linux-kernel - Re: [PATCH v3 12/17] sched: Adapt sched tracepoints for RV task model

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Message-ID: <fe38ba0b9da0209bcc97c2f348f5a6b266991073.camel@redhat.com>
Date: Wed, 16 Jul 2025 16:07:16 +0200
From: Gabriele Monaco <gmonaco@...hat.com>
To: Peter Zijlstra <peterz@...radead.org>
Cc: linux-kernel@...r.kernel.org, Ingo Molnar <mingo@...hat.com>, Steven
 Rostedt <rostedt@...dmis.org>, Masami Hiramatsu <mhiramat@...nel.org>, 
	linux-trace-kernel@...r.kernel.org, Nam Cao <namcao@...utronix.de>, Tomas
 Glozar	 <tglozar@...hat.com>, Juri Lelli <jlelli@...hat.com>, Clark
 Williams	 <williams@...hat.com>, John Kacur <jkacur@...hat.com>
Subject: Re: [PATCH v3 12/17] sched: Adapt sched tracepoints for RV task
 model

On Wed, 2025-07-16 at 15:45 +0200, Peter Zijlstra wrote:
> 
> I'm not sure I understand the importance of IRQ state when describing
> task transitions.
> 
> You know both:
> 
>  - schedule() invocations for any one task are in-order;
>  - schedule() invocations for any one CPU are in-order.
> 

It's to describe latencies, which is the original purpose of the
scheduler model: if the event supposed to wake up an RT task occurs
with interrupts disabled while scheduling, we'd need to wait for that
run to complete.
Now to be fair, it doesn't really matter whether that call to
__schedule switches or not, but always having a switch event simplifies
things while modelling.
I can rearrange models like sts (added in this series) not to expect
that.

Thanks,
Gabriele