linux-kernel - Re: [PATCH] sched/deadline: Add DL server activated message

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Message-ID: <aJRSmWCJI-GlApsR@jlelli-thinkpadt14gen4.remote.csb>
Date: Thu, 7 Aug 2025 08:15:37 +0100
From: Juri Lelli <juri.lelli@...hat.com>
To: Kuyo Chang <kuyo.chang@...iatek.com>
Cc: Ingo Molnar <mingo@...hat.com>, Peter Zijlstra <peterz@...radead.org>,
	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>,
	Matthias Brugger <matthias.bgg@...il.com>,
	AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>,
	linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
	linux-mediatek@...ts.infradead.org
Subject: Re: [PATCH] sched/deadline: Add DL server activated message

Hi,

On 05/08/25 23:53, Kuyo Chang wrote:
> From: kuyo chang <kuyo.chang@...iatek.com>
> 
> The DL server is introduced as a replacement for realtime throttling.
> When RT throttling is activated, a message
> "sched: RT throttling activated" is shown. However, it is currently
> difficult for users to know when the DL server is activated.
> 
> This patch adds a similar message to indicate when the DL server
> is activated, which helps users debug RT/CFS contention issues.
> 
> Signed-off-by: kuyo chang <kuyo.chang@...iatek.com>
> ---
>  kernel/sched/deadline.c | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c
> index e2d51f4306b3..8e0de6cdb980 100644
> --- a/kernel/sched/deadline.c
> +++ b/kernel/sched/deadline.c
> @@ -2042,6 +2042,9 @@ enqueue_dl_entity(struct sched_dl_entity *dl_se, int flags)
>  	}
>  
>  	__enqueue_dl_entity(dl_se);
> +
> +	if (dl_server(dl_se))
> +		printk_deferred_once("sched: dl_server activated\n");
>  }

Not sure if we want/need this, but, if we do, I believe
fair_server_pick_task() might be a better place to put it, as it's
really when the dl-server is called to do its job.

Thanks,
Juri