Re: [PATCH 55 of 66] select CONFIG_COMPACTION if TRANSPARENT_HUGEPAGE enabled

KOSAKI Motohiro
2010-11-09T06:20:41Z

> From: Andrea Arcangeli <aarcange@redhat.com>
>
> With transparent hugepage support we need compaction for the "defrag" sysfs
> controls to be effective.
>
> Signed-off-by: Andrea Arcangeli <aarcange@redhat.com>
> ---
>
> diff --git a/mm/Kconfig b/mm/Kconfig
> --- a/mm/Kconfig
> +++ b/mm/Kconfig
> @@ -305,6 +305,7 @@ config NOMMU_INITIAL_TRIM_EXCESS
> config TRANSPARENT_HUGEPAGE
> bool "Transparent Hugepage Support"
> depends on X86 && MMU
> + select COMPACTION
> help
> Transparent Hugepages allows the kernel to use huge pages and
> huge tlb transparently to the applications whenever possible.

I dislike this. THP and compaction are completely orthogonal. I think
you are talking only your performance recommendation. I mean I dislike
Kconfig 'select' hell and I hope every developers try to avoid it as
far as possible.

Thanks.