linux-kernel - Re: [PATCH] mm/memcg: support control THP behaviour in cgroup

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Date:   Sat, 7 May 2022 02:05:25 +0000
From:   CGEL <cgel.zte@...il.com>
To:     Michal Hocko <mhocko@...e.com>
Cc:     akpm@...ux-foundation.org, hannes@...xchg.org, willy@...radead.org,
        shy828301@...il.com, roman.gushchin@...ux.dev, shakeelb@...gle.com,
        linmiaohe@...wei.com, william.kucharski@...cle.com,
        peterx@...hat.com, hughd@...gle.com, vbabka@...e.cz,
        songmuchun@...edance.com, surenb@...gle.com,
        linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        cgroups@...r.kernel.org, Yang Yang <yang.yang29@....com.cn>
Subject: Re: [PATCH] mm/memcg: support control THP behaviour in cgroup

On Fri, May 06, 2022 at 03:41:50PM +0200, Michal Hocko wrote:
> On Thu 05-05-22 03:38:15, cgel.zte@...il.com wrote:
> > From: Yang Yang <yang.yang29@....com.cn> 
> > 
> > Using THP may promote the performance of memory, but increase memory
> > footprint. Applications may use madvise to decrease footprint, but
> > not all applications support using madvise, and it takes much costs
> > to re-code all the applications. And we notice container becomes more
> > and more popular to manage a set of tasks.
> 
> Could you be more specific about the actual usecase? When do you group
> processes based on their general THP reqirements? You are mentioning
> containers but those are usually bags of different processes that just
> share a common objective.
>
> > So add support for cgroup to control THP behaviour will provide much
> > convenience, administrator may only enable THP for important containers,
> > and disable it for other containers.
> 
> Why would that be a matter of importance?
> 
> Also what is actual semantic when processes living inside those cgroups
> explicitly state their THP requirements?
>
Docker might support this new cgroup knob in the future, add provide UI likes:
# docker run -it --thp-enabled=[always,never,madvise]
The cmdline format from https://docs.docker.com/engine/reference/run/

If there are many containers to run on one host, and some of them have high
performance requirements, administrator could turn on thp for them:
# docker run -it --thp-enabled=always
Then all the processes in those containers will always use thp.
While other containers turn off thp by:
# docker run -it --thp-enabled=never

By doing this we could promote important containers's performance with less
footprint of thp.
> -- 
> Michal Hocko
> SUSE Labs