCE)
                zone_reclaim_mode = 1;

Since we use the default value of 20 for REMOTE_DISTANCE and 20 for
RECLAIM_DISTANCE it never kicks in.

The local to remote bandwidth ratios can be quite large on System p
machines so it makes sense for us to reclaim clean pagecache locally before
going off node.

The patch below sets a smaller value for RECLAIM_DISTANCE and thus enables
zone reclaim.

Signed-off-by: Anton Blanchard <anton@samba.org>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
---

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