Re: [PATCH 04/14] Allow CONFIG_MIGRATION to be set withoutCONFIG_NUMA or memory hot-remove

[Andrew Morton]

On Fri,  2 Apr 2010 17:02:38 +0100
Mel Gorman <mel@xxxxxxxxx> wrote:

> CONFIG_MIGRATION currently depends on CONFIG_NUMA or on the architecture
> being able to hot-remove memory. The main users of page migration such as
> sys_move_pages(), sys_migrate_pages() and cpuset process migration are
> only beneficial on NUMA so it makes sense.
> 
> As memory compaction will operate within a zone and is useful on both NUMA
> and non-NUMA systems, this patch allows CONFIG_MIGRATION to be set if the
> user selects CONFIG_COMPACTION as an option.
> 
> ...
>
> --- a/mm/Kconfig
> +++ b/mm/Kconfig
> @@ -172,6 +172,16 @@ config SPLIT_PTLOCK_CPUS
>  	default "4"
>  
>  #
> +# support for memory compaction
> +config COMPACTION
> +	bool "Allow for memory compaction"
> +	def_bool y
> +	select MIGRATION
> +	depends on EXPERIMENTAL && HUGETLBFS && MMU
> +	help
> +	  Allows the compaction of memory for the allocation of huge pages.

Seems strange to depend on hugetlbfs.  Perhaps depending on
HUGETLB_PAGE would be more logical.

But hang on.  I wanna use compaction to make my order-4 wireless skb
allocations work better!  Why do you hate me?


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