linux-kernel - Re: [RFC][PATCH] Adjust SHIFT_PLL to improve NTP convergence.

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Message-ID: <20090507060741.26571.qmail@science.horizon.com>
Date:	7 May 2009 02:07:41 -0400
From:	"George Spelvin" <linux@...izon.com>
To:	johnstul@...ibm.com, linux@...izon.com
Cc:	linux-kernel@...r.kernel.org, tglx@...utronix.de,
	ulrich.windl@...uni-regensburg.de, williams@...hat.com,
	zippel@...ux-m68k.org
Subject: Re: [RFC][PATCH] Adjust SHIFT_PLL to improve NTP convergence.

> Yea. The TSC calibration issue has been around for awhile. Although the
> code has been tweaked recently, I'm not seeing that much improved
> consistency from reboot to reboot.
> 
> Its a hard trade off for folks who need very quick boot time, vs folks
> that want very stable and accurate clocks across reboots.
> 
> I'll be looking into the calibration code to see how much is needed to
> bring the error rate down.

The fast estimate is very good.  Would it be possible to do a fine
calibration in parallel with the rest of the boot sequence?  Maybe until
the first adjtimex call?  Or is it essential that the numbers not
change?
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