Re: [Xen-users] Clock problems on Squeeze/Xen4 (clock jumps 50 minutes ahead)

[Aleix Dorca Josa <adorca@xxxxxx>]

Stephan,

Just to clarify things the 'echo' command, where have you executed it, on the 
Dom0 or on the DomU, or on both?

On Ubuntu 12.04.1 running Xen 4.2.1 the setting are the same. It seems to be 
pretty straightforward. I'm going to try it right away.

Thanks a lot,

Aleix.

El 28/08/2012, a les 12:07, Stephan Seitz <s.seitz@xxxxxxxxxxx> va escriure:

> Hi,
> 
> as Ian already said, clocks are handled by the particular kernel(s).
> 
> On a recent CentOS 6, I'm using 
> 
> echo "tsc" > /sys/devices/system/clocksource/clocksource0/current_clocksource
> 
> That VM is currently running on top of a Xen 4.1.3.
> Oh, and it's running ntpd without problems.
> 
> I've just compared against the settings of an Ubuntu 12.04 on top of a Xen 
> 4.0.2
> and noticed, it's exactly the same.
> 
> I think the independent_wallclock key left the procfs a while ago. I'm not 
> quite
> sure, but I assume the result of having an independent clock can be achieved
> by only setting current_clocksource .
> 
> I don't have a Debian Squeeze VM at hand, so I can't tell which procfs / 
> sysfs keys
> are available.
> 
> Cheers,
> 
> Stephan
> 
> 
> 
> 
> 
> 
> 
> Am Dienstag, den 28.08.2012, 11:48 +0200 schrieb Aleix Dorca Josa:
>> Hi Stephan,
>> 
>> maybe I misunderstood but I was kind of sure that the 'jiffies' thing could 
>> not be used with Xen4.
>> 
>> I've looked at my domU and the jiffies clocksource is not available, only 
>> xen (the current one) and tsc.
>> Also on a Squeeze DomU there's no independent_wallclock on proc fs. Maybe it 
>> has another name?
>> 
>> I've used the timer_mode on some HVM domU's but I don't really remember 
>> why... I think it has nothing to do.
>> 
>> Thanks,
>> 
>> Aleix.
>> 
>> El 28/08/2012, a les 10:56, Ian Campbell <
>> Ian.Campbell@xxxxxxxxxx
>> > va escriure:
>> 
>> > On Mon, 2012-08-27 at 09:38 +0100, Aleix Dorca Josa wrote:
>> >> Hi Stephan,
>> >> 
>> >> thanks for your suggestion but unfortunately what you propose only works 
>> >> in Xen 3. I am using Xen 4.
>> > 
>> > What makes you say that? independent wallclock is a feature of the guest
>> > kernel not the hypervisor.
>> > 
>> > Older kernels might have /proc/sys/xen/independent_wallclock instead, or
>> > I think you can specify it on the guest kernel command line (you'll have
>> > to google the syntax, I don't know it offhand).
>> > 
>> > Ian.
>> > 
>> >> 
>> >> cheers,
>> >> 
>> >> Aleix.
>> >> 
>> >> El 27/08/2012, a les 10:30, Stephan Seitz <
>> s.seitz@xxxxxxxxxxx
>> > va escriure:
>> >> 
>> >>> 
>> >>> 
>> >>> Am Montag, den 27.08.2012, 08:29 +0200 schrieb Aleix Dorca Josa:
>> >>> 
>> >>>> I see that the clocksource=pit on the grub command line does not seem 
>> >>>> to fix the problem. Any other hints? Change to Ubuntu server? Build my 
>> >>>> own xen binary? Use Debian's backports to change the kernel version?
>> >>>> 
>> >>>> This is kind of a big problem for me since the error kills ntpd on 
>> >>>> DomU's and then Dovecot's processes stop themselves when time is 
>> >>>> corrected. Scripts to workaround this are fine but I would rather much 
>> >>>> prefer for the clock not to jump ahead.
>> >>>> 
>> >>> 
>> >>> Hi,
>> >>> 
>> >>> as a quick fix, you could handle your domU's independent from xen:
>> >>> 
>> >>> echo "jiffies" > 
>> >>> /sys/devices/system/clocksource/clocksource0/current_clocksource
>> >>> echo "1" > /proc/sys/xen/independent_wallclock
>> >>> 
>> >>> take a look at 
>> >>> /sys/devices/system/clocksource/clocksource0/available_clocksource to 
>> >>> see which clock sources are possible.
>> >>> 
>> >>> cheers,
>> >>> 
>> >>> Stephan
>> >> 
>> >> 
>> >> _______________________________________________
>> >> Xen-users mailing list
>> >> 
>> Xen-users@xxxxxxxxxxxxx
>> 
>> >> 
>> http://lists.xen.org/xen-users
>> 
>> > 
>> > 
>> 
>> 


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