Hello, On a xenserver with several (39) domUs, we experience problems with the system clock of the domUs. The clock seems to drift away several seconds up to two minutes from the dom0 clock. We do have set independent_wallclock=0. According to the docs (i.e. http://wiki.xensource.com/xenwiki/InstallationNotes) that way domUs should use the dom0 clock, but apparently that''s not the case. permitted_clock_jitter is set to 10000000. did we miss anything, or is it still required to run an ntpd on the dom0? and if this is the case, where do we find documentation about howto setup both dom0 and domUs to use this ntpd for the system clock? The dom0 runs the debian 2.6.26-1-xen-amd64 kernel with 3.2 xen utils: # dpkg -l | grep xen ii libxenstore3.0 3.2.1-2 Xenstore communications library for Xen ii linux-image-2.6.26-1-xen-amd64 2.6.26-12 Linux 2.6.26 image on AMD64, oldstyle Xen support ii linux-modules-2.6.26-1-xen-amd64 2.6.26-12 Linux 2.6.26 modules on AMD64 ii xen-hypervisor-3.2-1-amd64 3.2.1-2 The Xen Hypervisor on AMD64 ii xen-utils-3.2-1 3.2.1-2 XEN administrative tools ii xen-utils-common 3.2.0-2 XEN administrative tools - common files ii xenstore-utils 3.2.1-2 Xenstore utilities for Xen # xm info host : xen0 release : 2.6.26-1-xen-amd64 version : #1 SMP Mon Dec 15 20:07:26 UTC 2008 machine : x86_64 nr_cpus : 4 nr_nodes : 1 cores_per_socket : 2 threads_per_core : 1 cpu_mhz : 1995 hw_caps : 178bf3ff:ebd3fbff:00000000:00000010:00002001:00000000:0000001f total_memory : 32767 free_memory : 3120 node_to_cpu : node0:0-3 xen_major : 3 xen_minor : 2 xen_extra : -1 xen_caps : xen-3.0-x86_64 xen-3.0-x86_32p hvm-3.0-x86_32 hvm-3.0-x86_32p hvm-3.0-x86_64 xen_scheduler : credit xen_pagesize : 4096 platform_params : virt_start=0xffff800000000000 xen_changeset : unavailable cc_compiler : gcc version 4.3.1 (Debian 4.3.1-2) cc_compile_by : waldi cc_compile_domain : debian.org cc_compile_date : Sat Jun 28 09:32:18 UTC 2008 xend_config_format : 4 greetings, jonas _______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users
On Sun, 11 Jan 2009, Jonas Meurer wrote:> Hello, > > On a xenserver with several (39) domUs, we experience problems with the > system clock of the domUs. The clock seems to drift away several seconds > up to two minutes from the dom0 clock. > > We do have set independent_wallclock=0. According to the docs (i.e. > http://wiki.xensource.com/xenwiki/InstallationNotes) that way domUs > should use the dom0 clock, but apparently that''s not the case.We run our own video applications on xen, so a drift on less then a second is a big deal to us. It''s a hack, but the only way we have been able to get stable time is to set wallclock=1 and then run chrony on them. http://chrony.sunsite.dk/ We still have drift, but it now is only -.02 - .03 ms over 1 sec.><>Nathan Stratton CTO, BlinkMind, Inc. nathan at robotics.net nathan at blinkmind.com http://www.robotics.net http://www.blinkmind.com _______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users
I was able to get rid of much of the drift by reducing the kernel freqency to 100 Hz In centos5 you can use the kernel option divider=10 In other distros you either can''t do it without recompiling or there is a different kernel switch. -- Randy www.FastServ.com ---------- Original Message ----------- From: Nathan Stratton <nathan@robotics.net> To: Jonas Meurer <jonas@freesources.org> Cc: xen-users <xen-users@lists.xensource.com> Sent: Sun, 11 Jan 2009 12:54:13 -0600 (CST) Subject: Re: [Xen-users] drifting clock in domUs> On Sun, 11 Jan 2009, Jonas Meurer wrote: > > > Hello, > > > > On a xenserver with several (39) domUs, we experience problems with the > > system clock of the domUs. The clock seems to drift away several seconds > > up to two minutes from the dom0 clock. > > > > We do have set independent_wallclock=0. According to the docs (i.e. > > http://wiki.xensource.com/xenwiki/InstallationNotes) that way domUs > > should use the dom0 clock, but apparently that''s not the case. > > We run our own video applications on xen, so a drift on less then a > second is a big deal to us. It''s a hack, but the only way we have > been able to get stable time is to set wallclock=1 and then run > chrony on them. http://chrony.sunsite.dk/ > > We still have drift, but it now is only -.02 - .03 ms over 1 sec. > > ><> > Nathan Stratton CTO, BlinkMind, Inc. > nathan at robotics.net nathan at > blinkmind.com http://www.robotics.nethttp://www.blinkmind.com> > _______________________________________________ > Xen-users mailing list > Xen-users@lists.xensource.com > http://lists.xensource.com/xen-users------- End of Original Message ------- _______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users