linux-kernel - Re: [PATCH v2] sched/deadline: Remove fair-servers from real-time task's bandwidth accounting

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Message-ID: <094f8017f1d9a76ced80e75168de4cd3@codethink.co.uk>
Date: Fri, 25 Jul 2025 20:04:45 +0200
From: Matteo Martelli <matteo.martelli@...ethink.co.uk>
To: Yuri Andriaccio <yurand2000@...il.com>
Cc: linux-kernel@...r.kernel.org, Luca Abeni <luca.abeni@...tannapisa.it>,
	Yuri Andriaccio <yuri.andriaccio@...tannapisa.it>, Ingo Molnar <mingo@...hat.com>,
	Peter Zijlstra <peterz@...radead.org>, 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>, Valentin Schneider
	<vschneid@...hat.com>, Matteo Martelli <matteo.martelli@...ethink.co.uk>
Subject: Re: [PATCH v2] sched/deadline: Remove fair-servers from real-time
 task's bandwidth accounting

Hi Yuri,

On Fri, 25 Jul 2025 18:44:12 +0200, Yuri Andriaccio <yurand2000@...il.com> wrote:
> ...
> @@ -1688,17 +1690,14 @@ int dl_server_apply_params(struct sched_dl_entity *dl_se, u64 runtime, u64 perio
>
>	cpus = dl_bw_cpus(cpu);
>	cap = dl_bw_capacity(cpu);
> +	max_bw = div64_ul(cap_scale(BW_UNIT - dl_b->bw, cap), (unsigned long)cpus);

This line exceeds 80 characters width. Perhaps it needs to be split.

> 
> -	if (__dl_overflow(dl_b, cap, old_bw, new_bw))
> +	if (new_bw > max_bw)
> 		return -EBUSY;
> ...

Beside that minor note, I retested the v2 of this patch with the same
tests I ran for v1 [1]. I confirm that stress-ng and runtime variations
commands provide the same results. Also no warning is produced anymore
as I also applied Juri's patch as you suggested [2].

Tested-by: Matteo Martelli <matteo.martelli@...ethink.co.uk>

[1]: https://lore.kernel.org/all/86013fcc38e582ab89b9b7e4864cc1bd@codethink.co.uk/
[2]: https://lore.kernel.org/all/20250725152804.14224-1-yurand2000@gmail.com/