linux-kernel - Re: [PATCH v2 2/2] mm/page_io: count submission time as thrashing delay for delayacct

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Date:   Wed, 14 Sep 2022 23:49:35 +0900
From:   Joonsoo Kim <js1304@...il.com>
To:     cgel.zte@...il.com
Cc:     akpm@...ux-foundation.org, iamjoonsoo.kim@....com,
        linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        Yang Yang <yang.yang29@....com.cn>,
        Ran Xiaokai <ran.xiaokai@....com.cn>,
        wangyong <wang.yong12@....com.cn>
Subject: Re: [PATCH v2 2/2] mm/page_io: count submission time as thrashing
 delay for delayacct

2022년 8월 15일 (월) 오후 4:33, <cgel.zte@...il.com>님이 작성:
>
> From: Yang Yang <yang.yang29@....com.cn>
>
> Once upon a time, we only support accounting thrashing of page cache.
> Then Joonsoo introduced workingset detection for anonymous pages and
> we gained the ability to account thrashing of them[1].
>
> Likes PSI, we count submission time as thrashing delay because when
> the device is congested, or the submitting cgroup IO-throttled,
> submission can be a significant part of overall IO time.

It's not the main purpose of this patch. Without this patch,
swap thrashing through frontswap or some block device supporting rw_page
operation isn't measured correctly. I think that description change is
required. Please refer to commit 937790699be9c8100e
(mm/page_io.c: annotate refault stalls from swap_readpage).

No objection on the code side.

Thanks.