Messages in this thread | | | Date | Fri, 29 Oct 2010 10:30:13 +0200 | From | Markus Trippelsdorf <> | Subject | Re: [bisected] Clocksource tsc unstable git |
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On Fri, Oct 29, 2010 at 10:18:31AM +0200, Borislav Petkov wrote: > On Wed, Oct 27, 2010 at 08:26:08PM +0200, markus@trippelsdorf.de wrote: > > During my search for a reliable testcase I found out that kvm guests also > > showed random hangs (that didn't happen in v2.6.36) here. These hangs last a > > few seconds each, during which the mouse is not movable at all. > > > > So I ran git-bisect with this testcase and the result of the bisection is: > > > > 34f971f6f7988be4d014eec3e3526bee6d007ffa is the first bad commit > > commit 34f971f6f7988be4d014eec3e3526bee6d007ffa > > Author: Peter Zijlstra <a.p.zijlstra@chello.nl> > > Date: Wed Sep 22 13:53:15 2010 +0200 > > > > ... > > > > > Reverting the commit solves the kvm hang issue. (If this issue is > > related to my original tsc problem is of course open for debate, but I > > have a strong hunch it is.) > > Well, what do you know, the temporary "slowdown" triggered on my setup > too. After waiting a minute maybe, the machine recovered and guess what > appeared in dmesg: > > [44729.650859] Clocksource tsc unstable (delta = -8615263009 ns) > [44729.656229] Switching to clocksource hpet > > I've reverted the changeset above and will run without it to check > whether it makes any difference.
After further testing I've found out that the tsc- and the kvm-issue are unrelated. IOW I get these "slowdowns" even with 34f971f6f7988be4 reverted.
I guess John was right when he wrote: > From your dmesg, I'd guess the hpet is the watchdog clocksource, so I > be on the lookout for hpet related changes. > > Maybe does reverting 995bd3bb5c78f3ff71339803c0b8337ed36d64fb hide the > issue?
Because with 995bd3bb5c78f reverted I never had a single "slowdown" here. -- Markus
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