linux-kernel - Re: [RFC PATCH 2/2] tracing: add sched_set

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Message-ID: <d6a0e02e-99ea-4f54-d0aa-78e1db8a1c50@redhat.com>
Date:	Tue, 7 Jun 2016 21:18:41 -0300
From:	Daniel Bristot de Oliveira <daolivei@...hat.com>
To:	Peter Zijlstra <peterz@...radead.org>,
	Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
Cc:	Julien Desfossez <jdesfossez@...icios.com>,
	Ingo Molnar <mingo@...nel.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	rostedt <rostedt@...dmis.org>, linux-kernel@...r.kernel.org
Subject: Re: [RFC PATCH 2/2] tracing: add sched_set_prio tracepoint

On 06/06/2016 06:03 PM, Peter Zijlstra wrote:
>>>> > >> +/*
>>>> > >> + * Tracepoint for priority changes of a task.
>>>> > >> + */
>>>> > >> +DEFINE_EVENT(sched_prio_template, sched_set_prio,
>>>> > >> +		TP_PROTO(struct task_struct *tsk, int newprio),
>>>> > >> +		TP_ARGS(tsk, newprio));
>>>> > >> +
> Nak on anything that cannot fundamentally deal with SCHED_DEADLINE.

My 2 cents: I liked the idea... But, I agree with peterz. This cannot
fundamentally deal with deadline scheduler.

In the deadline scheduler, the priority is set at every new sporadic
activation of the task (it is a fixed job priority scheduler - not a
fixed priority scheduler). The priority is the deadline of the new job.
The deadline is an u64, that does not fit in the int prio - so it cannot
be reused.

-- Daniel