linux-kernel - Re: [PATCH] mm : bail out from psi memstall after submit_bio in swap

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Message-ID: <79c08d1d-eef5-bc15-8186-7e3367b4ebe7@suse.cz>
Date:   Tue, 7 Sep 2021 14:02:59 +0200
From:   Vlastimil Babka <vbabka@...e.cz>
To:     Huangzhaoyang <huangzhaoyang@...il.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Minchan Kim <minchan@...nel.org>,
        Zhaoyang Huang <zhaoyang.huang@...soc.com>, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org, Johannes Weiner <hannes@...xchg.org>
Subject: Re: [PATCH] mm : bail out from psi memstall after submit_bio in
 swap_readpage

On 9/7/21 13:59, Huangzhaoyang wrote:
> From: Zhaoyang Huang <zhaoyang.huang@...soc.com>
> 
> It doesn't make sense to count IO time into psi memstall. Bail out after
> bio submitted.

Isn't that the point if psi, to observe real stalls, which include IO?
Anyway, CCing Johannes.

> Signed-off-by: Zhaoyang Huang <zhaoyang.huang@...soc.com>
> ---
>  mm/page_io.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/mm/page_io.c b/mm/page_io.c
> index c493ce9..1d131fc 100644
> --- a/mm/page_io.c
> +++ b/mm/page_io.c
> @@ -423,6 +423,7 @@ int swap_readpage(struct page *page, bool synchronous)
>  	count_vm_event(PSWPIN);
>  	bio_get(bio);
>  	qc = submit_bio(bio);
> +	psi_memstall_leave(&pflags);
>  	while (synchronous) {
>  		set_current_state(TASK_UNINTERRUPTIBLE);
>  		if (!READ_ONCE(bio->bi_private))
> @@ -433,7 +434,7 @@ int swap_readpage(struct page *page, bool synchronous)
>  	}
>  	__set_current_state(TASK_RUNNING);
>  	bio_put(bio);
> -
> +	return ret;
>  out:
>  	psi_memstall_leave(&pflags);
>  	return ret;
>