Daniel Lam
2010-Jan-02 06:20 UTC
[Xen-users] Resolve "Time went backwards" problem by using jiffies as clocksource
Hi All,
I''m new to Xen and... Happy New Year!
After restarting dom-0, my dom-u prints this in console once every second,
[55082.616234] __ratelimit: 1503 messages suppressed
[55082.616234] clocksource/0: Time went backwards: ret=380ab26c53a
I resolved this by following the instructions in
"http://wiki.debian.org/Xen",
which is basically changing clocksource to "jiffies".
Now the problem has gone away, I''m wondering if somebody can help me:
1. Is domain-0 not able to set the system time of domain-u the root cause?
I can see this error in console "Unable to set System Clock to: <a
datetime value>",
even after I changed clocksource to "jiffies".
2. Why can''t domain-0 set the date of the domain-u?
3. If this is the only way to go (using jiffies clocksource), I will have to
sync
the domain-u system time manually using something like ntpd?
Thanks!
cheers,
Daniel
_______________________________________________
Xen-users mailing list
Xen-users@lists.xensource.com
http://lists.xensource.com/xen-users
Daniel Lam
2010-Jan-03 16:44 UTC
Re: [Xen-users] Resolve "Time went backwards" problem by using jiffies as clocksource
Hi All - so I guess nobody has the answers to these questions?
Is there somewhere I can ask, perhaps the developers list?
Daniel
---------- Forwarded message ----------
From: Daniel Lam <daniel@rockableapps.com>
To: xen-users@lists.xensource.com
Date: Sat, 2 Jan 2010 17:20:12 +1100
Subject: [Xen-users] Resolve "Time went backwards" problem by using
jiffies
as clocksource
Hi All,
I''m new to Xen and... Happy New Year!
After restarting dom-0, my dom-u prints this in console once every second,
[55082.616234] __ratelimit: 1503 messages suppressed
[55082.616234] clocksource/0: Time went backwards: ret=380ab26c53a
I resolved this by following the instructions in
"http://wiki.debian.org/Xen
",
which is basically changing clocksource to "jiffies".
Now the problem has gone away, I''m wondering if somebody can help me:
1. Is domain-0 not able to set the system time of domain-u the root cause?
I can see this error in console "Unable to set System Clock to: <a
datetime value>",
even after I changed clocksource to "jiffies".
2. Why can''t domain-0 set the date of the domain-u?
3. If this is the only way to go (using jiffies clocksource), I will have to
sync
the domain-u system time manually using something like ntpd?
Thanks!
cheers,
Daniel
_______________________________________________
Xen-users mailing list
Xen-users@lists.xensource.com
http://lists.xensource.com/xen-users
Pasi Kärkkäinen
2010-Jan-03 16:49 UTC
Re: [Xen-users] Resolve "Time went backwards" problem by using jiffies as clocksource
On Mon, Jan 04, 2010 at 03:44:34AM +1100, Daniel Lam wrote:> Hi All - so I guess nobody has the answers to these questions? > Is there somewhere I can ask, perhaps the developers list? >Have you tried using newer Xen hypervisor? Xen 3.4.2 is the latest stable release. Also, did you try different dom0/domU kernel versions? -- Pasi> Daniel > ---------- Forwarded message ---------- > From: Daniel Lam <[1]daniel@rockableapps.com> > To: [2]xen-users@lists.xensource.com > Date: Sat, 2 Jan 2010 17:20:12 +1100 > Subject: [Xen-users] Resolve "Time went backwards" problem by using > jiffies as clocksource > Hi All, > I''m new to Xen and... Happy New Year! > After restarting dom-0, my dom-u prints this in console once every second, > [55082.616234] __ratelimit: 1503 messages suppressed > [55082.616234] clocksource/0: Time went backwards: ret=380ab26c53a > I resolved this by following the instructions in > "[3]http://wiki.debian.org/Xen", > which is basically changing clocksource to "jiffies". > Now the problem has gone away, I''m wondering if somebody can help me: > 1. Is domain-0 not able to set the system time of domain-u the root cause? > I can see this error in console "Unable to set System Clock to: <a > datetime value>", > even after I changed clocksource to "jiffies". > 2. Why can''t domain-0 set the date of the domain-u? > 3. If this is the only way to go (using jiffies clocksource), I will have > to sync > the domain-u system time manually using something like ntpd? > Thanks! > cheers, > Daniel > > References > > Visible links > 1. mailto:daniel@rockableapps.com > 2. mailto:xen-users@lists.xensource.com > 3. http://wiki.debian.org/Xen> _______________________________________________ > Xen-users mailing list > Xen-users@lists.xensource.com > http://lists.xensource.com/xen-users_______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users
Daniel Lam
2010-Jan-03 16:56 UTC
Re: [Xen-users] Resolve "Time went backwards" problem by using jiffies as clocksource
On Mon, Jan 4, 2010 at 3:49 AM, Pasi Kärkkäinen <pasik@iki.fi> wrote:> On Mon, Jan 04, 2010 at 03:44:34AM +1100, Daniel Lam wrote: > > Hi All - so I guess nobody has the answers to these questions? > > Is there somewhere I can ask, perhaps the developers list? > > > > Have you tried using newer Xen hypervisor? > Xen 3.4.2 is the latest stable release. > > Also, did you try different dom0/domU kernel versions? > > -- Pasi > >Thanks for prompt reply. I *think* I have the latest stable version - I installed Xen by running apt-get install xen-linux-system-2.6.26-2-xen-686 on Debian 5.0 Lenny. And no I haven''t tried different dom0/domU kernel versions. I have only been playing around with Debian 5.0 Lenny, as dom0 and domU. Are you suggesting that using xen as clocksource should work on latest stable versions? And for the record I''m experimenting on a Dell Optiplex GX520 with 2gb ram. Daniel> Daniel > > ---------- Forwarded message ---------- > > From: Daniel Lam <[1]daniel@rockableapps.com> > > To: [2]xen-users@lists.xensource.com > > Date: Sat, 2 Jan 2010 17:20:12 +1100 > > Subject: [Xen-users] Resolve "Time went backwards" problem by using > > jiffies as clocksource > > Hi All, > > I''m new to Xen and... Happy New Year! > > After restarting dom-0, my dom-u prints this in console once every > second, > > [55082.616234] __ratelimit: 1503 messages suppressed > > [55082.616234] clocksource/0: Time went backwards: ret=380ab26c53a > > I resolved this by following the instructions in > > "[3]http://wiki.debian.org/Xen", > > which is basically changing clocksource to "jiffies". > > Now the problem has gone away, I''m wondering if somebody can help me: > > 1. Is domain-0 not able to set the system time of domain-u the root > cause? > > I can see this error in console "Unable to set System Clock to: <a > > datetime value>", > > even after I changed clocksource to "jiffies". > > 2. Why can''t domain-0 set the date of the domain-u? > > 3. If this is the only way to go (using jiffies clocksource), I will > have > > to sync > > the domain-u system time manually using something like ntpd? > > Thanks! > > cheers, > > Daniel > > > > References > > > > Visible links > > 1. mailto:daniel@rockableapps.com > > 2. mailto:xen-users@lists.xensource.com > > 3. http://wiki.debian.org/Xen > > > _______________________________________________ > > Xen-users mailing list > > Xen-users@lists.xensource.com > > http://lists.xensource.com/xen-users >_______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users
Matthew Law
2010-Jan-03 17:06 UTC
Re: [Xen-users] Resolve "Time went backwards" problem by using jiffies as clocksource
Hi Daniel, I''m sure someone has the answer - just not likely to arrive to quickly at this time of year and a weekend ;-) I ran in to this too (I''m a relative Xen newbie) and my experience of this bug is that it is a problem which is inherent in the xenified debian kernels. They appear to use some of the backports from opensuse and there appears to be an issue with the way they have been used in debian which means the kernel clock sync doesn''t work properly. You can detach the clock sync from the dom0 and do it in the domU with ntp (as per the debain wiki doc) or, build your own kernel using the vanilla xen kernel sources (which works, but is a pain). I opted for the former. I get the impression that this won''t be fixed for a while in debian stable as, like so many others, they are concentrating on kvm over xen. There may be other options. I am sure others will chime in if there are. Good luck, Matt. On Sun, January 3, 2010 4:56 pm, Daniel Lam wrote:> On Mon, Jan 4, 2010 at 3:49 AM, Pasi Kärkkäinen <pasik@iki.fi> wrote: > >> On Mon, Jan 04, 2010 at 03:44:34AM +1100, Daniel Lam wrote: >> > Hi All - so I guess nobody has the answers to these questions? >> > Is there somewhere I can ask, perhaps the developers list? >> > >> >> Have you tried using newer Xen hypervisor? >> Xen 3.4.2 is the latest stable release. >> >> Also, did you try different dom0/domU kernel versions? >> >> -- Pasi >> >> > Thanks for prompt reply. > > I *think* I have the latest stable version - I installed Xen by running > > apt-get install xen-linux-system-2.6.26-2-xen-686 > > on Debian 5.0 Lenny. And no I haven''t tried different dom0/domU > kernel versions. I have only been playing around with Debian 5.0 Lenny, > as dom0 and domU. > > Are you suggesting that using xen as clocksource should work > on latest stable versions? > > And for the record I''m experimenting on a Dell Optiplex GX520 with 2gb > ram. > > Daniel > >> Daniel >> > ---------- Forwarded message ---------- >> > From: Daniel Lam <[1]daniel@rockableapps.com> >> > To: [2]xen-users@lists.xensource.com >> > Date: Sat, 2 Jan 2010 17:20:12 +1100 >> > Subject: [Xen-users] Resolve "Time went backwards" problem by using >> > jiffies as clocksource >> > Hi All, >> > I''m new to Xen and... Happy New Year! >> > After restarting dom-0, my dom-u prints this in console once every >> second, >> > [55082.616234] __ratelimit: 1503 messages suppressed >> > [55082.616234] clocksource/0: Time went backwards: ret=380ab26c53a >> > I resolved this by following the instructions in >> > "[3]http://wiki.debian.org/Xen", >> > which is basically changing clocksource to "jiffies". >> > Now the problem has gone away, I''m wondering if somebody can help >> me: >> > 1. Is domain-0 not able to set the system time of domain-u the root >> cause? >> > I can see this error in console "Unable to set System Clock to: >> <a >> > datetime value>", >> > even after I changed clocksource to "jiffies". >> > 2. Why can''t domain-0 set the date of the domain-u? >> > 3. If this is the only way to go (using jiffies clocksource), I >> will >> have >> > to sync >> > the domain-u system time manually using something like ntpd? >> > Thanks! >> > cheers, >> > Daniel >> > >> > References >> > >> > Visible links >> > 1. mailto:daniel@rockableapps.com >> > 2. mailto:xen-users@lists.xensource.com >> > 3. http://wiki.debian.org/Xen_______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users
Pasi Kärkkäinen
2010-Jan-03 17:11 UTC
Re: [Xen-users] Resolve "Time went backwards" problem by using jiffies as clocksource
On Mon, Jan 04, 2010 at 03:56:46AM +1100, Daniel Lam wrote:> On Mon, Jan 4, 2010 at 3:49 AM, Pasi Kärkkäinen <[1]pasik@iki.fi> wrote: > > On Mon, Jan 04, 2010 at 03:44:34AM +1100, Daniel Lam wrote: > > Hi All - so I guess nobody has the answers to these questions? > > Is there somewhere I can ask, perhaps the developers list? > > > > Have you tried using newer Xen hypervisor? > Xen 3.4.2 is the latest stable release. > > Also, did you try different dom0/domU kernel versions? > > -- Pasi > > Thanks for prompt reply. > I *think* I have the latest stable version - I installed Xen by running > apt-get install xen-linux-system-2.6.26-2-xen-686 > on Debian 5.0 Lenny. >So you have the latest version included in *Lenny*, which is already pretty old. The Xen hypervisor in lenny is version 3.2, which is pretty old. Like said, the newest stable upstream Xen version is 3.4.2. Also the Xen dom0 kernel in lenny is based on some early opensuse kernel snapshot, and it''s known to have problems/bugs.> And no I haven''t tried different dom0/domU > kernel versions. I have only been playing around with Debian 5.0 Lenny, > as dom0 and domU. > Are you suggesting that using xen as clocksource should work > on latest stable versions? > And for the record I''m experimenting on a Dell Optiplex GX520 with 2gb > ram.It should work yeah, and you shouldn''t have "time went backwards" errors. -- Pasi _______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users
Daniel Lam
2010-Jan-03 17:13 UTC
Re: [Xen-users] Resolve "Time went backwards" problem by using jiffies as clocksource
On Mon, Jan 4, 2010 at 4:11 AM, Pasi Kärkkäinen <pasik@iki.fi> wrote:> On Mon, Jan 04, 2010 at 03:56:46AM +1100, Daniel Lam wrote: > > On Mon, Jan 4, 2010 at 3:49 AM, Pasi Kärkkäinen <[1]pasik@iki.fi> > wrote: > > > > On Mon, Jan 04, 2010 at 03:44:34AM +1100, Daniel Lam wrote: > > > Hi All - so I guess nobody has the answers to these questions? > > > Is there somewhere I can ask, perhaps the developers list? > > > > > > > Have you tried using newer Xen hypervisor? > > Xen 3.4.2 is the latest stable release. > > > > Also, did you try different dom0/domU kernel versions? > > > > -- Pasi > > > > Thanks for prompt reply. > > I *think* I have the latest stable version - I installed Xen by > running > > apt-get install xen-linux-system-2.6.26-2-xen-686 > > on Debian 5.0 Lenny. > > > > So you have the latest version included in *Lenny*, which is already > pretty old. > > The Xen hypervisor in lenny is version 3.2, which is pretty old. Like said, > the newest stable upstream Xen version is 3.4.2. Also the Xen > dom0 kernel in lenny is based on some early opensuse kernel snapshot, > and it''s known to have problems/bugs. > > > And no I haven''t tried different dom0/domU > > kernel versions. I have only been playing around with Debian 5.0 > Lenny, > > as dom0 and domU. > > Are you suggesting that using xen as clocksource should work > > on latest stable versions? > > And for the record I''m experimenting on a Dell Optiplex GX520 with 2gb > > ram. > > It should work yeah, and you shouldn''t have "time went backwards" > errors. > > -- Pasi > >Thanks.. got it! Again thanks for prompt reply! Daniel _______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users
Daniel Lam
2010-Jan-03 17:24 UTC
Re: [Xen-users] Resolve "Time went backwards" problem by using jiffies as clocksource
On Mon, Jan 4, 2010 at 4:06 AM, Matthew Law <matt@webcontracts.co.uk> wrote:> Hi Daniel, > > I''m sure someone has the answer - just not likely to arrive to quickly at > this time of year and a weekend ;-) > > I ran in to this too (I''m a relative Xen newbie) and my experience of this > bug is that it is a problem which is inherent in the xenified debian > kernels. They appear to use some of the backports from opensuse and there > appears to be an issue with the way they have been used in debian which > means the kernel clock sync doesn''t work properly. > > You can detach the clock sync from the dom0 and do it in the domU with ntp > (as per the debain wiki doc) or, build your own kernel using the vanilla > xen kernel sources (which works, but is a pain). I opted for the former. > I get the impression that this won''t be fixed for a while in debian stable > as, like so many others, they are concentrating on kvm over xen. > > There may be other options. I am sure others will chime in if there are. > > Good luck, > > Matt. > >Thanks for your prompt but detail reply! True true.. still in the new year mood.. Your reply totally concurs with Pasi''s and they make sense now. As a side question - which distro concentrates on Xen more? (if there is one) Fedora Core is out of the question now, Ubuntu 9.10 installation is a pain for some reason, I thought Debian would be the next best choice - now hearing what you guys said, I''m wondering if there is a better option (In the sense that I can rely on the built-in xen package without touching the kernel myself). Daniel _______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users
Matthew Law
2010-Jan-03 17:56 UTC
Re: [Xen-users] Resolve "Time went backwards" problem by using jiffies as clocksource
You''re welcome. I''m not 100% sure the clock source fix actually works that well and it also raises the issue that every domU which syncs it''s own clock is using more CPU time than one that doesn''t. Not a lot more, but more nonetheless. Also you''ll notice when you startup the recommended xen domU it will raise some errors about modules failing to work. If you compile your own you can get a much better domU but it is more work. I''m not sure you can say any distro concentrates more. I suppose you could argue that Citrix''s XenServer is the best option if you want a no-hassle Xen option. I''ve never used it because I have invested time and money in developing my own tools for my own customers. Others I know use it and really like it - choice is a good thing (tm). I currently use CentOS for my dom0 with Xen installed either from source or using the Gitco Xen repository. Given the choice I would use debian as my distro of choice, but as you''ve already heard the Xen implementation in Lenny is awful -most out of character for debian, imho. I used CentOS because it was the next best option. I haven''t tried any other distro. I am keeping a very close eye on OpenSolaris. The combo of ZFS, their Crossbow network virtualisation and Xen (or XVM in Sun marketing speak) has a lot of promise. Throw in their OpenHA cluster and the other enterprisey stuff you can do with solaris and it could be very good. Once there is a release version of OpenSolaris with a Sun support option (and the whole Oracle takeover thing is sorted) I may well jump. Its not production ready yet though. HTH, Matt. On Sun, January 3, 2010 5:24 pm, Daniel Lam wrote:> Thanks for your prompt but detail reply! True true.. still in the new year > mood.. > > Your reply totally concurs with Pasi''s and they make sense now. > > As a side question - which distro concentrates on Xen more? (if there is > one) > > Fedora Core is out of the question now, Ubuntu 9.10 installation is a pain > for some reason, > I thought Debian would be the next best choice - now hearing what you guys > said, > I''m wondering if there is a better option (In the sense that I can rely > on > the built-in > xen package without touching the kernel myself). > > Daniel_______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users