linux-kernel - Re: [PATCH 3/5] mm:swap: introduce SWP_SYNCHRONOUS

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Date:   Tue, 12 Sep 2017 13:48:03 +0900
From:   Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>
To:     Minchan Kim <minchan@...nel.org>
Cc:     Andrew Morton <akpm@...ux-foundation.org>, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org, kernel-team <kernel-team@....com>,
        Ilya Dryomov <idryomov@...il.com>,
        Sergey Senozhatsky <sergey.senozhatsky@...il.com>
Subject: Re: [PATCH 3/5] mm:swap: introduce SWP_SYNCHRONOUS_IO

On (09/12/17 11:37), Minchan Kim wrote:
[..]
> If rw-page based fast storage is used for swap devices, we need to
> detect it to enhance swap IO operations.
> This patch is preparation for optimizing of swap-in operation with
> next patch.
> 
> Signed-off-by: Minchan Kim <minchan@...nel.org>
> ---
>  include/linux/swap.h | 3 ++-
>  mm/swapfile.c        | 3 +++
>  2 files changed, 5 insertions(+), 1 deletion(-)
> 
> diff --git a/include/linux/swap.h b/include/linux/swap.h
> index 8a807292037f..0f54b491e118 100644
> --- a/include/linux/swap.h
> +++ b/include/linux/swap.h
> @@ -170,8 +170,9 @@ enum {
>  	SWP_AREA_DISCARD = (1 << 8),	/* single-time swap area discards */
>  	SWP_PAGE_DISCARD = (1 << 9),	/* freed swap page-cluster discards */
>  	SWP_STABLE_WRITES = (1 << 10),	/* no overwrite PG_writeback pages */
> +	SWP_SYNCHRONOUS_IO = (1<<11),	/* synchronous IO is efficient */
a nitpick:                  (1 << 11)

	-ss

>  					/* add others here before... */
> -	SWP_SCANNING	= (1 << 11),	/* refcount in scan_swap_map */
> +	SWP_SCANNING	= (1 << 12),	/* refcount in scan_swap_map */
>  };