linux-kernel - Re: [PATCH v4] time/tick-sched: idle load balancing when nohz

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Date: Thu, 16 May 2024 17:12:33 +0100
From: Yun Levi <ppbuk5246@...il.com>
To: Frederic Weisbecker <frederic@...nel.org>
Cc: Peter Zijlstra <peterz@...radead.org>, Joel Fernandes <joel@...lfernandes.org>, 
	Vineeth Pillai <vineeth@...byteword.org>, Vincent Guittot <vincent.guittot@...aro.org>, 
	Dietmar Eggemann <dietmar.eggemann@....com>, anna-maria@...utronix.de, mingo@...nel.org, 
	tglx@...utronix.de, Markus.Elfring@....de, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v4] time/tick-sched: idle load balancing when nohz_full
 cpu becomes idle.

> > Yes, but stronger, as long as the CPU is part of a load-balance domain,
> > it must not disable the tick while running anything.
> >
> > that is, NOHZ_FULL must not become active unless it's running on a
> > single CPU partition.
>
> I like the idea but I'm afraid to introduce regressions while doing so,
> with people currently using nohz_full without proper partionning...

But I wonder when nohz_full cpu enters *idle".

If the cpuidle governor selects an idle state which wants "stop_tick",
If nohz_full cpu is still in sched domain, should it disable tick or not?