linux-kernel - Re: Dhrystone -- userland version

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Message-ID: <CAMuHMdWQMoEBNQa2VKc3Ye1E6S8KjMh4w=T3Jqxr-yJBJ2U7iA@mail.gmail.com>
Date:   Mon, 9 Jan 2023 20:59:32 +0100
From:   Geert Uytterhoeven <geert@...ux-m68k.org>
To:     Pavel Machek <pavel@....cz>
Cc:     Willy Tarreau <w@....eu>, "Theodore Ts'o" <tytso@....edu>,
        kernel list <linux-kernel@...r.kernel.org>,
        Andrew Morton <akpm@...l.org>
Subject: Re: Dhrystone -- userland version

Hi Pavel,

On Mon, Jan 9, 2023 at 8:51 PM Pavel Machek <pavel@....cz> wrote:
> > >   count=1666675 us50=20178 us250=99913 diff=79735 cpu_MHz=4180.536 tsc50=42614718 tsc250=211016124 diff=101 rdtsc_MHz=2112.014
> > >
> > > It's also what's used by sbc-bench to verify that CPU vendors are not
> > > cheating in the embedded world. It's very simple, and not arch-dependent
> > > nor compiler-dependent (at least as long as you don't build at -O0 :-)).
> >
> > Seeing the rdtsc stuff, I was a bit skeptical, but it seems to work
> > fine on arm32 and rv64.
> >
> > Unfortunately you forgot to add a LICENSE file ;-)
> >
> > Alternatively, I can use the C version of BogoMIPS.  Which has its
> > own merits and reputation.
>
> I'd expect BogoMIPS to be _much_ worse than Dhrystone. If all the
> cores are same, it should be good enough, but...

Both give different results when run on little vs. big cores.
That's why my in-kernel version prints the CPU number, and supports
running multiple benchmarks in parallel.

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