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xen-devel
Re: [Xen-devel] timekeepeing in XEN - request fo comments
On Mon, Nov 09, 2009 at 08:50:52AM -0800, Dan Magenheimer wrote:
> What kernels are running in your domUs? Are they
> also (all) 2.6.31.5? If your domU's are older kernels
> (e.g. SLES10 or older, RHEL5 or older) there are
> many issues that cannot be entirely solved by
> Xen or dom0.
>
Could you tell more about these timekeeping problems with
SLES10/RHEL5 PV kernels?
-- Pasi
> > -----Original Message-----
> > From: Bartosz Lis [mailto:bartoszl@xxxxxxxxxxxxx]
> > Sent: Monday, November 09, 2009 5:21 AM
> > To: xen-devel@xxxxxxxxxxxxxxxxxxx
> > Subject: [Xen-devel] timekeepeing in XEN - request fo comments
> >
> >
> > Dear developers,
> >
> > I have some issues with time synchronization among dom0 and
> > domUs. In my case
> > helped reconfiguring kernel with HZ=1000 for dom0 and HZ=100
> > for domUs and
> > running ntpd also on domUs. I think, running ntpd on domU is
> > not a good idea,
> > but it works acceptably good as a workaround for my
> > configuration: XEN 3.4.1 +
> > kernel 3.6.31.5 with pv_ops (taken from git last week). When
> > I don't run ntpd
> > on domU clock slowly drifts. I have choosen xen clocksource
> > in both dom0 and
> > domU.
> >
> > I'm not the only one to have time synchronization issues.
> > Please write some
> > document specifying how time synchronization between dom0 and
> > domU should be
> > achieved. I have a number of special questions, but probably
> > there are more
> > questions that should be aswered:
> >
> > 1. What is the mechanics behind the clocksource named xen?
> > How does it depend
> > on phisical time sources available on different platforms?
> >
> > 2. How gets domU's clock initialized when domU boots? (I
> > observe that just
> > after domU has started its clock differs from dom0. The
> > difference is about
> > 10s.)
> >
> > 3. What are the consequences of not selecting xen clocksource
> > (by selecting
> > one of hpet, acpi_pm, etc.) for dom0 and for domU?
> >
> > 4. What are the best practices to achieve clock synchronization?
> >
> > 5. What has changed recently in timekeeping? What is going to
> > change? Are
> > there any improvements/bugfixes added to redhat or suse
> > kernels? Are these
> > bugfixes planned to be added upstream?
> >
> > Thank you in advance,
> >
> > --
> > Bartosz Lis @ Inst. of Information Technology, Technical
> > Univ. of Lodz, Poland
> > bartoszl @ ics.p.lodz.pl
> >
> > _______________________________________________
> > Xen-devel mailing list
> > Xen-devel@xxxxxxxxxxxxxxxxxxx
> > http://lists.xensource.com/xen-devel
> >
> >
>
> _______________________________________________
> Xen-devel mailing list
> Xen-devel@xxxxxxxxxxxxxxxxxxx
> http://lists.xensource.com/xen-devel
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