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Date:   Wed, 16 Sep 2020 12:24:52 +0100
From:   Chris Down <chris@chrisdown.name>
To:     zangchunxin@bytedance.com
Cc:     akpm@linux-foundation.org, vbabka@suse.cz, mhocko@suse.com,
        linux-mm@kvack.org, linux-kernel@vger.kernel.org,
        Muchun Song <songmuchun@bytedance.com>
Subject: Re: [PATCH v5] mm/vmscan: add a fatal signals check in drop_slab_node
Message-ID: <20200916112452.GA85476@chrisdown.name>
References: <20200916025359.70203-1-zangchunxin@bytedance.com>
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zangchunxin@bytedance.com writes:
>From: Chunxin Zang <zangchunxin@bytedance.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@bytedance.com>
>Signed-off-by: Muchun Song <songmuchun@bytedance.com>

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