linux-kernel - Re: [PATCH v5 5/7] sched/fair: Add trivial fair server

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Message-ID: <20231106142430.GF3818@noisy.programming.kicks-ass.net>
Date:   Mon, 6 Nov 2023 15:24:30 +0100
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>,
        Phil Auld <pauld@...hat.com>
Subject: Re: [PATCH v5 5/7] sched/fair: Add trivial fair server

On Sat, Nov 04, 2023 at 11:59:22AM +0100, Daniel Bristot de Oliveira wrote:

> [ dl_server do not account for rt ]

> diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c
> index 541d547e1019..1d7b96ca9011 100644
> --- a/kernel/sched/deadline.c
> +++ b/kernel/sched/deadline.c
> @@ -1382,6 +1382,13 @@ static void update_curr_dl_se(struct rq *rq, struct sched_dl_entity *dl_se, s64
>  			resched_curr(rq);
>  	}
>  
> +	/*
> +	 * The fair server (sole dl_server) does not account for real-time
> +	 * workload because it is running fair work.
> +	 */
> +	if (dl_server(dl_se))
> +		return;
> +
>  	/*
>  	 * Because -- for now -- we share the rt bandwidth, we need to
>  	 * account our runtime there too, otherwise actual rt tasks

Should we perhaps write this like so?

	if (dl_se == &rq->fair_server)
		return;