linux-kernel - Re: [PATCH v3] time/tick-sched: idle load balancing when nohz

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Message-ID: <CAM7-yPT7z6phHOUVOMxebRxiqw6un1N3hQK6O2AeRfmnJhK4kA@mail.gmail.com>
Date: Thu, 9 May 2024 10:22:10 +0100
From: Yun Levi <ppbuk5246@...il.com>
To: Markus Elfring <Markus.Elfring@....de>
Cc: kernel-janitors@...r.kernel.org, 
	Anna-Maria Behnsen <anna-maria@...utronix.de>, Frederic Weisbecker <frederic@...nel.org>, 
	Ingo Molnar <mingo@...nel.org>, Thomas Gleixner <tglx@...utronix.de>, 
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v3] time/tick-sched: idle load balancing when nohz_full
 cpu becomes idle.

Hi Markus.
.

> * Will any other data representation become more helpful for the circumstances
>   according to calls of a function like “tick_nohz_idle_stop_tick”?

Maybe not in this commit..?


> * How do you think about stress condition ordering concerns around
>   the system configuration “nohz_full”?

Well.. regardless of the stress condition, it wants to fix the
inconsistent behavior
happening when enter "idle state"

Let's think about two cases:
     1. nohz_full cpu stop tick in tick_nohz_irq_exiit() while it runs
only 1 cfs task.
     2. nohz_full cpu which doesn't stop the tick and switches to idle task.

Without this commit, case (1) wouldn't participate in idle balance
when it switches to idle task while its tick is already stopped.

case (2) although nohz_full cpu participates in idle balcancing
because former clock isn't stopped yet.


> * How will related changelogs evolve further?
>

Thanks for the suggestion. But I'll add some more background commit
message then.

Thanks again :)