linux-kernel - Re: [PATCH 0/5] Fix FIFO-99 abuse

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Message-ID: <20190802124151.GG2332@hirez.programming.kicks-ass.net>
Date:   Fri, 2 Aug 2019 14:41:51 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Qais Yousef <qais.yousef@....com>
Cc:     mingo@...nel.org, linux-kernel@...r.kernel.org,
        Geert Uytterhoeven <geert@...ux-m68k.org>,
        Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [PATCH 0/5] Fix FIFO-99 abuse

On Fri, Aug 02, 2019 at 11:26:12AM +0100, Qais Yousef wrote:

> Yes a somewhat enforced default makes more sense to me. I assume you no longer
> want to put the kthreads that just need to be above OTHER in FIFO-1?

I'm not sure, maybe, there's not that many of them, but possibly we add
another interface for them.

> While at it, since we will cram all kthreads on the same priority, isn't
> a SCHED_RR a better choice now? I think the probability of a clash is pretty
> low, but when it happens, shouldn't we try to guarantee some fairness?

It's never been a problem, and aside from these few straggler threads,
everybody has effectively been there already for years, so if it were a
problem someone would've complained by now.

Also; like said before, the admin had better configure.

Also also, RR-SMP is actually broken (and nobody has cared enough to
bother fixing it).