linux-kernel - Re: [PATCH 2/3] x86/vdso: Allow clock specific mult and shift values

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Date:   Mon, 15 Apr 2019 11:51:38 +0200 (CEST)
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Huw Davies <huw@...eweavers.com>
cc:     linux kernel <linux-kernel@...r.kernel.org>,
        Andy Lutomirski <luto@...nel.org>,
        Vincenzo Frascino <vincenzo.frascino@....com>
Subject: Re: [PATCH 2/3] x86/vdso: Allow clock specific mult and shift
 values

On Mon, 15 Apr 2019, Huw Davies wrote:

> On Sun, Apr 14, 2019 at 12:53:32PM +0200, Thomas Gleixner wrote:
> > So it stays in the same cache line, but as we move the VDSO to generic
> > code, the mask field needs to stay and this will make basetime[CLOCK_MONOTONIC] 
> > overlap into the next cache line.
> 
> Thanks for the great review; this is a good point.
> 
> > See https://lkml.kernel.org/r/alpine.DEB.2.21.1902231727060.1666@nanos.tec.linutronix.de
> > for an alternate solution to this problem, which avoids this and just gives
> > CLOCK_MONOTONIC_RAW a separate storage space alltogether.
> 
> I can certainly do this for the x86 vdso.  Would that be useful or
> should I wait for Vincenzo's work on the generic vdso first?

Depends. If Vincenzo comes along with his new version soon, then you might
get this for free :)

Vincenzo, what's the state of your work?

Thanks,

	tglx