linux-kernel - Re: [PATCH] sched/debug: Print slice length for fair tasks

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Message-ID: <659b272b-b27e-44a8-b8dd-a6821c1daeba@arm.com>
Date: Wed, 29 Jan 2025 18:04:48 +0000
From: Christian Loehle <christian.loehle@....com>
To: "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
 Peter Zijlstra <peterz@...radead.org>
Cc: Ingo Molnar <mingo@...hat.com>, Juri Lelli <juri.lelli@...hat.com>,
 Steven Rostedt <rostedt@...dmis.org>,
 Vincent Guittot <vincent.guittot@...aro.org>,
 Valentin Schneider <vschneid@...hat.com>,
 Petre-Ionut Tudor <petre-ionut.tudor@....com>
Subject: Re: [PATCH] sched/debug: Print slice length for fair tasks

On 1/29/25 17:59, Christian Loehle wrote:
> With commit 857b158dc5e8 ("sched/eevdf: Use sched_attr::sched_runtime
> to set request/slice suggestion") we have the userspace per-task tunable
> slice length so print it in /proc/$PID/sched.
> 
> Signed-off-by: Christian Loehle <christian.loehle@....com>
> ---
>  kernel/sched/debug.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/kernel/sched/debug.c b/kernel/sched/debug.c
> index fd7e85220715..ef047add7f9e 100644
> --- a/kernel/sched/debug.c
> +++ b/kernel/sched/debug.c
> @@ -1262,6 +1262,8 @@ void proc_sched_show_task(struct task_struct *p, struct pid_namespace *ns,
>  	if (task_has_dl_policy(p)) {
>  		P(dl.runtime);
>  		P(dl.deadline);
> +	} else if (fair_policy(p->policy)) {
> +		P(se.slice);
>  	}
>  #ifdef CONFIG_SCHED_CLASS_EXT
>  	__PS("ext.enabled", task_on_scx(p));

So Peter added a debug slice length print for all tasks on
the rq in commit ("147f3efaa241 sched/fair: Implement an EEVDF-like
scheduling policy") already, but that alone is a bit awkward to play
with when modifying slice length for specific tasks which aren't
always enqueued.