linux-kernel - Re: [PATCH] sched/idle: Prevent stopping the tick when there is no cpuidle driver

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Message-ID: <87a5pag6q7.fsf@somnus>
Date: Fri, 12 Jan 2024 11:56:48 +0100
From: Anna-Maria Behnsen <anna-maria@...utronix.de>
To: Pierre Gondois <pierre.gondois@....com>, linux-kernel@...r.kernel.org
Cc: Ingo Molnar <mingo@...hat.com>, Peter Zijlstra <peterz@...radead.org>,
 Juri Lelli <juri.lelli@...hat.com>, Vincent Guittot
 <vincent.guittot@...aro.org>, Dietmar Eggemann <dietmar.eggemann@....com>,
 Steven Rostedt <rostedt@...dmis.org>, Ben Segall <bsegall@...gle.com>, Mel
 Gorman <mgorman@...e.de>, Daniel Bristot de Oliveira <bristot@...hat.com>,
 Valentin Schneider <vschneid@...hat.com>, Thomas Gleixner
 <tglx@...utronix.de>
Subject: Re: [PATCH] sched/idle: Prevent stopping the tick when there is no
 cpuidle driver

Pierre Gondois <pierre.gondois@....com> writes:

> Hello Anna-Maria,
>
> On 1/9/24 17:24, Anna-Maria Behnsen wrote:
>> 
>> When there is no cpuidle driver, there is no instance which could bring
>> the CPU into a deeper C state. But at the moment the code does
>> unconditionally try to stop the tick. So the aim of the patch is to
>> remove this unconditional stop of the tick.
>
> I agree that the absence of cpuidle driver prevents from reaching deep
> idle states. FWIU, there is however still benefits in stopping the tick
> on such platform.

What's the benefit?

Thanks,

        Anna-Maria