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From:   Vincent Guittot <vincent.guittot@linaro.org>
Date:   Tue, 28 Feb 2023 10:09:47 +0100
Message-ID: <CAKfTPtAq-fRhgXw21RxLhT_ZZQUoMSZgGc90R_qoqkUhu+ADDw@mail.gmail.com>
Subject: Re: [PATCH v12 6/8] sched/fair: Add sched group latency support
To:     =?UTF-8?Q?Michal_Koutn=C3=BD?= <mkoutny@suse.com>
Cc:     mingo@redhat.com, peterz@infradead.org, juri.lelli@redhat.com,
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On Mon, 27 Feb 2023 at 15:42, Michal Koutn=C3=BD <mkoutny@suse.com> wrote:
>
> On Mon, Feb 27, 2023 at 02:44:22PM +0100, Vincent Guittot <vincent.guitto=
t@linaro.org> wrote:
> > Regarding the current use of latency nice to set a latency offset, the
> > problem doesn't appear because latency offset applies between entities
> > at the same level as you mentioned above
>
> Splendid, it turned out that way (latency nice analogous to bandwidth
> nice).
>
> > Does  my explanation above make sense to you ?
>
> Yes, thank you.
>
> Thus, I'd like to propose avoiding the use of "limit" in this context and
> stress the horizontal scope. For example:
>
> > +     This interface file allows reading and setting latency using the
> > +     same values used by sched_setattr(2). The latency_nice of a group=
 is
> > +     used to limit the impact of the latency_nice of a task outside th=
e
> > +     group.
>
> +     This interface file allows reading and setting latency using the
> +     same values used by sched_setattr(2). The latency_nice of a group i=
s
> +     used to modify group members' latency with respect to sibling group=
s.

That sounds reasonable to me.

>
> Regards,
> Michal