[opensuse-virtual] Leap 42.2 + Xen: Missing Independent Wallclock

Rieß Norman

22 Nov 2016 22 Nov '16

06:50

Hello, i just installed our first Leap 42.2 DomU and as i wanted to adapt our usual scriptset i noticed, that the settings for independent wallclock seem to be missing. While the doc is stating that independent wallclock settings should apply for Leap 42.2, /proc/sys/xen is not showing the appropriate file. /proc/sys/xen # ls balloon Has something gone wrong during installation, or is the documentation faulty? Regards, Norman Doc: https://doc.opensuse.org/documentation/leap/virtualization/html/book.virt/se... To unsubscribe, e-mail: opensuse-virtual+unsubscribe@opensuse.org To contact the owner, e-mail: opensuse-virtual+owner@opensuse.org

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Jan Beulich

22 Nov 22 Nov

09:08

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On 22.11.16 at 07:50, wrote: i just installed our first Leap 42.2 DomU and as i wanted to adapt our usual scriptset i noticed, that the settings for independent wallclock seem to be missing. While the doc is stating that independent wallclock settings should apply for Leap 42.2, /proc/sys/xen is not showing the appropriate file.

/proc/sys/xen # ls balloon

Has something gone wrong during installation, or is the documentation faulty?

I don't think the pv-ops kernel has ever supported the concept of independent wallclock as configurable behavior. If you observe any misbehavior without it, please open a bug. Jan -- To unsubscribe, e-mail: opensuse-virtual+unsubscribe@opensuse.org To contact the owner, e-mail: opensuse-virtual+owner@opensuse.org

Per Jessen

24 Nov 24 Nov

12:51

Jan Beulich wrote:

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On 22.11.16 at 07:50, wrote: i just installed our first Leap 42.2 DomU and as i wanted to adapt our usual scriptset i noticed, that the settings for independent wallclock seem to be missing. While the doc is stating that independent wallclock settings should apply for Leap 42.2, /proc/sys/xen is not showing the appropriate file.

/proc/sys/xen # ls balloon

Has something gone wrong during installation, or is the documentation faulty?

I don't think the pv-ops kernel has ever supported the concept of independent wallclock as configurable behavior. If you observe any misbehavior without it, please open a bug.

We started switching to independent wallclock when systemd was introduced - systemd kept complaining about the clock being adjusted or something like that. After a lot of research, we switched to using independent_wallclock for all guests. Afair, this was/is also the SUSE/Novell recommendation. -- Per Jessen, Zürich (10.1°C) -- To unsubscribe, e-mail: opensuse-virtual+unsubscribe@opensuse.org To contact the owner, e-mail: opensuse-virtual+owner@opensuse.org

Jan Beulich

13:19

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On 24.11.16 at 13:51, wrote: Jan Beulich wrote:

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On 22.11.16 at 07:50, wrote: i just installed our first Leap 42.2 DomU and as i wanted to adapt our usual scriptset i noticed, that the settings for independent wallclock seem to be missing. While the doc is stating that independent wallclock settings should apply for Leap 42.2, /proc/sys/xen is not showing the appropriate file.

/proc/sys/xen # ls balloon

Has something gone wrong during installation, or is the documentation faulty?

I don't think the pv-ops kernel has ever supported the concept of independent wallclock as configurable behavior. If you observe any misbehavior without it, please open a bug.

We started switching to independent wallclock when systemd was introduced - systemd kept complaining about the clock being adjusted or something like that.

Over time we had kernel problems in that area, so much would depend on when exactly you found it necessary to switch. Also I don't think your reply really demonstrates any observed misbehavior with the pv-ops kernel, yet that's the only criteria based upon which fixing that kernel or considering to re-introduce that control would become possible routes forward.

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After a lot of research, we switched to using independent_wallclock for all guests. Afair, this was/is also the SUSE/Novell recommendation.

Not as far as I know. As long as there are no bugs, running e.g. NTP once in Dom0 would seem the more efficient model compared to running it in every DomU. But of course I don't know who gave this recommendation, and in which context that was. Jan -- To unsubscribe, e-mail: opensuse-virtual+unsubscribe@opensuse.org To contact the owner, e-mail: opensuse-virtual+owner@opensuse.org

Per Jessen

14:05

Jan Beulich wrote:

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On 24.11.16 at 13:51, wrote: Jan Beulich wrote:

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On 22.11.16 at 07:50, wrote: i just installed our first Leap 42.2 DomU and as i wanted to adapt our usual scriptset i noticed, that the settings for independent wallclock seem to be missing. While the doc is stating that independent wallclock settings should apply for Leap 42.2, /proc/sys/xen is not showing the appropriate file.

/proc/sys/xen # ls balloon

Has something gone wrong during installation, or is the documentation faulty?

I don't think the pv-ops kernel has ever supported the concept of independent wallclock as configurable behavior. If you observe any misbehavior without it, please open a bug.

We started switching to independent wallclock when systemd was introduced - systemd kept complaining about the clock being adjusted or something like that.

Over time we had kernel problems in that area, so much would depend on when exactly you found it necessary to switch.

Judging by my mailing list postings, I think we started in March 2015. https://lists.opensuse.org/opensuse-virtual/2015-03/msg00020.html

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Also I don't think your reply really demonstrates any observed misbehavior with the pv-ops kernel, yet that's the only criteria based upon which fixing that kernel or considering to re-introduce that control would become possible routes forward.

We observed ntp-related poor behaviour by systemd, that's all. Hundreds of message being written about "Time has been changed". Switching to local ntp and independent wallclock solved the issue.

...

...
After a lot of research, we switched to using independent_wallclock for all guests. Afair, this was/is also the SUSE/Novell recommendation.

Not as far as I know. As long as there are no bugs, running e.g. NTP once in Dom0 would seem the more efficient model compared to running it in every DomU. But of course I don't know who gave this recommendation, and in which context that was.

http://www.novell.com/documentation/vmserver/config_options/data/b9qzhq5.htm... https://doc.opensuse.org/documentation/leap/virtualization/html/book.virt/se... "To effectively use an external time source, such as NTP, for time synchronization on a virtual machine, the virtual machine's independent wallclock setting must be enabled (set to 1)." Perhaps not a recommendation, but given that systemd didn't like the domU just relying on the Dom0 clock, using running ntp in the DomU and enabling independent wallclock was a solution. https://wiki.debian.org/Xen/Clocksource https://lists.opensuse.org/opensuse-virtual/2015-03/msg00022.html I remember finding it very difficult to get any solid information on this topic. -- Per Jessen, Zürich (9.9°C) -- To unsubscribe, e-mail: opensuse-virtual+unsubscribe@opensuse.org To contact the owner, e-mail: opensuse-virtual+owner@opensuse.org

Rieß Norman

29 Nov 29 Nov

07:29

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Am 24.11.2016 um 15:05 schrieb Per Jessen :

Jan Beulich wrote:

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On 24.11.16 at 13:51, wrote: Jan Beulich wrote:

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> On 22.11.16 at 07:50, wrote: i just installed our first Leap 42.2 DomU and as i wanted to adapt our usual scriptset i noticed, that the settings for independent wallclock seem to be missing. While the doc is stating that independent wallclock settings should apply for Leap 42.2, /proc/sys/xen is not showing the appropriate file.

/proc/sys/xen # ls balloon

Has something gone wrong during installation, or is the documentation faulty?

I don't think the pv-ops kernel has ever supported the concept of independent wallclock as configurable behavior. If you observe any misbehavior without it, please open a bug.

We started switching to independent wallclock when systemd was introduced - systemd kept complaining about the clock being adjusted or something like that.

Over time we had kernel problems in that area, so much would depend on when exactly you found it necessary to switch.

Judging by my mailing list postings, I think we started in March 2015. https://lists.opensuse.org/opensuse-virtual/2015-03/msg00020.html

...
Also I don't think your reply really demonstrates any observed misbehavior with the pv-ops kernel, yet that's the only criteria based upon which fixing that kernel or considering to re-introduce that control would become possible routes forward.

We observed ntp-related poor behaviour by systemd, that's all. Hundreds of message being written about "Time has been changed". Switching to local ntp and independent wallclock solved the issue.

...
...
After a lot of research, we switched to using independent_wallclock for all guests. Afair, this was/is also the SUSE/Novell recommendation.

Not as far as I know. As long as there are no bugs, running e.g. NTP once in Dom0 would seem the more efficient model compared to running it in every DomU. But of course I don't know who gave this recommendation, and in which context that was.

http://www.novell.com/documentation/vmserver/config_options/data/b9qzhq5.htm... https://doc.opensuse.org/documentation/leap/virtualization/html/book.virt/se...

"To effectively use an external time source, such as NTP, for time synchronization on a virtual machine, the virtual machine's independent wallclock setting must be enabled (set to 1)."

Perhaps not a recommendation, but given that systemd didn't like the domU just relying on the Dom0 clock, using running ntp in the DomU and enabling independent wallclock was a solution.

https://wiki.debian.org/Xen/Clocksource https://lists.opensuse.org/opensuse-virtual/2015-03/msg00022.html

I remember finding it very difficult to get any solid information on this topic.

-- Per Jessen, Zürich (9.9°C)

Hello, we started using independent wallclock because the little timejump while live migrating was sufficient to disrupt some time dependent services. All our hosts (and VMs) use NTP, but the drift seems to be enough. Setting independent wallclock solved this behaviour. Because this is in allignment with the official documentation, we never considered this to be a problem. Norman, Offenbach (-7°C) :-)

Olaf Hering

07:48

On Tue, Nov 29, Rieß Norman wrote:

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we started using independent wallclock because the little timejump while live migrating was sufficient to disrupt some time dependent services. All our hosts (and VMs) use NTP, but the drift seems to be enough. Setting independent wallclock solved this behaviour.

Are you saying that even with correctly running ntpd in both dom0s the migrated domU will see a timejump? A small jump forward is expected because the domU goes through a suspend/resume cycle while the last pages of dirty memory get transfered. I would be surprised if independent wallclock can change anything in this regard. Olaf

Rieß Norman

08:51

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Am 29.11.2016 um 08:48 schrieb Olaf Hering :

On Tue, Nov 29, Rieß Norman wrote:

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we started using independent wallclock because the little timejump while live migrating was sufficient to disrupt some time dependent services. All our hosts (and VMs) use NTP, but the drift seems to be enough. Setting independent wallclock solved this behaviour.

Are you saying that even with correctly running ntpd in both dom0s the migrated domU will see a timejump? A small jump forward is expected because the domU goes through a suspend/resume cycle while the last pages of dirty memory get transfered. I would be surprised if independent wallclock can change anything in this regard.

Olaf

Well, yes. This was the case several years ago. As the problem disappeared with the use of independent wallclock, we did not investigate in later releases. Norman

Jim Fehlig

15:40

Rieß Norman wrote:

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Am 29.11.2016 um 08:48 schrieb Olaf Hering :

On Tue, Nov 29, Rieß Norman wrote:

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we started using independent wallclock because the little timejump while live migrating was sufficient to disrupt some time dependent services. All our hosts (and VMs) use NTP, but the drift seems to be enough. Setting independent wallclock solved this behaviour. Are you saying that even with correctly running ntpd in both dom0s the migrated domU will see a timejump? A small jump forward is expected because the domU goes through a suspend/resume cycle while the last pages of dirty memory get transfered. I would be surprised if independent wallclock can change anything in this regard.

Olaf

Well, yes. This was the case several years ago. As the problem disappeared with the use of independent wallclock, we did not investigate in later releases.

To summarize the takeaway from this thread: The independent_wallclock control does not exist in the pvops kernel. If absence of this control causes problems, please enter a bug with the details. Regards, Jim -- To unsubscribe, e-mail: opensuse-virtual+unsubscribe@opensuse.org To contact the owner, e-mail: opensuse-virtual+owner@opensuse.org

Rieß Norman

30 Nov 30 Nov

06:02

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Am 29.11.2016 um 16:40 schrieb Jim Fehlig :

Rieß Norman wrote:

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Am 29.11.2016 um 08:48 schrieb Olaf Hering :

On Tue, Nov 29, Rieß Norman wrote:

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we started using independent wallclock because the little timejump while live migrating was sufficient to disrupt some time dependent services. All our hosts (and VMs) use NTP, but the drift seems to be enough. Setting independent wallclock solved this behaviour. Are you saying that even with correctly running ntpd in both dom0s the migrated domU will see a timejump? A small jump forward is expected because the domU goes through a suspend/resume cycle while the last pages of dirty memory get transfered. I would be surprised if independent wallclock can change anything in this regard.

Olaf

Well, yes. This was the case several years ago. As the problem disappeared with the use of independent wallclock, we did not investigate in later releases.

To summarize the takeaway from this thread: The independent_wallclock control does not exist in the pvops kernel. If absence of this control causes problems, please enter a bug with the details.

Regards, Jim

You should update your documentation then. Norman N��r��y隊Z)z{.��ۚ�맲��r��z�^�ˬz��N�(�֜��^� ޭ隊Z)z{.��ۚ��0��Ǩ�

Jim Fehlig

14:30

On 11/29/2016 11:02 PM, Rieß Norman wrote:

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Am 29.11.2016 um 16:40 schrieb Jim Fehlig :

Rieß Norman wrote:

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Am 29.11.2016 um 08:48 schrieb Olaf Hering :

On Tue, Nov 29, Rieß Norman wrote:

...
we started using independent wallclock because the little timejump while live migrating was sufficient to disrupt some time dependent services. All our hosts (and VMs) use NTP, but the drift seems to be enough. Setting independent wallclock solved this behaviour. Are you saying that even with correctly running ntpd in both dom0s the migrated domU will see a timejump? A small jump forward is expected because the domU goes through a suspend/resume cycle while the last pages of dirty memory get transfered. I would be surprised if independent wallclock can change anything in this regard.

Olaf

Well, yes. This was the case several years ago. As the problem disappeared with the use of independent wallclock, we did not investigate in later releases.

To summarize the takeaway from this thread: The independent_wallclock control does not exist in the pvops kernel. If absence of this control causes problems, please enter a bug with the details.

Regards, Jim

You should update your documentation then.

Yep. If you care to contribute to openSUSE, patches welcome :-). Regards, Jim -- To unsubscribe, e-mail: opensuse-virtual+unsubscribe@opensuse.org To contact the owner, e-mail: opensuse-virtual+owner@opensuse.org

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Jan Beulich
Jim Fehlig
Olaf Hering
Per Jessen
Rieß Norman

[opensuse-virtual] Leap 42.2 + Xen: Missing Independent Wallclock

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