[Users] TSC clocksource gets lost after live migration

[Michal Skrivanek]

Hi,
this is more for the KVM folks I suppose…can you get the qemu process cmdline please?

Thanks,
michal

On 3 Apr 2014, at 12:13, Markus Stockhausen wrote:

> Hello,
> 
> we have an up to date ovirt 3.4 installation. Inside we are running SLES11 SP3
> VMs (Kernel 3.0.76-0.11). After live migration of these VMs they all of a sudden
> do not react any longer and CPU usage of the VM goes to 100%.
> 
> We identified kvm-clock source to be the culprit and therefore switched to another
> clocksource. We ended with hpet but are not happy with that as our inital goal
> was to use the more simple designed TSC clocksoure. 
> 
> The reason behind that is the question I have for you experts.
> 
> Our hosts all have the constant_tsc CPU flag available. Just to mention these
> are not identical hosts. We have a mix of Xeon 5500 and 5600 machines. E.G.
> [root at colovn01 ~]# cat /proc/cpuinfo | grep constant_tsc | wc -l
> 8
> 
> When we start the VM the client sees TSC as available clocksource:
> 
> colvm53:~ # cat /sys/devices/system/clocksource/clocksource0/available_clocksource
> kvm-clock tsc hpet acpi_pm
> 
> After the first live migration to another host that also has constant_tsc (see above)
> that flag is lost inside the VM.
> 
> colvm53:~ # cat /sys/devices/system/clocksource/clocksource0/available_clocksource
> kvm-clock hpet acpi_pm
> 
> Any ideas?
> 
> Markus
> 
> 
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