27 нояб. 2015 г. 14:15 пользователь "Martin Kletzander" <mkletzan@redhat.com> написал:

On Fri, Nov 20, 2015 at 04:31:56PM +0100, Piotr Rybicki wrote:

...

Hi.

I would like to workaround a bug, when after live-migration of KVM guest, there is a 100% steal time shown in guest.

I've read, that disabling 'kvm_steal_time' feature should workarund this bug, but i can't find a way to disable it in libvirt's domain xml file.

There is no support for that in libvirt. Either we must addit ad a feature (patches welcome), but if that's there just for a workaround, I would suggest chasing the original bug.

If you just want to check that the workaround works, you could check how the '-cpu ' parameter looks like when the domain is running and then use the unsupported way of adding parameters to the qemu commandline to specify the -cpu parameter again (qemu should use the last one, so it should work), something like this:

<domain type='kvm' xmlns:qemu='http://libvirt.org/schemas/domain/qemu/1.0

'>

... <qemu:commandline> <qemu:arg value='-cpu'/> <qemu:arg value='${CPU_SPEC},-kvm_steal_time'/> </qemu:commandline> </domain>

where ${CPU_SPEC} is the next parameter after the '-cpu' one from the command line, so for qemu command line similar to this:

qemu-kvm ... -cpu Nehalem,+feat,something ...

the line in XML would be:

<qemu:arg value='Nehalem,+feat,something,-kvm_steal_time'/>

HTH,

Martin

...

Tried in <cpu> section: <feature policy='disable' name='kvm_steal_time'/> but that doesn't work.

Also, couldn't find any related information in libvirt documentation. Google helps neither.

How can I disable this feature?

Thanks in advance. Piotr Rybicki

Does it possible to calculate steal time for vm if I have libvirt and domain stats? _______________________________________________

...

libvirt-users mailing list libvirt-users@redhat.com https://www.redhat.com/mailman/listinfo/libvirt-users

_______________________________________________ libvirt-users mailing list libvirt-users@redhat.com https://www.redhat.com/mailman/listinfo/libvirt-users

2015-11-27 16:57 GMT+03:00 Martin Kletzander <mkletzan@redhat.com>:

I don't think we report that in domain stats, but top/virt-top could help with that.

Ok libvirt can't get this value, but does it possible if i know cpu stats of domain and host info (i don't know which =)) determine for specific domain does it possible have steal time or not? -- Vasiliy Tolstov, e-mail: v.tolstov@selfip.ru

...

I've read, that disabling 'kvm_steal_time' feature should workarund this bug, but i can't find a way to disable it in libvirt's domain

xmlfile.

There is no support for that in libvirt. Either we must addit ad a feature (patches welcome), but if that's there just for a workaround, I would suggest chasing the original bug.

If you just want to check that the workaround works, you could check how the '-cpu ' parameter looks like when the domain is running and then use the unsupported way of adding parameters to the qemu commandline to specify the -cpu parameter again (qemu should use the last one, so it should work), something like this:

<domain type='kvm' xmlns:qemu='http://libvirt.org/schemas/domain>/qemu/1.0'> ... <qemu:commandline> <qemu:arg value='-cpu'/> <qemu:arg value='${CPU_SPEC},-kvm_steal_time'/> </qemu:commandline> </domain>

where ${CPU_SPEC} is the next parameter after the '-cpu' one from the command line, so for qemu command line similar to this:

qemu-kvm ... -cpu Nehalem,+feat,something ...

the line in XML would be:

<qemu:arg value='Nehalem,+feat,something,-kvm_steal_time'/>

Thank You Martin, that helped. Just for information, commit for this bug in kernel: http://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=7c... Best regards Piotr Rybicki