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

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Message-ID: <CAMuHMdVT7QEfagWcLx9z7YGtFiKRW5-J3F6gyxKYEzFBb=2_Gg@mail.gmail.com>
Date:   Mon, 9 Oct 2023 13:29:39 +0200
From:   Geert Uytterhoeven <geert@...ux-m68k.org>
To:     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

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.

Gr{oetje,eeting}s,

                        Geert


--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds