linux-kernel - Re: [RFC PROPOSAL] memcg: per-memcg user space reclaim interface

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Message-ID: <20200703063548.GM18446@dhcp22.suse.cz>
Date:   Fri, 3 Jul 2020 08:35:48 +0200
From:   Michal Hocko <mhocko@...nel.org>
To:     Shakeel Butt <shakeelb@...gle.com>
Cc:     Johannes Weiner <hannes@...xchg.org>, Roman Gushchin <guro@...com>,
        Yang Shi <yang.shi@...ux.alibaba.com>,
        David Rientjes <rientjes@...gle.com>,
        Greg Thelen <gthelen@...gle.com>,
        Andrew Morton <akpm@...ux-foundation.org>, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org, cgroups@...r.kernel.org
Subject: Re: [RFC PROPOSAL] memcg: per-memcg user space reclaim interface

On Thu 02-07-20 08:22:22, Shakeel Butt wrote:
[...]
> Interface options:
> ------------------
> 
> 1) memcg interface e.g. 'echo 10M > memory.reclaim'
> 
> + simple
> + can be extended to target specific type of memory (anon, file, kmem).
> - most probably restricted to cgroup v2.
> 
> 2) fadvise(PAGEOUT) on cgroup_dir_fd
> 
> + more general and applicable to other FSes (actually we are using
> something similar for tmpfs).
> + can be extended in future to just age the LRUs instead of reclaim or
> some new use cases.

Could you explain why memory.high as an interface to trigger pro-active
memory reclaim is not sufficient. Also memory.low limit to protect
latency sensitve workloads?
-- 
Michal Hocko
SUSE Labs