[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] RE: [PATCH] record max stime skew (was RE: [PATCH] strictly increasing hvm guest time)
On 10/7/08 01:24, "Dan Magenheimer" <dan.magenheimer@xxxxxxxxxx> wrote: > 7) CONJECTURE: Result of natural skews between platform > timer and tsc, plus jitter. Unfixable. > > Possible, untested, not sure how. I ended up suspecting this on one of the test platforms I originally did the Xen-system-time implementation on. It was an old AMD white box iirc. On that system, TSC and platform time seemed to have a significant and inexplicable jitter at around 1Hz. The jitter was 100s of ppm, which was totally unexpected for what should be crystal-based oscillators. And the test code was simple enough that it was hard to suspect that either (I think I was just dumping the counters every second or two after reading them as close together as I could). -- Keir _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxxxxxxxx http://lists.xensource.com/xen-devel
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