[Xen-users] Cron/Time is going crazy during load

[Fabian Zimmermann <xen-users@xxxxxxxxxxxxxxxxx>]

Hi,

first some infos about my system:

Debian Lenny (Xen 3.3.1 / 2.6.26-2-xen-amd64 )
running ~8 PV-DomUs (Debian Etch / 2.6.18.8-xen [i686] )

DomU-sysctl.conf:
xen.independent_wallclock=1

DomU:
cat /sys/devices/system/clocksource/clocksource0/available_clocksource
jiffies tsc pit
cat /sys/devices/system/clocksource/clocksource0/current_clocksource
jiffies

All DomUs are 100% equal, they execute some cronjobs every X minutes. 
The following problem is not limited to only one cronjob. It looks like 
the time is going crazy under load.
This job should be executed every 2 minutes:

...
Jun  9 23:54:01 host /USR/SBIN/CRON[13042]: (root) CMD (nice -n 15 
-command-)
Jun  9 23:56:01 host /USR/SBIN/CRON[13219]: (root) CMD (nice -n 15 
-command-)
Jun  9 23:58:01 host /USR/SBIN/CRON[13380]: (root) CMD (nice -n 15 
-command-)
...
Jun 10 03:11:03 host /USR/SBIN/CRON[32711]: (root) CMD (nice -n 15 
-command-)
Jun 10 03:11:10 host /USR/SBIN/CRON[403]: (root) CMD (nice -n 15 -command-)
Jun 10 03:11:14 host /USR/SBIN/CRON[541]: (root) CMD (nice -n 15 -command-)
Jun 10 03:11:17 host /USR/SBIN/CRON[594]: (root) CMD (nice -n 15 -command-)
Jun 10 03:11:18 host /USR/SBIN/CRON[631]: (root) CMD (nice -n 15 -command-)
Jun 10 03:11:18 host /USR/SBIN/CRON[699]: (root) CMD (nice -n 15 -command-)
Jun 10 03:11:19 host /USR/SBIN/CRON[746]: (root) CMD (nice -n 15 -command-)
Jun 10 03:11:20 host /USR/SBIN/CRON[1450]: (root) CMD (nice -n 15 -command-)
Jun 10 03:11:20 host /USR/SBIN/CRON[6659]: (root) CMD (nice -n 15 -command-)
Jun 10 03:11:20 host /USR/SBIN/CRON[1518]: (root) CMD (nice -n 15 -command-)
Jun 10 03:11:21 host /USR/SBIN/CRON[1686]: (root) CMD (nice -n 15 -command-)
Jun 10 03:11:24 host /USR/SBIN/CRON[1881]: (root) CMD (nice -n 15 -command-)
Jun 10 03:11:24 host /USR/SBIN/CRON[1887]: (root) CMD (nice -n 15 -command-)
Jun 10 03:11:24 host /USR/SBIN/CRON[1989]: (root) CMD (nice -n 15 -command-)
Jun 10 03:11:25 host /USR/SBIN/CRON[2170]: (root) CMD (nice -n 15 -command-)
Jun 10 03:11:29 host /USR/SBIN/CRON[2366]: (root) CMD (nice -n 15 -command-)
Jun 10 03:11:30 host /USR/SBIN/CRON[2584]: (root) CMD (nice -n 15 -command-)
Jun 10 03:11:31 host /USR/SBIN/CRON[2941]: (root) CMD (nice -n 15 -command-)
Jun 10 03:11:32 host /USR/SBIN/CRON[3336]: (root) CMD (nice -n 15 -command-)
Jun 10 03:11:33 host /USR/SBIN/CRON[3506]: (root) CMD (nice -n 15 -command-)
Jun 10 03:11:33 host /USR/SBIN/CRON[3665]: (root) CMD (nice -n 15 -command-)
Jun 10 03:11:33 host /USR/SBIN/CRON[3884]: (root) CMD (nice -n 15 -command-)
Jun 10 03:11:34 host /USR/SBIN/CRON[4108]: (root) CMD (nice -n 15 -command-)
Jun 10 03:11:34 host /USR/SBIN/CRON[4323]: (root) CMD (nice -n 15 -command-)
Jun 10 03:11:34 host /USR/SBIN/CRON[4367]: (root) CMD (nice -n 15 -command-)
Jun 10 03:11:35 host /USR/SBIN/CRON[4700]: (root) CMD (nice -n 15 -command-)
Jun 10 03:11:45 host /USR/SBIN/CRON[316]: (root) CMD (nice -n 15 -command-)
Jun 10 03:12:12 host /USR/SBIN/CRON[929]: (root) CMD (nice -n 15 -command-)
Jun 10 03:12:37 host /USR/SBIN/CRON[7162]: (root) CMD (nice -n 15 -command-)
Jun 10 03:13:09 host /USR/SBIN/CRON[10560]: (root) CMD (nice -n 15 
-command-)
Jun 10 03:13:11 host /USR/SBIN/CRON[7368]: (root) CMD (nice -n 15 -command-)
Jun 10 03:14:05 host /USR/SBIN/CRON[12202]: (root) CMD (nice -n 15 
-command-)
Jun 10 03:16:06 host /USR/SBIN/CRON[15341]: (root) CMD (nice -n 15 
-command-)
Jun 10 03:18:03 host /USR/SBIN/CRON[17821]: (root) CMD (nice -n 15 
-command-)
Jun 10 03:20:01 host /USR/SBIN/CRON[20941]: (root) CMD (nice -n 15 
-command-)
Jun 10 03:22:01 host /USR/SBIN/CRON[24310]: (root) CMD (nice -n 15 
-command-)
This is killing my DomUs, because they kill themself with OOM. I will 
now try to disable independent_wallclock and disable the DomU-ntp.
What else could I do/check?

Why do I don't have a "xen" clocksource?

Thanks,
Fabian

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