linux-kernel - Re: [PATCH v3 1/2] x86/vdso: Move mult and shift into struct vgtod

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Date:   Mon, 24 Jun 2019 11:40:02 +0200 (CEST)
From:   Thomas Gleixner <tglx@...utronix.de>
To:     "Sverdlin, Alexander (Nokia - DE/Ulm)" <alexander.sverdlin@...ia.com>
cc:     "x86@...nel.org" <x86@...nel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        "H. Peter Anvin" <hpa@...or.com>,
        Jason Vas Dias <jason.vas.dias@...il.com>,
        Andy Lutomirski <luto@...nel.org>
Subject: Re: [PATCH v3 1/2] x86/vdso: Move mult and shift into struct
 vgtod_ts

Alexander,

On Mon, 24 Jun 2019, Sverdlin, Alexander (Nokia - DE/Ulm) wrote:
> On 23/06/2019 12:18, Thomas Gleixner wrote:
> > The alternative solution for this is what Vincenzo has in his unified VDSO
> > patch series:
> > 
> >   https://lkml.kernel.org/r/20190621095252.32307-1-vincenzo.frascino@arm.com
> > 
> > It leaves the data struct unmodified and has a separate array for the raw
> > clock. That does not have the side effects at all.
> > 
> > I'm in the process of merging that series and I actually adapted your
> > scheme to the new unified infrastructure where it has exactly the same
> > effects as with your original patches against the x86 version.
> 
> please let me know if I need to rework [2/2] based on some not-yet-published
> branch of yours.

I've pushed it out now to

     git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git timers/vdso

The generic VDSO library has the support for RAW already with that separate
array. Testing would be welcomed!

Feel free to experiment with moving mult/shift again. Maybe you find a way
to mitigate the effects and make it all magically faster. :)

Thanks,

	tglx