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

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Message-ID: <20190415093042.GA21726@merlot.physics.ox.ac.uk>
Date:   Mon, 15 Apr 2019 10:30:43 +0100
From:   Huw Davies <huw@...eweavers.com>
To:     Thomas Gleixner <tglx@...utronix.de>
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 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?

Many thanks,
Huw.