linux-kernel - Re: [PATCHv2] timekeeping: Update multiplier when NTP frequency is set directly

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Message-ID: <alpine.DEB.2.21.1806222327341.1589@nanos.tec.linutronix.de>
Date:   Fri, 22 Jun 2018 23:28:10 +0200 (CEST)
From:   Thomas Gleixner <tglx@...utronix.de>
To:     John Stultz <john.stultz@...aro.org>
cc:     Miroslav Lichvar <mlichvar@...hat.com>,
        lkml <linux-kernel@...r.kernel.org>,
        Richard Cochran <richardcochran@...il.com>,
        Prarit Bhargava <prarit@...hat.com>
Subject: Re: [PATCHv2] timekeeping: Update multiplier when NTP frequency is
 set directly

On Fri, 22 Jun 2018, John Stultz wrote:
> On Fri, Jun 22, 2018 at 2:09 PM, Thomas Gleixner <tglx@...utronix.de> wrote:
> > On Mon, 4 Jun 2018, Miroslav Lichvar wrote:
> >
> >> When the NTP frequency is set directly from userspace using the
> >> ADJ_FREQUENCY or ADJ_TICK timex mode, immediately update the
> >> timekeeper's multiplier instead of waiting for the next tick.
> >>
> >> This removes a hidden non-deterministic delay in setting of the
> >> frequency and allows an extremely tight control of the system clock
> >> with update rates close to or even exceeding the kernel HZ.
> >>
> >> The update is limited to archs using modern timekeeping
> >> (!ARCH_USES_GETTIMEOFFSET).
> >
> > John ?????
> 
> Yea. I've got this in my toqueue list.  I'm going to take another pass
> at testing and hopefully send it your way.

No hurry. I just wanted to make sure that it didn't fall through the
cracks.

Thanks,

	tglx