Date: Fri, 16 Jul 2010 21:05:00 +0000 From: Bruce Cran <brucec@muon.cran.org.uk> To: Alexander Motin <mav@FreeBSD.org> Cc: Rob Farmer <rfarmer@predatorlabs.net>, current <current@freebsd.org> Subject: Re: Clock not moving in virtual machine Message-ID: <20100716210500.GA13257@muon.cran.org.uk> In-Reply-To: <4C40C55B.8040508@FreeBSD.org> References: <mailpost.1279239004.5520450.26216.mailing.freebsd.current@FreeBSD.cs.nctu.edu.tw> <4C3FFD3F.7060909@FreeBSD.org> <AANLkTilCKUtVEiViEN_EoCMGl7KvryVXEd-sWuxFjzsS@mail.gmail.com> <4C40C55B.8040508@FreeBSD.org>
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On Fri, Jul 16, 2010 at 11:47:23PM +0300, Alexander Motin wrote: > > It is probably hard to see pattern due to to very high clock frequency. > But TSC timecounter is unreliable even on real SMP systems. What it > counts on virtual SMP - even bigger question. As system seems never uses > timecounters with negative quality - you've left with > kern.timecounter.hardware=dummy - that's why time is not going. As last > resort you may try to set sysctl kern.timecounter.hardware=TSC in run time. I came across the same problem on rootbsd a few days ago, and set the TSC as the timecounter in /etc/sysctl.conf - I've since found it should be possible to also set kern.timecounter.smp_tsc=1 in /boot/loader.conf to let the TSC be chosen. The system's now been running for a day and I've not had any warnings about the clock going backward, and since the time has remained correct I guess Xen synchronises with the host? Should I still switch back to using the i8254? -- Bruce Cran
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