linux-kernel - Re: [PATCH] smpboot: reuse timer calibration

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Date:   Tue, 5 Nov 2019 11:05:45 +0100 (CET)
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Peter Zijlstra <peterz@...radead.org>
cc:     Paul Menzel <pmenzel@...gen.mpg.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        "H. Peter Anvin" <hpa@...or.com>,
        Arjan van de Ven <arjan@...ux.intel.com>, x86@...nel.org,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] smpboot: reuse timer calibration

On Tue, 29 Oct 2019, Peter Zijlstra wrote:
> On Tue, Oct 29, 2019 at 03:19:57PM +0100, Paul Menzel wrote:
> > From: Arjan van de Ven <arjan@...ux.intel.com>
> > Date: Wed, 11 Feb 2015 17:28:14 -0600
> > 
> > NO point recalibrating for known-constant tsc ...
> > saves 200ms+ of boot time.
> > 
> > Signed-off-by: Paul Menzel <pmenzel@...gen.mpg.de>
> > ---
> > 
> > Arjan, can your Signed-off-by line be added? On what device, did you test
> > this?
> 
> This patch makes no sense what so ever given the current function, also
> it hard codes 0 as being the BSP.
> 
> All of this for platforms (!constant_tsc) that barely exist anymore.

And it's only an issue on multi-socket systems with !constant_tsc, which
are even more rare.

Thanks,

	tglx