Re: [Xen-devel] timekeepeing in XEN - request fo comments

[Pasi Kärkkäinen <pasik@xxxxxx>]

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

_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxxxxxxxx
http://lists.xensource.com/xen-devel