linux-kernel - Re: [PATCH v5] mm/vmscan: add a fatal signals check in drop_slab

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Message-ID: <20200916112452.GA85476@chrisdown.name>
Date:   Wed, 16 Sep 2020 12:24:52 +0100
From:   Chris Down <chris@...isdown.name>
To:     zangchunxin@...edance.com
Cc:     akpm@...ux-foundation.org, vbabka@...e.cz, mhocko@...e.com,
        linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        Muchun Song <songmuchun@...edance.com>
Subject: Re: [PATCH v5] mm/vmscan: add a fatal signals check in drop_slab_node

zangchunxin@...edance.com writes:
>From: Chunxin Zang <zangchunxin@...edance.com>
>
>On our server, there are about 10k memcg in one machine. They use memory
>very frequently. We have observed that drop_caches can take a
>considerable amount of time, and can't stop it.
>
>There are two reasons:
>1. There is somebody constantly generating more objects to reclaim
>  on drop_caches, result the 'freed' always bigger than 10.
>2. The process has no chance to process signals.
>
>We can get the following info through 'ps':
>
> root:~# ps -aux | grep drop
> root  357956 ... R    Aug25 21119854:55 echo 3 > /proc/sys/vm/drop_caches
> root 1771385 ... R    Aug16 21146421:17 echo 3 > /proc/sys/vm/drop_caches
>
>Add a bail out on the fatal signals in the main loop so that the
>operation can be terminated by userspace.
>
>Signed-off-by: Chunxin Zang <zangchunxin@...edance.com>
>Signed-off-by: Muchun Song <songmuchun@...edance.com>

Acked-by: Chris Down <chris@...isdown.name>