linux-kernel - Re: [PATCH/RFC] m68k: Add full preempt support

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Message-ID: <61d3b62380fb78b87003a09cc08827fb28de7942.camel@physik.fu-berlin.de>
Date:   Mon, 09 Oct 2023 13:45:37 +0200
From:   John Paul Adrian Glaubitz <glaubitz@...sik.fu-berlin.de>
To:     Geert Uytterhoeven <geert@...ux-m68k.org>,
        Greg Ungerer <gerg@...ux-m68k.org>,
        Ingo Molnar <mingo@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Juri Lelli <juri.lelli@...hat.com>,
        Vincent Guittot <vincent.guittot@...aro.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Matthew Wilcox <willy@...radead.org>
Cc:     linux-m68k@...ts.linux-m68k.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH/RFC] m68k: Add full preempt support

Hi Geert!

On Mon, 2023-10-09 at 13:29 +0200, Geert Uytterhoeven wrote:
> On Fri, Oct 6, 2023 at 4:49 PM Geert Uytterhoeven <geert@...ux-m68k.org> wrote:
> > Currently, a Preemptible Kernel is only supported on the Coldfire CPU
> > family.  Extend preempt support to the full Classic M68K CPU family
> > (68020+ with MMU, and 68000-derivatives without MMU).
> > 
> > Make sure preemption is disabled in loops involving cache and TLB
> > flushing.
> > 
> > Signed-off-by: Geert Uytterhoeven <geert@...ux-m68k.org>
> > ---
> > Tested on ARAnyM, using none/voluntary/full preemption.
> 
> bloat-o-meter summaries for atari_defconfig:
> 
> PREEMPT_NONE -> PREEMPT_VOLUNTARY:
> 
>     add/remove: 0/0 grow/shrink: 238/30 up/down: 2804/-748 (2056)
>     Total: Before=4478149, After=4480205, chg +0.05%
> 
> PREEMPT_VOLUNTARY -> PREEMPT:
> 
>     add/remove: 735/277 grow/shrink: 3050/347 up/down: 244359/-11440 (232919)
>     Total: Before=4480205, After=4713124, chg +5.20%
> 
> Ouch.

What exactly does the change document? More scheduling events?

Adrian

-- 
 .''`.  John Paul Adrian Glaubitz
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