linux-kernel - Re: [PATCH v2 09/10] sched/psi: per-cgroup PSI stats disable/re-enable interface

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Message-ID: <20220815132343.GA22640@blackbody.suse.cz>
Date:   Mon, 15 Aug 2022 15:23:43 +0200
From:   Michal Koutný <mkoutny@...e.com>
To:     Johannes Weiner <hannes@...xchg.org>
Cc:     Chengming Zhou <zhouchengming@...edance.com>,
        Tejun Heo <tj@...nel.org>, corbet@....net, surenb@...gle.com,
        mingo@...hat.com, peterz@...radead.org, vincent.guittot@...aro.org,
        dietmar.eggemann@....com, rostedt@...dmis.org, bsegall@...gle.com,
        cgroups@...r.kernel.org, linux-doc@...r.kernel.org,
        linux-kernel@...r.kernel.org, songmuchun@...edance.com
Subject: Re: [PATCH v2 09/10] sched/psi: per-cgroup PSI stats
 disable/re-enable interface

On Wed, Aug 10, 2022 at 11:25:07AM -0400, Johannes Weiner <hannes@...xchg.org> wrote:
> cgroup.pressure.enable sounds good to me too. Or, because it's
> default-enabled and that likely won't change, cgroup.pressure.disable.

Will it not change?

I'd say that user would be interested in particular level or even just
level in subtree for PSI, so the opt-out may result in lots of explicit
disablements (or even watch for cgroups created and disable PSI there)
to get some performance back.

I have two suggestions based on the above:
1) Make the default globally configurable (mount option?)
2) Allow implicit enablement upon trigger creation

WDYT?

Michal