Messages in this thread | | | Date | Sun, 23 Jul 2006 05:37:55 -0700 | From | Andrew Morton <> | Subject | Re: REGRESSION: the new i386 timer code fails to sync CPUs |
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On Sun, 23 Jul 2006 14:08:29 +0200 Matthias Urlichs <smurf@smurf.noris.de> wrote:
> Hi, > > Andrew Morton: > > - CPU0 and CPU1 share a TSC and CPU2 and CPU3 share another TSC. > > > That mmakes sense, since they're one dual-core Xeon each.
OK.
> > - Earlier kernels didn't use the TSC as a time source whereas this one > > does, hence the problems which you're observing. > > > Correct; see below. > > > I assume that booting with clock=pit or clock=pmtmr fixes it? > > > Testing... yes, both. > > > It would be useful to check your 2.6.17 boot logs, see if we can work out > > what 2.6.17 was using for a clock source. > > > That's easy: > > 2.6.17 -Using pmtmr for high-res timesource > 2.6.18git +Time: tsc clocksource has been installed. > > I missed those two lines, as in the boot logs they're not really > adjacent, so they got lost in the jumble of other differences.
OK, thanks. Marking the TSC as bad in this case is simple to do - let us let John work out the best way.
We must have lost a TSC sanity check somewhere along the way. I wonder what it was?
> Interestingly, CPU0/1 gets 6000 bogomips while CPU2/3 only reaches 5600 ..? > (That happens with both kernels.) I do wonder why, and whether this has any > bearing on the current problem.
I wouldn't expect it to matter, unless the TSCs are running at different speeds or something.
Also the sched-domain migration costs are grossly different between the two kernels. Maybe we changed the migration-cost-estimation code; I forget.
I'll see if we can get an expert opinion on the write_tsc() failure. - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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