Re: NTP dumps Linux, film at 11. [Fwd/FYI]

Theodore Y. Ts'o (
Tue, 1 Dec 1998 12:40:54 -0500

Date: Mon, 30 Nov 1998 17:48:18 -0500
From: "Brandon S. Allbery KF8NH" <>

What's involved? We use NTP quite a lot, especially for the Linux
boxes (RH5 systems tend to drift a *lot* for some strange

Well, one thing which I recently noticed is that if you're using a
BusToaster SCSI PCMCIA card (great name, isn't it? :-) It's basically
Adaptec 152x controller), and you run mke2fs -c on a JAZ drive, your
clock will slow down an amazing amount --- over five minutes over the
course of that single command (which was enough to make Kerberos
complain about clock skew problems).

So there are at least a few device drivers which are apparently holding
interrupts off long enough so that we lose a clock interrupt. Not good,
and one of the reasons why any attempts to tweak the Linux scheduler to
make it a "real-time system" simply elicits a smile from me..... oh, if
only it were so easy! :-)

- Ted

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