linux-kernel - Re: [RFC PATCH 0/3] Cgroup-based THP control

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Message-ID: <ZyJLFv8TgoTyo5SH@tiehlicka>
Date: Wed, 30 Oct 2024 16:04:54 +0100
From: Michal Hocko <mhocko@...e.com>
To: Chris Down <chris@...isdown.name>
Cc: gutierrez.asier@...wei-partners.com, akpm@...ux-foundation.org,
	david@...hat.com, ryan.roberts@....com, baohua@...nel.org,
	willy@...radead.org, peterx@...hat.com, hannes@...xchg.org,
	hocko@...nel.org, roman.gushchin@...ux.dev, shakeel.butt@...ux.dev,
	muchun.song@...ux.dev, cgroups@...r.kernel.org, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org, stepanov.anatoly@...wei.com,
	alexander.kozhevnikov@...wei-partners.com, guohanjun@...wei.com,
	weiyongjun1@...wei.com, wangkefeng.wang@...wei.com,
	judy.chenhui@...wei.com, yusongping@...wei.com,
	artem.kuzin@...wei.com, kang.sun@...wei.com
Subject: Re: [RFC PATCH 0/3] Cgroup-based THP control

On Wed 30-10-24 14:45:24, Chris Down wrote:
> gutierrez.asier@...wei-partners.com writes:
> > New memcg files are exposed: memory.thp_enabled and memory.thp_defrag, which
> > have completely the same format as global THP enabled/defrag.
> 
> cgroup controls exist because there are things we want to do for an entire
> class of processes (group OOM, resource control, etc). Enabling or disabling
> some specific setting is generally not one of them, hence why we got rid of
> things like per-cgroup vm.swappiness. We know that these controls do not
> compose well and have caused a lot of pain in the past. So my immediate
> reaction is a nack on the general concept, unless there's some absolutely
> compelling case here.
> 
> I talked a little at Kernel Recipes last year about moving away from sysctl
> and other global interfaces and making things more granular. Don't get me
> wrong, I think that is a good thing (although, of course, a very large
> undertaking) -- but it is a mistake to overload the amount of controls we
> expose as part of the cgroup interface.

Completely agreed!

-- 
Michal Hocko
SUSE Labs