Re: SLUB: Reduce antifrag max order (fwd)

[Mel Gorman <mel@csn.ul.ie>]

Sorry for resend, I didn't add Andy to the cc as intended.

On Sat, 5 May 2007, Christoph Lameter wrote:

> My test systems fails to obtain order 4 allocs after prolonged use.
> So the Antifragmentation patches are unable to guarantee order 4
> blocks after a while (straight compile, edit load).
>

Anti-frag still depends on reclaim to take place and I imagine you have not 
altered min_free_kbytes to keep pages free. Also, I don't think kswapd is 
currently making any effort to keep blocks free at a known desired order 
although I'm cc'ing Andy Whitcroft to confirm. As the kernel gives up easily 
when order > PAGE_ALLOC_COSTLY_ORDER, prehaps you should be using 
PAGE_ALLOC_COSTLY_ORDER instead of DEFAULT_ANTIFRAG_MAX_ORDER for SLUB.

> Reduce the the max order if antifrag measures are detected to 3.
> 
> Signed-off-by: Christoph Lameter <clameter@sgi.com>
> 
> ---
> mm/slub.c |    2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
> 
> Index: slub/mm/slub.c
> ===================================================================
> --- slub.orig/mm/slub.c	2007-05-05 09:19:32.000000000 -0700
> +++ slub/mm/slub.c	2007-05-05 09:22:00.000000000 -0700
> @@ -129,7 +129,7 @@
>  * If antifragmentation methods are in effect then increase the
>  * slab sizes to increase performance
>  */
> -#define DEFAULT_ANTIFRAG_MAX_ORDER 4
> +#define DEFAULT_ANTIFRAG_MAX_ORDER 3
> #define DEFAULT_ANTIFRAG_MIN_OBJECTS 16
> 
> /*
>

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

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