On Fri, Jul 16, 2010 at 2:05 PM, Bruce Cran <bru...@muon.cran.org.uk> wrote: > 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 >
Setting kern.timecounter.smp_tsc=1 works for me. I put it in /boot/loader.conf so it would automatically work for single user mode too. I don't think the host automatically synchronizes the clock - their website recommends running ntp and I saw the clock drift a fair amount before I started doing that. Thanks for the tip. -- Rob Farmer _______________________________________________ freebsd-current@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-current To unsubscribe, send any mail to "freebsd-current-unsubscr...@freebsd.org"
