Dear Xen users,

After some experiencing, I've found a soultion to my problem, I just share it with you, and hope you wont get issues that I got.


Maybe, all experience is just true for my hardware, but it is not a special one, it is a Supermicro PDSMi-LN4 board with a Q6700. I think other parameters do not affect.

I had problems with time skews in the domU's, particularly with freebsd systems. With HVM instances, hpet should be enabled for the vm, as it keeps time ticking very precise. But I had issues, that caused time jumps in a short time, and I've found it was related to the dom0's kernel message 'Clocksoure tsc unstable'. So then, I've started my xen hypervisor with clocksource=pit, and since then (around 1 week) I do not experience such time jumps, or time skews.

Regards,


Kojedzinszky Richard
Euronet Magyarorszag Informatikai Zrt.

On Mon, 13 Aug 2012, Richard Kojedzinszky wrote:

Date: Mon, 13 Aug 2012 10:08:29 +0200 (CEST)
From: Richard Kojedzinszky <kri...@tvnetwork.hu>
To: freebsd-xen@freebsd.org
Subject: Re: time jumps in xen amd64/hvm instance

Dear developers/users,

I am still facing with time jump problems. Did somebody detect same issues, or only I am doing something wrong. My dom0 is a debian squeeze, my domU is a freebsd-9.0, amd64, kernel compiled by myself.

Currently I cannot find the exact steps needed to reproduce the problem, but unfortunately it happens. Actually, in the past weekend it did also, when the server had lower load than in workdays.

Where should I look further? Any ideas?

Thanks,

Kojedzinszky Richard
Euronet Magyarorszag Informatikai Zrt.

On Tue, 10 Jul 2012, Richard Kojedzinszky wrote:

Date: Tue, 10 Jul 2012 20:57:09 +0200 (CEST)
From: Richard Kojedzinszky <kri...@tvnetwork.hu>
To: freebsd-xen@freebsd.org
Subject: Re: time jumps in xen amd64/hvm instance


just an update, as I remember, this happened to 8.2 bsd in paravirtualized mode also.


Kojedzinszky Richard
Euronet Magyarorszag Informatikai Zrt.

On Mon, 9 Jul 2012, Richard Kojedzinszky wrote:

Date: Mon, 9 Jul 2012 21:10:52 +0200 (CEST)
From: Richard Kojedzinszky <kri...@tvnetwork.hu>
To: freebsd-xen@freebsd.org
Subject: time jumps in xen amd64/hvm instance

Dear Xen users,

I have a strange problem, my hvm instance sometimes jumps time forward. I made a little script to monitor this, and I am attaching its result also. I have no clues where to look, why this jump happens, but of course it is not normal. And as I have kern.securelevel at 2, ntp cannot correct this.

Could somebody help?

The amd64hvmntp.sh script is run by cron every minute.

Thanks in advance,

Kojedzinszky Richard
Euronet Magyarorszag Informatikai Zrt.
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