linux-kernel - Re: [PATCH] sched: Tweak default dynamic preempt mode selection

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Date:   Mon, 08 Nov 2021 13:27:06 +0100
From:   Mike Galbraith <efault@....de>
To:     Valentin Schneider <valentin.schneider@....com>,
        linux-kernel@...r.kernel.org
Cc:     Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...nel.org>,
        Frederic Weisbecker <frederic@...nel.org>
Subject: Re: [PATCH] sched: Tweak default dynamic preempt mode selection

On Mon, 2021-11-08 at 11:17 +0000, Valentin Schneider wrote:
> On 06/11/21 05:40, Mike Galbraith wrote:
> >
> > Starting with a 5.15 config, to select RT you currently must first
> > select a model you don't want, then reject PREEMPT_DYNAMIC and you'll
> > be offered the full menu of models immediately. With your patch added,
> > that became worse.  After rejecting PREEMPT_DYNAMIC, I had to go
> > through new 5.15+ options before finally being offered the full menu.
> >
>
> Do you mean at the syncconfig step?

Um, not sure what that is, but it sounds about right.

> I've only really played with upstream
> arm64 / x86 defconfigs and didn't have to fight with any prompts, though
> yes for x86 the default-y PREEMPT_DYNAMIC makes it a bit annoying to select
> PREEMPT_RT.

As long as RT depends on EXPERT it'll be a bit annoying regardless.  I
just thought it worth mention that what you want now and what RT will
presumably want upon merge completion appear to be mutually exclusive.

	-Mike