linux-kernel - Re: [PATCH -next v1] x86/apic: Reduce print level of CPU limit announcement

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Date:   Wed, 27 Mar 2019 13:36:28 +0200
From:   Leon Romanovsky <leon@...nel.org>
To:     Borislav Petkov <bp@...en8.de>
Cc:     Joe Perches <joe@...ches.com>,
        "Rafael J . Wysocki" <rafael@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, x86 <x86@...nel.org>,
        "H. Peter Anvin" <hpa@...or.com>,
        linux-pm <linux-pm@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH -next v1] x86/apic: Reduce print level of CPU limit
 announcement

On Wed, Mar 27, 2019 at 12:14:52PM +0100, Borislav Petkov wrote:
> On Wed, Mar 27, 2019 at 12:50:24PM +0200, Leon Romanovsky wrote:
> > It is how we are internally running verification and development,
> > with KERN_DEBUG level, we need it to catch bugs.
>
> And what is the big deal with seeing those messages? Why are *exactly*
> those two such a big problem and the gazillion other debug messages are
> fine?

At the end, it is reduced to our usage, we are running QEMU inside
docker to test kernel changes with limitation on number of CPUs to use.
The systems are optimized to boot kernel as soon as possible in order
to run tests and on my machine (64 CPUs) reduce is visible: from ~2.6
sec to ~2.3 sec from execution to kernel boot.

>
> > This "some config option" is dynamic debug prints and most probably it
> > is enabled in your or any kernel developer in the world.
>
> I personally don't use it because it only gets in the way.
>
> --
> Regards/Gruss,
>     Boris.
>
> Good mailing practices for 400: avoid top-posting and trim the reply.

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