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Jordi Espasa Clofent

2009-Nov-03 17:54 UTC

[Xen-users] Time diferrence between dom0 and domU

Hi all,

In dom0:

xen01ad:/# ls -l /etc/localtime
lrwxrwxrwx 1 root root 33 2009-07-02 10:51 /etc/localtime -> 
/usr/share/zoneinfo/Europe/Madrid
xen01ad:/# ntpdate hora.rediris.es
  3 Nov 18:49:46 ntpdate[9558]: adjust time server 130.206.3.166 offset 
0.163783 sec

In domU:

xen-ad0006:~# date
Tue Nov  3 18:55:29 CET 2009
xen-ad0006:~# ls -l /etc/localtime
lrwxrwxrwx 1 root root 33 Nov  3 13:24 /etc/localtime -> 
/usr/share/zoneinfo/Europe/Madrid
xen-ad0006:~# ntpdate hora.rediris.es
  3 Nov 18:55:44 ntpdate[19800]: step time server 130.206.3.166 offset 
-294.467004 sec

As you can see, the time difference between dom0 and domU is aprox 6 min.
¿why?

It''s supposed that domUs has the dom0''s time.

Info:

* I don''t use the independent_wallclock
* xen01ad:/# uname -a && xm info
Linux xen01ad 2.6.18-6-xen-amd64 #1 SMP Tue May 5 09:56:33 UTC 2009 
x86_64 GNU/Linux
host                   : xen01ad
release                : 2.6.18-6-xen-amd64
version                : #1 SMP Tue May 5 09:56:33 UTC 2009
machine                : x86_64
nr_cpus                : 8
nr_nodes               : 1
cores_per_socket       : 4
threads_per_core       : 1
cpu_mhz                : 2110
hw_caps                : 
178bf3ff:efd3fbff:00000000:00000110:00802001:00000000:000037ff
total_memory           : 16383
free_memory            : 4161
node_to_cpu            : node0:0-7
xen_major              : 3
xen_minor              : 2
xen_extra              : -1
xen_caps               : xen-3.0-x86_64 xen-3.0-x86_32p hvm-3.0-x86_32 
hvm-3.0-x86_32p hvm-3.0-x86_64
xen_scheduler          : credit
xen_pagesize           : 4096
platform_params        : virt_start=0xffff800000000000
xen_changeset          : unavailable
cc_compiler            : gcc version 4.3.1 (Debian 4.3.1-2)
cc_compile_by          : waldi
cc_compile_domain      : debian.org
cc_compile_date        : Sat Jun 28 09:32:18 UTC 2008
xend_config_format     : 4

-- 
I must not fear. Fear is the mind-killer. Fear is the little-death that 
brings total obliteration. I will face my fear. I will permit it to pass 
over me and through me. And when it has gone past I will turn the inner 
eye to see its path. Where the fear has gone there will be nothing. Only 
I will remain.

Bene Gesserit Litany Against Fear.

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

Jordi Espasa Clofent

2009-Nov-05 08:21 UTC

head link

[Xen-users] Time diferrence between dom0 and domU

Hi all,

In dom0:

xen01ad:/# ls -l /etc/localtime
lrwxrwxrwx 1 root root 33 2009-07-02 10:51 /etc/localtime ->
/usr/share/zoneinfo/Europe/Madrid
xen01ad:/# ntpdate hora.rediris.es
  3 Nov 18:49:46 ntpdate[9558]: adjust time server 130.206.3.166 offset
0.163783 sec

In domU:

xen-ad0006:~# date
Tue Nov  3 18:55:29 CET 2009
xen-ad0006:~# ls -l /etc/localtime
lrwxrwxrwx 1 root root 33 Nov  3 13:24 /etc/localtime ->
/usr/share/zoneinfo/Europe/Madrid
xen-ad0006:~# ntpdate hora.rediris.es
  3 Nov 18:55:44 ntpdate[19800]: step time server 130.206.3.166 offset
-294.467004 sec

As you can see, the time difference between dom0 and domU is aprox 6 min.
¿why?

It''s supposed that domUs has the dom0''s time.

Info:

* I don''t use the independent_wallclock
* xen01ad:/# uname -a && xm info
Linux xen01ad 2.6.18-6-xen-amd64 #1 SMP Tue May 5 09:56:33 UTC 2009
x86_64 GNU/Linux
host                   : xen01ad
release                : 2.6.18-6-xen-amd64
version                : #1 SMP Tue May 5 09:56:33 UTC 2009
machine                : x86_64
nr_cpus                : 8
nr_nodes               : 1
cores_per_socket       : 4
threads_per_core       : 1
cpu_mhz                : 2110
hw_caps                :
178bf3ff:efd3fbff:00000000:00000110:00802001:00000000:000037ff
total_memory           : 16383
free_memory            : 4161
node_to_cpu            : node0:0-7
xen_major              : 3
xen_minor              : 2
xen_extra              : -1
xen_caps               : xen-3.0-x86_64 xen-3.0-x86_32p hvm-3.0-x86_32
hvm-3.0-x86_32p hvm-3.0-x86_64
xen_scheduler          : credit
xen_pagesize           : 4096
platform_params        : virt_start=0xffff800000000000
xen_changeset          : unavailable
cc_compiler            : gcc version 4.3.1 (Debian 4.3.1-2)
cc_compile_by          : waldi
cc_compile_domain      : debian.org
cc_compile_date        : Sat Jun 28 09:32:18 UTC 2008
xend_config_format     : 4

-- 
I must not fear. Fear is the mind-killer. Fear is the little-death that
brings total obliteration. I will face my fear. I will permit it to pass
over me and through me. And when it has gone past I will turn the inner
eye to see its path. Where the fear has gone there will be nothing. Only
I will remain.

Bene Gesserit Litany Against Fear.


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

Bartosz Lis

2009-Nov-06 09:20 UTC

head link

Re: [Xen-users] Time diferrence between dom0 and domU

Dnia wtorek, 3 listopada 2009 o 18:54:04 Jordi Espasa Clofent
napisał(a):> Hi all,
> 
> In dom0:
> 
> xen01ad:/# ls -l /etc/localtime
> lrwxrwxrwx 1 root root 33 2009-07-02 10:51 /etc/localtime ->
> /usr/share/zoneinfo/Europe/Madrid
> xen01ad:/# ntpdate hora.rediris.es
>   3 Nov 18:49:46 ntpdate[9558]: adjust time server 130.206.3.166 offset
> 0.163783 sec
> 
> In domU:
> 
> xen-ad0006:~# date
> Tue Nov  3 18:55:29 CET 2009
> xen-ad0006:~# ls -l /etc/localtime
> lrwxrwxrwx 1 root root 33 Nov  3 13:24 /etc/localtime ->
> /usr/share/zoneinfo/Europe/Madrid
> xen-ad0006:~# ntpdate hora.rediris.es
>   3 Nov 18:55:44 ntpdate[19800]: step time server 130.206.3.166 offset
> -294.467004 sec
> 
> As you can see, the time difference between dom0 and domU is aprox 6 min.
> ¿why?
> 
> It''s supposed that domUs has the dom0''s time.
> 
> Info:
> 
> * I don''t use the independent_wallclock
> * xen01ad:/# uname -a && xm info
> Linux xen01ad 2.6.18-6-xen-amd64 #1 SMP Tue May 5 09:56:33 UTC 2009
> x86_64 GNU/Linux
> host                   : xen01ad
> release                : 2.6.18-6-xen-amd64
> version                : #1 SMP Tue May 5 09:56:33 UTC 2009
> machine                : x86_64
> nr_cpus                : 8
> nr_nodes               : 1
> cores_per_socket       : 4
> threads_per_core       : 1
> cpu_mhz                : 2110
> hw_caps                :
> 178bf3ff:efd3fbff:00000000:00000110:00802001:00000000:000037ff
> total_memory           : 16383
> free_memory            : 4161
> node_to_cpu            : node0:0-7
> xen_major              : 3
> xen_minor              : 2
> xen_extra              : -1
> xen_caps               : xen-3.0-x86_64 xen-3.0-x86_32p hvm-3.0-x86_32
> hvm-3.0-x86_32p hvm-3.0-x86_64
> xen_scheduler          : credit
> xen_pagesize           : 4096
> platform_params        : virt_start=0xffff800000000000
> xen_changeset          : unavailable
> cc_compiler            : gcc version 4.3.1 (Debian 4.3.1-2)
> cc_compile_by          : waldi
> cc_compile_domain      : debian.org
> cc_compile_date        : Sat Jun 28 09:32:18 UTC 2008
> xend_config_format     : 4
> 
Jordi,

I''m facing similar problems. My ocnfiguration: XEN 3.4.1 + kernel from 
http://git.kernel.org/?p=linux/kernel/git/jeremy/xen.git;a=shortlog;h=xen/master

I observe problems:

1. Just afer DomU starts it''s time differs from dom0 clocks: software
(date)
and hardware (hwclock --show --utc). In my case it''s ~10s.
It''s not caused by
wrong /etc/localtime. If it were, then round hours would be the difference. 

2. DomU''s clock drifts.

I''ve made 2 things as a workaround:

1. I''ve installed ntpd in domU, too. I read somewhere that it sould be
done as
a workaround, until the source of te poblem is found and fixed. With ntpd 
running DomU''s clock still drifted, but when the difference was
approaching 1s
ntpd reseted the clock. 

2. I''ve changed timer interrupt frequencies to 1000Hz in dom0 and to
100Hz in
domU. That was done by kernel recompilation, of course. Now, domU''s
clocks
differ from dom0 in range ~10ms when under small load or ~100ms under havy 
load. Furthemore, the differences are steady - I do not observe leaps as It 
was when domU and dom0 timer interrupt frequencies were equal.

It''s also handy to do:

3. On dom0 put into /etc/cron.hourly a script doing:
/sbin/hwclock --systohc --utc

I''m going to report my problems to xen-devel and ask them to write some
wiki
article on time keeping.

Kind regards,

-- 
Bartosz Lis @ Institute of Comp. Science, Technical University of Lodz, Poland
   bartoszl @ ics.p.lodz.pl

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

Jordi Espasa Clofent

2009-Nov-06 09:43 UTC

head link

Re: [Xen-users] Time diferrence between dom0 and domU

First of all, thanks for your response Bartosz. ;)
> I''m facing similar problems. My ocnfiguration: XEN 3.4.1 + kernel
from
>
http://git.kernel.org/?p=linux/kernel/git/jeremy/xen.git;a=shortlog;h=xen/master
I''ve suffered this trouble since 3.0.x version. What a pity!
> 1. Just afer DomU starts it''s time differs from dom0 clocks:
software (date)
> and hardware (hwclock --show --utc). In my case it''s ~10s.
It''s not caused by
> wrong /etc/localtime. If it were, then round hours would be the difference.
Mmmm... I think I don''t understand completely what you say. Could you 
elaborate more this argument please?
> 2. DomU''s clock drifts.
> 
> I''ve made 2 things as a workaround:
> 
> 1. I''ve installed ntpd in domU, too. I read somewhere that it
sould be done as
> a workaround, until the source of te poblem is found and fixed. With ntpd 
> running DomU''s clock still drifted, but when the difference was
approaching 1s
> ntpd reseted the clock. 
Yes. I''ve also tried to set up a ntpd in domU (activating the 
independent_wallclock entry in /proc)
but it seems not works at all.
> 2. I''ve changed timer interrupt frequencies to 1000Hz in dom0 and
to 100Hz in
> domU. That was done by kernel recompilation, of course. Now,
domU''s clocks
> differ from dom0 in range ~10ms when under small load or ~100ms under havy 
> load. Furthemore, the differences are steady - I do not observe leaps as It
> was when domU and dom0 timer interrupt frequencies were equal.
So... ¿Can I suppose that the time difference ocurrs because the domUs 
are under high load?
> It''s also handy to do:
> 
> 3. On dom0 put into /etc/cron.hourly a script doing:
> /sbin/hwclock --systohc --utc
¿What it means exactly?
> I''m going to report my problems to xen-devel and ask them to write
some wiki
> article on time keeping.
Yes, I thing is absolutely needed. As I''ve said before, I''ve
experienced
time sync problems between dom0 and domUs since 3.0.x version; and now 
you''re talking about 3.4.x version. It''s totally unacceptable.
Keeping
the time sync is an esencial feature.

-- 
I must not fear. Fear is the mind-killer. Fear is the little-death that 
brings total obliteration. I will face my fear. I will permit it to pass 
over me and through me. And when it has gone past I will turn the inner 
eye to see its path. Where the fear has gone there will be nothing. Only 
I will remain.

Bene Gesserit Litany Against Fear.

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

Fajar A. Nugraha

2009-Nov-06 09:52 UTC

head link

Re: [Xen-users] Time diferrence between dom0 and domU

On Fri, Nov 6, 2009 at 4:43 PM, Jordi Espasa Clofent
<jespasac@minibofh.org> wrote:> First of all, thanks for your response Bartosz. ;)
>
>> I''m facing similar problems. My ocnfiguration: XEN 3.4.1 +
kernel from
>>
http://git.kernel.org/?p=linux/kernel/git/jeremy/xen.git;a=shortlog;h=xen/master
>
> I''ve suffered this trouble since 3.0.x version. What a pity!
Workaround: if it''s PV domU, use RHEL/Centos5''s kernel-xen
(xen.org''s
2.6.18 kernel may also work). I use it with both Redhat''s version of
Xen and Xen 3.4.1, it doesn''t have the problem.

-- 
Fajar

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

Pasi Kärkkäinen

2009-Nov-06 11:29 UTC

head link

Re: [Xen-users] Time diferrence between dom0 and domU

On Fri, Nov 06, 2009 at 04:52:24PM +0700, Fajar A. Nugraha
wrote:> On Fri, Nov 6, 2009 at 4:43 PM, Jordi Espasa Clofent
> <jespasac@minibofh.org> wrote:
> > First of all, thanks for your response Bartosz. ;)
> >
> >> I''m facing similar problems. My ocnfiguration: XEN 3.4.1
+ kernel from
> >>
http://git.kernel.org/?p=linux/kernel/git/jeremy/xen.git;a=shortlog;h=xen/master
> >
> > I''ve suffered this trouble since 3.0.x version. What a pity!
> 
> Workaround: if it''s PV domU, use RHEL/Centos5''s
kernel-xen (xen.org''s
> 2.6.18 kernel may also work). I use it with both Redhat''s version
of
> Xen and Xen 3.4.1, it doesn''t have the problem.
> 
Does someone if this is a problem/bug in the dom0 kernel? 
Or is it a problem with the hypervisor, or domU kernel? 

Does changing _only_ dom0 kernel fix it?

-- Pasi


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

Pasi Kärkkäinen

2009-Nov-06 12:33 UTC

head link

Re: [Xen-users] Time diferrence between dom0 and domU

On Fri, Nov 06, 2009 at 01:29:58PM +0200, Pasi Kärkkäinen
wrote:> On Fri, Nov 06, 2009 at 04:52:24PM +0700, Fajar A. Nugraha wrote:
> > On Fri, Nov 6, 2009 at 4:43 PM, Jordi Espasa Clofent
> > <jespasac@minibofh.org> wrote:
> > > First of all, thanks for your response Bartosz. ;)
> > >
> > >> I''m facing similar problems. My ocnfiguration: XEN
3.4.1 + kernel from
> > >>
http://git.kernel.org/?p=linux/kernel/git/jeremy/xen.git;a=shortlog;h=xen/master
> > >
> > > I''ve suffered this trouble since 3.0.x version. What a
pity!
> > 
> > Workaround: if it''s PV domU, use RHEL/Centos5''s
kernel-xen (xen.org''s
> > 2.6.18 kernel may also work). I use it with both Redhat''s
version of
> > Xen and Xen 3.4.1, it doesn''t have the problem.
> > 
> 
> Does someone if this is a problem/bug in the dom0 kernel?                ^+know
> Or is it a problem with the hypervisor, or domU kernel? 
> 
> Does changing _only_ dom0 kernel fix it?
> 
> -- Pasi
> 

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

Jordi Espasa Clofent

2009-Nov-06 13:29 UTC

head link

Re: [Xen-users] Time diferrence between dom0 and domU

> Workaround: if it''s PV domU, use RHEL/Centos5''s
kernel-xen (xen.org''s
> 2.6.18 kernel may also work). I use it with both Redhat''s version
of
> Xen and Xen 3.4.1, it doesn''t have the problem.
Thanks for the advice Fajar, but my environment is:

xen05:~# uname -a && xm info
Linux xen05 2.6.18-6-xen-amd64 #1 SMP Thu Dec 25 22:21:42 UTC 2008 
x86_64 GNU/Linux
host                   : xen05
release                : 2.6.18-6-xen-amd64
version                : #1 SMP Thu Dec 25 22:21:42 UTC 2008
machine                : x86_64
nr_cpus                : 8
nr_nodes               : 1
cores_per_socket       : 4
threads_per_core       : 1
cpu_mhz                : 1909
hw_caps                : 
178bf3ff:efd3fbff:00000000:00000110:00802001:00000000:000007ff
total_memory           : 8191
free_memory            : 1919
node_to_cpu            : node0:0-7
xen_major              : 3
xen_minor              : 2
xen_extra              : -1
xen_caps               : xen-3.0-x86_64 xen-3.0-x86_32p hvm-3.0-x86_32 
hvm-3.0-x86_32p hvm-3.0-x86_64
xen_scheduler          : credit
xen_pagesize           : 4096
platform_params        : virt_start=0xffff800000000000
xen_changeset          : unavailable
cc_compiler            : gcc version 4.3.1 (Debian 4.3.1-2)
cc_compile_by          : waldi
cc_compile_domain      : debian.org
cc_compile_date        : Sat Jun 28 09:32:18 UTC 2008
xend_config_format     : 4

And it''s a production environment. I haven''t the option that
you comment. :(


-- 
I must not fear. Fear is the mind-killer. Fear is the little-death that 
brings total obliteration. I will face my fear. I will permit it to pass 
over me and through me. And when it has gone past I will turn the inner 
eye to see its path. Where the fear has gone there will be nothing. Only 
I will remain.

Bene Gesserit Litany Against Fear.

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

Bartosz Lis

2009-Nov-06 14:24 UTC

head link

Re: [Xen-users] Time diferrence between dom0 and domU

Dnia piątek, 6 listopada 2009 o 10:43:47 Jordi Espasa Clofent
napisał(a):> First of all, thanks for your response Bartosz. ;)
> 
> > I''m facing similar problems. My ocnfiguration: XEN 3.4.1 +
kernel from
> >
http://git.kernel.org/?p=linux/kernel/git/jeremy/xen.git;a=shortlog;h=xen
> >/master
> 
> I''ve suffered this trouble since 3.0.x version. What a pity!
> 
> > 1. Just afer DomU starts it''s time differs from dom0 clocks:
software
> > (date) and hardware (hwclock --show --utc). In my case it''s
~10s. It''s
> > not caused by wrong /etc/localtime. If it were, then round hours would
be
> > the difference.
> 
> Mmmm... I think I don''t understand completely what you say. Could
you
> elaborate more this argument please?
> Jordi,

Sorry for writing the above line in a hurry.

I observe, that my domU clock differs from dom0 clock from the very beginning. 
Thus I think it''s something wrong with xen tools that setup a new
domain or
the prblem is caused by hypervisor or kernel that miss some number of clock 
ticks during kernel boot. 

The difference is ~10s so it''s not caused by wrong /etc/localtime. If
one uses
/etc/localtime generated by some distribution (RedHat, Suse, Debian or PLD in 
my case) the difference should not be a fraction of an hour. 
> > 1. I''ve installed ntpd in domU, too. I read somewhere that it
sould be
> > done as a workaround, until the source of te poblem is found and
fixed.
> > With ntpd running DomU''s clock still drifted, but when the
difference was
> > approaching 1s ntpd reseted the clock.
> 
> Yes. I''ve also tried to set up a ntpd in domU (activating the
> independent_wallclock entry in /proc)
> but it seems not works at all.
In my combination of Xen(3.4.1)/kernel(2.6.31.5/jeremy) I have no such entry 
in the /proc tree or I don''t know how to make independent_wallclock
entry
apear somewhere there. But the workaround works without writing to this entry.
> > 2. I''ve changed timer interrupt frequencies to 1000Hz in dom0
and to
> > 100Hz in domU. That was done by kernel recompilation, of course. Now,
> > domU''s clocks differ from dom0 in range ~10ms when under
small load or
> > ~100ms under havy load. Furthemore, the differences are steady - I do
not
> > observe leaps as It was when domU and dom0 timer interrupt frequencies
> > were equal.
> 
> So... ¿Can I suppose that the time difference ocurrs because the domUs
> are under high load?
Well, it seems that hypervisor''s mechanisms of sharing common clock
between
domains don''t work. What works, is ntpd based synchronization
independent of
xen. Ntpd daemon works in userspace and it behaves better when the system is 
not fully loaded. The load I was talking about is my favorite load test: linux 
kernel compilation, do it again and again using at least 20 concurent jobs.
> 
> > It''s also handy to do:
> >
> > 3. On dom0 put into /etc/cron.hourly a script doing:
> > /sbin/hwclock --systohc --utc
> 
> ¿What it means exactly?
Once every hour my serwer rewrites time from its clock kept by linux to 
hardware clock. Linux clock is, of course, continuously synchronized by ntpd. 
In case of a sudden crash, server reboots with hardware clock very close to 
world clocks.

Kind regards,

-- 
Bartosz Lis @ Institute of Comp. Science, Technical University of Lodz, Poland
   bartoszl @ ics.p.lodz.pl

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

Bartosz Lis

2009-Nov-06 14:35 UTC

head link

Re: [Xen-users] Time diferrence between dom0 and domU

Dnia piątek, 6 listopada 2009 o 15:24:29 Bartosz Lis
napisał(a):> Dnia piątek, 6 listopada 2009 o 10:43:47 Jordi Espasa Clofent napisał(a):
> > First of all, thanks for your response Bartosz. ;)
> >
> > > I''m facing similar problems. My ocnfiguration: XEN 3.4.1
+ kernel from
> > >
http://git.kernel.org/?p=linux/kernel/git/jeremy/xen.git;a=shortlog;h=x
> > >en /master
> >
> > I''ve suffered this trouble since 3.0.x version. What a pity!
> >
> > > 1. Just afer DomU starts it''s time differs from dom0
clocks: software
> > > (date) and hardware (hwclock --show --utc). In my case
it''s ~10s. It''s
> > > not caused by wrong /etc/localtime. If it were, then round hours
would
> > > be the difference.
> >
> > Mmmm... I think I don''t understand completely what you say.
Could you
> > elaborate more this argument please?
> 
> Jordi,
> 
> Sorry for writing the above line in a hurry.
> 
> I observe, that my domU clock differs from dom0 clock from the very
>  beginning. 
... still writing in a hurry ... I mean: from the very beginning of domU work 
- probably domU boots with distorted time.
>  Thus I think it''s something wrong with xen tools that setup a
>  new domain or the prblem is caused by hypervisor or kernel that miss some
>  number of clock ticks during kernel boot.

-- 
Bartosz Lis @ Institute of Comp. Science, Technical University of Lodz, Poland
   bartoszl @ ics.p.lodz.pl

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

Jordi Espasa Clofent

2009-Nov-09 12:32 UTC

head link

Re: [Xen-users] Time diferrence between dom0 and domU

> Jordi,
> 
> Sorry for writing the above line in a hurry.
No problem.
> I observe, that my domU clock differs from dom0 clock from the very
beginning.
> Thus I think it''s something wrong with xen tools that setup a new
domain or
> the prblem is caused by hypervisor or kernel that miss some number of clock
> ticks during kernel boot. 
IMHO this is important. Is there any related bug at "official level"?
> In my combination of Xen(3.4.1)/kernel(2.6.31.5/jeremy) I have no such
entry
> in the /proc tree or I don''t know how to make
independent_wallclock entry
> apear somewhere there. But the workaround works without writing to this
entry.
Ok.
> Well, it seems that hypervisor''s mechanisms of sharing common
clock between
> domains don''t work. What works, is ntpd based synchronization
independent of
> xen. Ntpd daemon works in userspace and it behaves better when the system
is
> not fully loaded. The load I was talking about is my favorite load test:
linux
> kernel compilation, do it again and again using at least 20 concurent jobs.
So, I understand the problem could be if you rely in ntpd (userspace) to 
keep up the time sync and the domU is under high load (kernel space). No?

Anyway, the solution is clear: the hypervisor must to do it correctly.

-- 
I must not fear. Fear is the mind-killer. Fear is the little-death that 
brings total obliteration. I will face my fear. I will permit it to pass 
over me and through me. And when it has gone past I will turn the inner 
eye to see its path. Where the fear has gone there will be nothing. Only 
I will remain.

Bene Gesserit Litany Against Fear.

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Bartosz Lis

2009-Nov-10 15:08 UTC

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Re: [Xen-users] Time diferrence between dom0 and domU

Dnia poniedziałek, 9 listopada 2009 o 13:32:11 Jordi Espasa Clofent 
napisał(a):> > Jordi,
> >
> > Sorry for writing the above line in a hurry.
> 
> No problem.
> 
> > I observe, that my domU clock differs from dom0 clock from the very
> > beginning. Thus I think it''s something wrong with xen tools
that setup a
> > new domain or the prblem is caused by hypervisor or kernel that miss
some
> > number of clock ticks during kernel boot.
> 
> IMHO this is important. Is there any related bug at "official
level"?
> 
> > In my combination of Xen(3.4.1)/kernel(2.6.31.5/jeremy) I have no such
> > entry in the /proc tree or I don''t know how to make
independent_wallclock
> > entry apear somewhere there. But the workaround works without writing
to
> > this entry.
> 
> Ok.
> 
> > Well, it seems that hypervisor''s mechanisms of sharing common
clock
> > between domains don''t work. What works, is ntpd based
synchronization
> > independent of xen. Ntpd daemon works in userspace and it behaves
better
> > when the system is not fully loaded. The load I was talking about is
my
> > favorite load test: linux kernel compilation, do it again and again
using
> > at least 20 concurent jobs.
> 
> So, I understand the problem could be if you rely in ntpd (userspace) to
> keep up the time sync and the domU is under high load (kernel space). No?
> 
> Anyway, the solution is clear: the hypervisor must to do it correctly.
> 
Jordi,

I just got answer from Jeremy Fitzhardinge to my questions regarding 
timekeepeing sent to xen-devel. See: 
http://lists.xensource.com/archives/html/xen-devel/2009-11/msg00505.html .

The good news for me is that it''s not that bad as I thought with
2.6.31.5
kernels. Generally, xen makes dom0 and domU clocks go in lockstep with its 
wallclock, but at the moment you cannot update xen wallclock from dom0 (nor 
from domU). When this feature is implemented, the problem should disappear in 
2.6.31+ kernels. Util that moment I''ll have to run ntpd in all VMs. I
think
200ms time difference, which I have under heavy load, is not a big issue. Of 
course, that''s my point of view and your applications might be more
strict.

If you are interested in older kernels, please, join the discussion on xen-
devel: http://lists.xensource.com/archives/html/xen-
devel/2009-11/msg00469.html

-- 
Bartosz Lis @ Inst. of Information Technology, Technical Univ. of Lodz, Poland
   bartoszl @ ics.p.lodz.pl

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Matthieu Patou

2009-Nov-10 21:03 UTC

head link

Re: [Xen-users] Time diferrence between dom0 and domU

Hello Jordi,
I noticed the same problem and that''s pretty nasty on HVM host running 
windows as the system can''t login on domain by defaut due to too big 
time drift.

I worked around by adding ~ 6 minutes to the time of the domU at startup.

On 05/11/2009 11:21, Jordi Espasa Clofent wrote:> Hi all,
>
> In dom0:
>
> xen01ad:/# ls -l /etc/localtime
> lrwxrwxrwx 1 root root 33 2009-07-02 10:51 /etc/localtime ->
> /usr/share/zoneinfo/Europe/Madrid
> xen01ad:/# ntpdate hora.rediris.es
> 3 Nov 18:49:46 ntpdate[9558]: adjust time server 130.206.3.166 offset
> 0.163783 sec
>
> In domU:
>
> xen-ad0006:~# date
> Tue Nov 3 18:55:29 CET 2009
> xen-ad0006:~# ls -l /etc/localtime
> lrwxrwxrwx 1 root root 33 Nov 3 13:24 /etc/localtime ->
> /usr/share/zoneinfo/Europe/Madrid
> xen-ad0006:~# ntpdate hora.rediris.es
> 3 Nov 18:55:44 ntpdate[19800]: step time server 130.206.3.166 offset
> -294.467004 sec
>
> As you can see, the time difference between dom0 and domU is aprox 6 min.
> ¿why?
>
> It''s supposed that domUs has the dom0''s time.
>
> Info:
>
> * I don''t use the independent_wallclock
> * xen01ad:/# uname -a && xm info
> Linux xen01ad 2.6.18-6-xen-amd64 #1 SMP Tue May 5 09:56:33 UTC 2009
> x86_64 GNU/Linux
> host : xen01ad
> release : 2.6.18-6-xen-amd64
> version : #1 SMP Tue May 5 09:56:33 UTC 2009
> machine : x86_64
> nr_cpus : 8
> nr_nodes : 1
> cores_per_socket : 4
> threads_per_core : 1
> cpu_mhz : 2110
> hw_caps :
> 178bf3ff:efd3fbff:00000000:00000110:00802001:00000000:000037ff
> total_memory : 16383
> free_memory : 4161
> node_to_cpu : node0:0-7
> xen_major : 3
> xen_minor : 2
> xen_extra : -1
> xen_caps : xen-3.0-x86_64 xen-3.0-x86_32p hvm-3.0-x86_32
> hvm-3.0-x86_32p hvm-3.0-x86_64
> xen_scheduler : credit
> xen_pagesize : 4096
> platform_params : virt_start=0xffff800000000000
> xen_changeset : unavailable
> cc_compiler : gcc version 4.3.1 (Debian 4.3.1-2)
> cc_compile_by : waldi
> cc_compile_domain : debian.org
> cc_compile_date : Sat Jun 28 09:32:18 UTC 2008
> xend_config_format : 4
>

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Pasi Kärkkäinen

2009-Nov-11 09:32 UTC

head link

Re: [Xen-users] Time diferrence between dom0 and domU

On Wed, Nov 11, 2009 at 12:03:23AM +0300, Matthieu Patou
wrote:> Hello Jordi,
> I noticed the same problem and that''s pretty nasty on HVM host
running
> windows as the system can''t login on domain by defaut due to too
big
> time drift.
> 
> I worked around by adding ~ 6 minutes to the time of the domU at startup.
> 
Can you please paste your /etc/xen/<windowsguest> cfgfile.. let''s
see if
there''s something to tweak, related to that time problem.

-- Pasi


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Jordi Espasa Clofent

2009-Nov-11 10:01 UTC

head link

Re: [Xen-users] Time diferrence between dom0 and domU

> I just got answer from Jeremy Fitzhardinge to my questions regarding 
> timekeepeing sent to xen-devel. See: 
> http://lists.xensource.com/archives/html/xen-devel/2009-11/msg00505.html .
 From Jeremy''s word I understand that ntpd is always the best and 
prefered solution to keep up time sync.
> The good news for me is that it''s not that bad as I thought with
2.6.31.5
> kernels. Generally, xen makes dom0 and domU clocks go in lockstep with its 
> wallclock, but at the moment you cannot update xen wallclock from dom0 (nor
> from domU). When this feature is implemented, the problem should disappear
in
> 2.6.31+ kernels. Util that moment I''ll have to run ntpd in all
VMs. I think
> 200ms time difference, which I have under heavy load, is not a big issue.
Of
> course, that''s my point of view and your applications might be
more strict.
Good news.
> If you are interested in older kernels, please, join the discussion on xen-
> devel: http://lists.xensource.com/archives/html/xen-
> devel/2009-11/msg00469.html
Thanks to point me out.

;)

-- 
I must not fear. Fear is the mind-killer. Fear is the little-death that 
brings total obliteration. I will face my fear. I will permit it to pass 
over me and through me. And when it has gone past I will turn the inner 
eye to see its path. Where the fear has gone there will be nothing. Only 
I will remain.

Bene Gesserit Litany Against Fear.

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

Bartosz Lis

2009-Nov-12 09:11 UTC

head link

Re: [Xen-users] Time diferrence between dom0 and domU

Dnia wtorek, 10 listopada 2009 o 22:03:23 Matthieu Patou
napisał(a):> Hello Jordi,
> I noticed the same problem and that''s pretty nasty on HVM host
running
> windows as the system can''t login on domain by defaut due to too
big
> time drift.
> 
> I worked around by adding ~ 6 minutes to the time of the domU at startup.
> 
Matthieu,

It looks like your xen wallclock differs ~6 min from dom0 time. This 
difference may change slightly but noticeably after some time, say, a month. 
Better workaround would be synchronizing your windows to some NTP server. See 
the discussion on xen-devel: 

http://lists.xensource.com/archives/html/xen-devel/2009-11/msg00505.html 

Regards,

-- 
Bartosz Lis @ Inst. of Information Technology, Technical Univ. of Lodz, Poland
   bartoszl @ ics.p.lodz.pl

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Matthieu Patou

2009-Nov-13 15:59 UTC

head link

Re: [Xen-users] Time diferrence between dom0 and domU

On 11/11/2009 12:32, Pasi Kärkkäinen wrote:> On Wed, Nov 11, 2009 at 12:03:23AM +0300, Matthieu Patou wrote:
>    
>> Hello Jordi,
>> I noticed the same problem and that''s pretty nasty on HVM host
running
>> windows as the system can''t login on domain by defaut due to
too big
>> time drift.
>>
>> I worked around by adding ~ 6 minutes to the time of the domU at
startup.
>>
>>      
> Can you please paste your /etc/xen/<windowsguest>  cfgfile..
let''s see if
> there''s something to tweak, related to that time problem.
>
> -- PasiHere it is:

import os, re, time

arch = os.uname()[4]
if re.search(''64'', arch):
     arch_libdir = ''lib64''
else:
     arch_libdir = ''lib''

kernel = "/usr/lib/xen-3.2-1/boot/hvmloader"

builder=''hvm''
memory = 1500
shadow_memory = 16
name = "xen-w2k8"
vif = [ ''bridge=br1'' ]
disk = [ ''phy:/dev/vgxen/lvvz01_w2k8,hda'']
device_model = ''/usr/'' + arch_libdir +
''/xen-3.2-1/bin/qemu-dm''
# boot on floppy (a), hard disk (c) or CD-ROM (d)
# default: hard disk, cd-rom, floppy
boot="c"
acpi = 1
apic = 1
sdl=0
vnc=1
usb=1
#usbdevice=[ ''tablet'', ''host:04b9:0300'']
usbdevice=''tablet''
# Have to make a clever thing for daylight saving ...
rtc_timeoffset=-(time.altzone)
localtime=0
stdvga=0
vncconsole=1
vncpasswd=''chazam''
monitor=1
serial=''pty''
vncviewer = 0
vcpus = 2
cpus = ''2,3''
independent_wallclock = 1




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Matthieu Patou

2009-Nov-17 13:07 UTC

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Re: [Xen-users] Time diferrence between dom0 and domU

On 12/11/2009 12:11, Bartosz Lis wrote:> Dnia wtorek, 10 listopada 2009 o 22:03:23 Matthieu Patou napisał(a):
>> Hello Jordi,
>> I noticed the same problem and that''s pretty nasty on HVM host
running
>> windows as the system can''t login on domain by defaut due to
too big
>> time drift.
>>
>> I worked around by adding ~ 6 minutes to the time of the domU at
startup.
>>
>
> Matthieu,
>
> It looks like your xen wallclock differs ~6 min from dom0 time. This
> difference may change slightly but noticeably after some time, say, a
month.
> Better workaround would be synchronizing your windows to some NTP server.
See
> the discussion on xen-devel:
>
> http://lists.xensource.com/archives/html/xen-devel/2009-11/msg00505.html
>Hi Dnia,

Thanks  for the tips, I forgot to mention that this windows hvm is part 
of a domain so I already get the ntp synchronisation as Windows AD rely 
on very accurate clocks (<5minutes drift). So in the long run my clocks 
are in sync but the very few minutes after the boot without the 
rtc_timeoffset=-(time.altzone) + 6
I''ve a too big drift and the some stuff do not work properly (ie. 
startup script for workstation/server).

Note: I use time.altzone, as localtime = 1 is not working anymore for me 
(since xen 3.2).

Matthieu.

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Xen users - Nov 2009 - Time diferrence between dom0 and domU

[Xen-users] Time diferrence between dom0 and domU

[Xen-users] Time diferrence between dom0 and domU

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Re: [Xen-users] Time diferrence between dom0 and domU

Re: [Xen-users] Time diferrence between dom0 and domU

Re: [Xen-users] Time diferrence between dom0 and domU

Re: [Xen-users] Time diferrence between dom0 and domU

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Re: [Xen-users] Time diferrence between dom0 and domU

Re: [Xen-users] Time diferrence between dom0 and domU

Re: [Xen-users] Time diferrence between dom0 and domU

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Re: [Xen-users] Time diferrence between dom0 and domU

Re: [Xen-users] Time diferrence between dom0 and domU

Re: [Xen-users] Time diferrence between dom0 and domU

Re: [Xen-users] Time diferrence between dom0 and domU

Re: [Xen-users] Time diferrence between dom0 and domU

Re: [Xen-users] Time diferrence between dom0 and domU