Re: [RFC PATCH 4/5] mm: add page implyreclaim flag

[Matthew Wilcox]

On Sun, Oct 08, 2023 at 05:59:23PM +0800, Lincheng Yang wrote:
> Add implyrecalim flag means that the page is reclaim from the user advise.
> diff --git a/include/linux/page-flags.h b/include/linux/page-flags.h
> index a2c83c0100aa..4a1278851d4b 100644
> --- a/include/linux/page-flags.h
> +++ b/include/linux/page-flags.h
> @@ -138,6 +138,7 @@ enum pageflags {
>  #endif
>  	PG_hot,
>  	PG_cold,
> +	PG_implyreclaim,
>  	__NR_PAGEFLAGS,

Can you do all of this without adding three page flags?  We're really
tight on page flags.  At a minimum, this is going to have to go behind
an ifdef that depends on 64BIT, but it'd be better if we can derive
hot/cold/implyreclaim from existing page flags.  Look at the antics
we go through for PG_young and PG_idle; if we had two page flags free,
we'd spend them on removing the special cases there.