linux-kernel - Re: [RFC PATCH V3 5/6] sched/fair: Add trivial fair server

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Date:   Fri, 16 Jun 2023 15:12:43 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Daniel Bristot de Oliveira <bristot@...nel.org>
Cc:     Ingo Molnar <mingo@...hat.com>, Juri Lelli <juri.lelli@...hat.com>,
        Vincent Guittot <vincent.guittot@...aro.org>,
        Dietmar Eggemann <dietmar.eggemann@....com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Ben Segall <bsegall@...gle.com>, Mel Gorman <mgorman@...e.de>,
        Daniel Bristot de Oliveira <bristot@...hat.com>,
        Valentin Schneider <vschneid@...hat.com>,
        linux-kernel@...r.kernel.org,
        Luca Abeni <luca.abeni@...tannapisa.it>,
        Tommaso Cucinotta <tommaso.cucinotta@...tannapisa.it>,
        Thomas Gleixner <tglx@...utronix.de>,
        Joel Fernandes <joel@...lfernandes.org>,
        Vineeth Pillai <vineeth@...byteword.org>,
        Shuah Khan <skhan@...uxfoundation.org>
Subject: Re: [RFC PATCH V3 5/6] sched/fair: Add trivial fair server

On Fri, Jun 16, 2023 at 03:00:57PM +0200, Daniel Bristot de Oliveira wrote:
> On 6/16/23 14:59, Peter Zijlstra wrote:
> > On Thu, Jun 08, 2023 at 05:58:17PM +0200, Daniel Bristot de Oliveira wrote:
> >> +void fair_server_init(struct rq *rq)
> >> +{
> >> +	struct sched_dl_entity *dl_se = &rq->fair_server;
> >> +
> >> +	init_dl_entity(dl_se);
> >> +
> >> +	dl_se->dl_runtime = TICK_NSEC;
> >> +	dl_se->dl_deadline = 20 * TICK_NSEC;
> >> +	dl_se->dl_period = 20 * TICK_NSEC;
> >> +
> >> +	dl_server_init(dl_se, rq, fair_server_has_tasks, fair_server_pick);
> >> +}
> > 
> > These here numbers should obviously become a tunable somewhere... :-)
> 
> From sched_rt_runtime and sched_rt_period, no?

Well, probably new names. IIRC those are also limits on the whole
rt-cgroup mess, so e can't trivially change it without also ripping all
that out, and that's a little bit more work.

Ripping out the basic throttle is much simpler than replacing all that
and should be done earlier.