[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] time drift on dom0
On Sun, Jan 16, 2005 at 09:17:58AM +0000, Keir Fraser wrote: > If you run NTPD in DOM0 then all other domains will be sync'ed to > DOM0's accurate timebase. This is how we run our own machines. Excellent! I didn't recall noticing any timing problems when I was playing with Xen (on a machine that has since moved on to other uses, so I don't have a working Xen testbed right now), but it was already running NTP in the system image that became dom0. Is this syncing what gives rise under some circumstances to the clock moving backwards that I've seen mentioned here? Never saw that, but I never got around to pushing that box hard. > The two main places we get drift from when not using NTP are > inaccuracy of the PIT oscillator (can easily be 100 or more ppm), and Yep. As I say, I've seen at least a couple different machines that run right around 200 ppm (one fast and one slow, as it happens) under non-Xen Linux. The frequencey correction is quite stable over the half year or so I've been logging the NTP stats. > Not much we can do about the former -- we could deal with the latter > by stretching/shrinking jiffies or by inserting leap jiffies. Seems like a waste of effort, given errors an order of magnitude larger than the nominal setting error. If you want accurate time, you need to run NTP anyway. :-) Or... was it adjtimex that I used to use back in the dark ages of dialup? Would that work to trim the dom0 clock error (it was more or less a manual correction for drift, as I recall)? -- Vs lbh pna ernq guvf, lbh'er va ivbyngvba bs gur Qvtvgny Zvyyraavhz Pbclevtug Npg. -- anon. ------------------------------------------------------- The SF.Net email is sponsored by: Beat the post-holiday blues Get a FREE limited edition SourceForge.net t-shirt from ThinkGeek. It's fun and FREE -- well, almost....http://www.thinkgeek.com/sfshirt _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxxxxxxxxxx https://lists.sourceforge.net/lists/listinfo/xen-devel
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