Messages in this thread | | | Date | Thu, 26 Feb 2009 14:24:25 -0800 (PST) | From | Linus Torvalds <> | Subject | Re: Linux 2.6.29-rc6 |
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On Thu, 26 Feb 2009, Thomas Gleixner wrote: > > Is the delta anything NTP might get upset about: > > 2.6.26: time.c: Detected 2311.847 MHz processor. > 2.6.29: Detected 2310.029 MHz processor. > > If yes, then we need to fix NTP not the calibration code :)
Well, that _is_ about 500ppm difference, and we claim that we _should_ have reached 150ppm with the 15ms delay. We clearly don't seem to have done that. I'm not quite sure why - we _should_ be finding the edge of the PIT events to within roughly a microsecond (assuming that's about as long as an "inb" takes), and that should give us a pretty good fast calibration, but maybe I'm overlooking something.
Or - and this may be more likely - there are chipsets that aren't very good at reading the PIT in a tight loop. That may explain why it's a problem on Jesper's hardware, but we haven't gotten tons of reports of this from others.
I see that it's a SunFire X2200, which I think uses an nVidia HT southbridge. I assume it's an nForce4 thing. There shouldn't be anything odd there, and the PIT read shouldn't be taking any longer than on anything else, but who knows?
Linus
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