linux-kernel - Re: [RFC] memcg v1: provide read access to memory.pressure

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Message-ID: <ZCH/RVlh1M6DRXaU@dhcp22.suse.cz>
Date:   Mon, 27 Mar 2023 22:40:37 +0200
From:   Michal Hocko <mhocko@...e.com>
To:     Florian Schmidt <flosch@...anix.com>
Cc:     Michal Koutný <mkoutny@...e.com>,
        Johannes Weiner <hannes@...xchg.org>,
        Roman Gushchin <roman.gushchin@...ux.dev>,
        Shakeel Butt <shakeelb@...gle.com>,
        Muchun Song <muchun.song@...ux.dev>,
        Andrew Morton <akpm@...ux-foundation.org>,
        cgroups@...r.kernel.org, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Subject: Re: [RFC] memcg v1: provide read access to memory.pressure_level

On Mon 27-03-23 14:59:37, Florian Schmidt wrote:
> Hi Michal,
> 
> On 24/03/2023 15:03, Michal Koutný wrote:
> > On Wed, Mar 22, 2023 at 02:25:25PM +0000, Florian Schmidt <flosch@...anix.com> wrote:
[...]
> > > (b) would you be interested to take this patch, or is it too niche a fix
> > >      for a legacy subsystem?
> > 
> > I'd rather not extend this "unique way" with additionally unique dummy
> > helpers.
> 
> I understand that this is all code that has no modern user any more, which
> is why I tried to keep the fix as self-contained as possible.
> Another option would be to have a special handler in cgroup_file_mode(), but
> that feels a lot klunkier to me, and leaks a v1-specific behaviour into the
> shared cgroup code.

Yes, this is effectivelly a deprecated interface but I do agree that we
shouldn't really make life of users more complicated than necessary. If
the simplest solution to address this is to provide an empty callback
then be it. I am not sure but I do not think there are other cgroup
interfaces to warrant a more generic solution.

-- 
Michal Hocko
SUSE Labs