[PATCH] powerpc: Set a smaller value for RECLAIM_DISTANCE to enable zone reclaim

[Balbir Singh]

On Fri, Feb 19, 2010 at 3:59 AM, Anton Blanchard <anton at samba.org> wrote:
>
> 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.
>

A reclaim distance of 10 implies a ratio of 1, that means we'll always
do zone_reclaim() to free page cache and slab cache before moving on
to another node?

Balbir Singh.