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

[KOSAKI Motohiro]

> From: Andrea Arcangeli <aarcange@xxxxxxxxxx>
> 
> With transparent hugepage support we need compaction for the "defrag" sysfs
> controls to be effective.
> 
> Signed-off-by: Andrea Arcangeli <aarcange@xxxxxxxxxx>
> ---
> 
> 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.



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