linux-kernel - Re: [PATCH v2] IPI performance benchmark

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Message-ID: <CAOFm3uGjeT3waQaC+Ak=gmNkLFsFO6HshyEwsYA5QX2RjK0XNw@mail.gmail.com>
Date:   Tue, 19 Dec 2017 10:26:02 +0100
From:   Philippe Ombredanne <pombredanne@...b.com>
To:     Yury Norov <ynorov@...iumnetworks.com>
Cc:     LKML <linux-kernel@...r.kernel.org>, kvm@...r.kernel.org,
        "moderated list:ARM/FREESCALE IMX / MXC ARM ARCHITECTURE" 
        <linux-arm-kernel@...ts.infradead.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Ashish Kalra <Ashish.Kalra@...ium.com>,
        Christoffer Dall <christoffer.dall@...aro.org>,
        Geert Uytterhoeven <geert@...ux-m68k.org>,
        Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>,
        Linu Cherian <Linu.Cherian@...ium.com>,
        Shih-Wei Li <shihwei@...columbia.edu>,
        Sunil Goutham <Sunil.Goutham@...ium.com>,
        Aleksey Makarov <aleksey.makarov@...ium.com>
Subject: Re: [PATCH v2] IPI performance benchmark

Dear Yury,

On Tue, Dec 19, 2017 at 9:50 AM, Yury Norov <ynorov@...iumnetworks.com> wrote:
> This benchmark sends many IPIs in different modes and measures
> time for IPI delivery (first column), and total time, ie including
> time to acknowledge the receive by sender (second column).

<snip>

> --- /dev/null
> +++ b/kernel/ipi_benchmark.c
> @@ -0,0 +1,153 @@
> +/*
> + * Performance test for IPI on SMP machines.
> + *
> + * Copyright (c) 2017 Cavium Networks.
> + *
> + * This program is free software; you can redistribute it and/or
> + * modify it under the terms of version 2 of the GNU General Public
> + * License as published by the Free Software Foundation.
> + *
> + * This program is distributed in the hope that it will be useful, but
> + * WITHOUT ANY WARRANTY; without even the implied warranty of
> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
> + * General Public License for more details.
> + */

Would you mind using the new SPDX tags documented in Thomas patch set
[1] rather than this fine but longer legalese?  Each time long
legalese is added as a comment to a kernel file, there is a whole star
system that dies somewhere in the universe, which is not a good thing.

SPDX tags eschew this problem by using a simple one line comment and
this has been proven to be mostly harmless. And if you could spread
the word to others in your team this would be very nice. I recently
nudged Aleksey who nicely updated his patches a short while ago.

> +MODULE_LICENSE("GPL");

There is a problem here: your MODULE_LICENSE tag means GPL-2.0 or
later versions as documented in module.h. This is not consistent with
your top level license notice. You should make this consistent IMHO
.... and use SPDX tags for the top level notice of course!

Thank you!

[1] https://lkml.org/lkml/2017/12/4/934

CC: Aleksey Makarov <aleksey.makarov@...ium.com>
-- 
Cordially
Philippe Ombredanne