linux-kernel - Re: [GIT pull] timers fixes for 2.6.31

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Date:	Fri, 07 Aug 2009 13:28:55 -0700
From:	john stultz <johnstul@...ibm.com>
To:	Martin Schwidefsky <schwidefsky@...ibm.com>
Cc:	Ingo Molnar <mingo@...e.hu>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Andrew Morton <akpm@...ux-foundation.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [GIT pull] timers fixes for 2.6.31

On Fri, 2009-08-07 at 10:18 +0200, Martin Schwidefsky wrote:
> On Thu, 6 Aug 2009 15:36:36 -0700
> john stultz <johnstul@...ibm.com> wrote:
>  
> > Splitting this up has been on my list for awhile, but I've never
> > gotten to it. However, Martin Schwidefsky has been doing a great job
> > with his latest patches cleaning up some of uglier parts of the
> > timekeeping/clocksource interactions. There is still lots of  changes
> > I'd like to see, but they will take time as we still haven't gotten
> > all the arches over to GENERIC_TIME, so some cruft has to stick
> > around.   But Martin's patches are a great big step towards it and
> > hopefully his patches will be ready for .32.
> 
> The question what we do with the mult_orig on clocksource
> enable/disable is one of the remaining open issues with my patch set.
> With the NTP adjusted multiplicator in the struct timekeeper we don't
> have a convenient place to keep the NTP adjusted multiplier while a
> clocksource is disabled. My initial thought was: why do we store the
> old multiplier at all? Its not that the clocksource changes all the
> time and NTP will catch up again if it is changed. Just start from
> scratch with the initial multiplicator.

Indeed, we don't need to store the adjusted multiplier while a
clocksource is not in use. We just have to make sure every time it is
used, we start with the same original multiplier, so we have a constant
base from which the NTP freq adjustment can be made upon.

I think you're approach (keeping the clocksource mult untouched, and
keeping the adjusted mult in the timekeeper structure)is fine.

thanks
-john

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