WARNING - OLD ARCHIVES

This is an archived copy of the Xen.org mailing list, which we have preserved to ensure that existing links to archives are not broken. The live archive, which contains the latest emails, can be found at http://lists.xen.org/
   
 
 
Xen 
 
Home Products Support Community News
 
   
 

xen-users

Re: [Xen-users] Clock drift

To: xen-users@xxxxxxxxxxxxxxxxxxx
Subject: Re: [Xen-users] Clock drift
From: Antibozo <xen-users@xxxxxxxxxxxx>
Date: Mon, 25 Aug 2008 17:49:32 +0000
Delivery-date: Mon, 25 Aug 2008 10:50:10 -0700
Envelope-to: www-data@xxxxxxxxxxxxxxxxxxx
In-reply-to: <48B2E62B.6080103@xxxxxxx>
List-help: <mailto:xen-users-request@lists.xensource.com?subject=help>
List-id: Xen user discussion <xen-users.lists.xensource.com>
List-post: <mailto:xen-users@lists.xensource.com>
List-subscribe: <http://lists.xensource.com/mailman/listinfo/xen-users>, <mailto:xen-users-request@lists.xensource.com?subject=subscribe>
List-unsubscribe: <http://lists.xensource.com/mailman/listinfo/xen-users>, <mailto:xen-users-request@lists.xensource.com?subject=unsubscribe>
References: <a0f22fc90808151859v18361528nd1d185eeefba32c3@xxxxxxxxxxxxxx> <48AF925C.2050701@xxxxxxxxxxxx> <48B2E62B.6080103@xxxxxxx>
Sender: xen-users-bounces@xxxxxxxxxxxxxxxxxxx
User-agent: Mozilla/4.0 (compatible;MSIE 5.5; Windows 98)
On 2008-08-25 17:04, Eric Ross wrote:
Did you look into setting your clocksource to jiffies, that seemed to
help with my live migration issues.

Explicitly setting clocksource to jiffies made things worse if anything. IIRC it was the default anyway in most cases.

I struggled with time drift for months, I was running the same
configuration you were (except I didn't have any HVMs).  Then I tried
the following:

Dom0:
 independent wallclock = 1
 ntpd
 clocksource = jiffies

DomU:
 independent wallclock = 0
 clocksource = jiffies

I've been monitoring my Dom0s and DomUs with Hyperic for a few months
(specifically looking at ntp drift) and these settings produce the
closest numbers to a "bare metal" machine in my environment.

As I say, my problem is under control. independent_wallclock anywhere possible, acpi off on HVMs, ntpd everywhere. Only bummer is HVMs don't shut down all the way without acpi.

Top posting sucks.

Jefferson Ogata wrote:
On 2008-08-16 01:59, Ray Fadaie wrote:
I am using Xen on a Quad Core Phenom with 8G of RAM. Everything is
fine except the clock! [oh god :((]
In Dom0 everything works just fine but in DomUs the clock (both system
time and the realtime clock (IRQ8) drift. I can live with the system
time drift (I just enforce NTP every 5 minutes) but all my
applications in DomUs that depend on the realtime clock (IRQ8) are
messed up.
Do you guys have any idea what could be wrong here?

p.s. All DomUs and Dom0 are running CentOS 5 on on a M3A mother board
from Assus (64 bit CPU - X4).
I don't understand *why* this happens, but I've seen the same thing, as
have many others (check Google).

I think I've got it under control now. The following works for me:

On dom0:
- Set xen.independent_wallclock = 1 in /etc/sysctl.conf (corresponding
to /proc/sys/xen/independent_wallclock)
- Run ntpd.

On PVM domUs:
- Set xen.independent_wallclock = 1 in /etc/sysctl.conf
- Run ntpd.

On HVM domUs:
- Disable acpi in xen config (acpi = 0).
- Run ntpd.

The clock sometimes still jumps a bit during a live migration, but ntpd
slews it back afterward.

--
Jefferson Ogata : Internetworker, Antibozo

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

<Prev in Thread] Current Thread [Next in Thread>