linux-kernel - Re: [PATCH v5 1/2] mm/memcontrol.c: try harder to decrease [memory,memsw].limit_in

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Date:   Thu, 25 Jan 2018 22:44:16 +0300
From:   Andrey Ryabinin <aryabinin@...tuozzo.com>
To:     Andrew Morton <akpm@...ux-foundation.org>
Cc:     cgroups@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-mm@...ck.org, Shakeel Butt <shakeelb@...gle.com>,
        Michal Hocko <mhocko@...nel.org>,
        Johannes Weiner <hannes@...xchg.org>,
        Vladimir Davydov <vdavydov.dev@...il.com>
Subject: Re: [PATCH v5 1/2] mm/memcontrol.c: try harder to decrease
 [memory,memsw].limit_in_bytes

On 01/19/2018 04:25 PM, Andrey Ryabinin wrote:
> mem_cgroup_resize_[memsw]_limit() tries to free only 32 (SWAP_CLUSTER_MAX)
> pages on each iteration.  This makes it practically impossible to decrease
> limit of memory cgroup.  Tasks could easily allocate back 32 pages, so we
> can't reduce memory usage, and once retry_count reaches zero we return
> -EBUSY.
> 
> Easy to reproduce the problem by running the following commands:
> 
>   mkdir /sys/fs/cgroup/memory/test
>   echo $$ >> /sys/fs/cgroup/memory/test/tasks
>   cat big_file > /dev/null &
>   sleep 1 && echo $((100*1024*1024)) > /sys/fs/cgroup/memory/test/memory.limit_in_bytes
>   -bash: echo: write error: Device or resource busy
> 
> Instead of relying on retry_count, keep retrying the reclaim until the
> desired limit is reached or fail if the reclaim doesn't make any progress
> or a signal is pending.
> 
> Signed-off-by: Andrey Ryabinin <aryabinin@...tuozzo.com>
> Cc: Shakeel Butt <shakeelb@...gle.com>
> Cc: Michal Hocko <mhocko@...nel.org>
> Cc: Johannes Weiner <hannes@...xchg.org>
> Cc: Vladimir Davydov <vdavydov.dev@...il.com>


Andrew, are you ok to pick up the patch?