linux-kernel - Re: [PATCH v2] sched/rt: Clean up usage of rt

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Message-ID: <20240531063016.OCMg21Uq@linutronix.de>
Date: Fri, 31 May 2024 08:30:16 +0200
From: Sebastian Andrzej Siewior <bigeasy@...utronix.de>
To: Qais Yousef <qyousef@...alina.io>
Cc: Ingo Molnar <mingo@...nel.org>, Peter Zijlstra <peterz@...radead.org>,
	Juri Lelli <juri.lelli@...hat.com>,
	Steven Rostedt <rostedt@...dmis.org>,
	Vincent Guittot <vincent.guittot@...aro.org>,
	Daniel Bristot de Oliveira <bristot@...hat.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Alexander Viro <viro@...iv.linux.org.uk>,
	Christian Brauner <brauner@...nel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Jens Axboe <axboe@...nel.dk>, linux-kernel@...r.kernel.org,
	linux-fsdevel@...r.kernel.org, linux-trace-kernel@...r.kernel.org,
	linux-mm@...ck.org, Phil Auld <pauld@...hat.com>
Subject: Re: [PATCH v2] sched/rt: Clean up usage of rt_task()

On 2024-05-30 12:10:44 [+0100], Qais Yousef wrote:
> > This is not consistent because IMHO the clock setup & slack should be
> > handled equally. So I am asking the sched folks for a policy and I am
> > leaning towards looking at task-policy in this case instead of prio
> > because you shouldn't do anything that can delay.
> 
> Can't we do that based on is_soft/is_hard flag in hrtimer struct when we apply
> the slack in hrtimer_set_expires_range_ns() instead?

We need to decide on a policy first.
You don't want to add overhead on each invocation plus some in-kernel
ask for delta. ->is_soft is not a good criteria.

Sebastian