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SubjectRe: [PATCH] Do not clobber pgdat->nr_zones during memory initialisation
On (03/07/08 09:44), Linus Torvalds didst pronounce:
>
>
> On Thu, 3 Jul 2008, Mel Gorman wrote:
> >
> > Subject: [PATCH] Do not clobber pgdat->nr_zones during memory initialisation
>
> Heh. I already applied it as ObviouslyCorrect(tm), but did the
> simplification I already pointed out (and which your second version
> already had) and rewrote your commit message a bit. So it's now committed
> as follows..
>

Perfect. The log even looks like it was written by a sane person. Thanks
for that.

> Linus
>
> ---
> commit 494de90098784b8e2797598cefdd34188884ec2e
> Author: Mel Gorman <mel@csn.ul.ie>
> Date: Thu Jul 3 05:27:51 2008 +0100
>
> Do not overwrite nr_zones on !NUMA when initialising zlcache_ptr
>
> The non-NUMA case of build_zonelist_cache() would initialize the
> zlcache_ptr for both node_zonelists[] to NULL.
>
> Which is problematic, since non-NUMA only has a single node_zonelists[]
> entry, and trying to zero the non-existent second one just overwrote the
> nr_zones field instead.
>
> As kswapd uses this value to determine what reclaim work is necessary,
> the result is that kswapd never reclaims. This causes processes to
> stall frequently in low-memory situations as they always direct reclaim.
> This patch initialises zlcache_ptr correctly.
>
> Signed-off-by: Mel Gorman <mel@csn.ul.ie>
> Tested-by: Dan Williams <dan.j.williams@intel.com>
> [ Simplified patch a bit ]
> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
> ---
> mm/page_alloc.c | 1 -
> 1 files changed, 0 insertions(+), 1 deletions(-)
>
> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> index 2f55295..f32fae3 100644
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -2328,7 +2328,6 @@ static void build_zonelists(pg_data_t *pgdat)
> static void build_zonelist_cache(pg_data_t *pgdat)
> {
> pgdat->node_zonelists[0].zlcache_ptr = NULL;
> - pgdat->node_zonelists[1].zlcache_ptr = NULL;
> }
>
> #endif /* CONFIG_NUMA */
>

--
Mel Gorman
Part-time Phd Student Linux Technology Center
University of Limerick IBM Dublin Software Lab


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