Messages in this thread | | | From | Ferenc Wagner <> | Subject | Re: doubled idle count | Date | Fri, 07 Nov 2008 16:20:47 +0100 |
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Jeremy Fitzhardinge <jeremy@goop.org> writes:
> Ferenc Wagner wrote: > >> After upgrading a Xen virtual machine to Debian's 2.6.26-4 kernel, I >> noticed that the idle counter doubled its pace on one of the machines: >> [command line stuff elided, graph follows] > > So you're saying that they are identical Xen and guest kernel binaries, > but one of three is showing doubled idle time?
I've affirmed this in detail on Sept 19. Now I'm trying to resurrect this thread, maybe some visual stimulation will help...
[unhandled content-type:image/png] Consider the above CPU graph (courtesy of Munin, tweaked to accept values above 100%). This virtual machine (Linux 2.6.26.6 + migration patches from 2.6.27) can run on two identically configured hosts running the 3.2.1 hypervisor and a Linux 2.6.18 dom0 kernel.
Nov 2 15:22 (rising edge): domU shut down and recreated with clocksource=jiffies.
Nov 3 16:01 (nothing to see): domU shut down again and recreated without specifying clocksource on the kernel command line. It selected the xen clocksource.
Nov 6 17:22 (falling edge): domU live migrated to the other host.
So live migration alone shaked the idle figures back in shape.
I really wonder if anybody has some insight into this anomaly. In itself it isn't a problem, but I've got other issues (some timing related, like serial overruns, and also some dom0 crashes), so I'd like to get rid of anything suspicious.
Regards, Feri.
xm info on the two dom0-s:
host : xen2-ha release : 2.6.18-6-xen-686 version : #1 SMP Mon Oct 13 20:36:55 UTC 2008 machine : i686 nr_cpus : 4 nr_nodes : 1 cores_per_socket : 1 threads_per_core : 2 cpu_mhz : 3056 hw_caps : bfebfbff:00000000:00000000:00000080:00004400 total_memory : 3071 free_memory : 2781 node_to_cpu : node0:0-3 xen_major : 3 xen_minor : 2 xen_extra : -1 xen_caps : xen-3.0-x86_32p xen_scheduler : credit xen_pagesize : 4096 platform_params : virt_start=0xf5800000 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 15:25:00 UTC 2008 xend_config_format : 4
domU config:
name = "noc.grid" kernel = "/home/wferi/vmlinuz-2.6.26-1-686-bigmem" ramdisk = "/home/wferi/initrd.img-2.6.26-1-686-bigmem" memory = 512 vif = [ 'mac=00:16:3e:00:00:13, bridge=br894', 'mac=00:16:3e:00:00:30, bridge=br897' ] root = "/dev/mapper/noc-root ro" extra = "" on_poweroff = 'destroy' on_reboot = 'restart' on_crash = 'restart'
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