libvirt users - May 2019 - Re: Running all my virtual machines with a low priority

>> I have an Ubuntu 18.04 system. What is the easiest way to run all of my
virtual machines with a low priority? Say a "nice" level of 15.
> 
> You can use the  <vcpusched>  (and related elements) to control
> the schedular nice level up or down
> 
>    https://libvirt.org/formatdomain.html#elementsCPUTuning
Thanks for your quick answer.

I took at look at that documentation, but I did not quite understand it. It
talks about vCPUs and how they are scheduled. My guess is that it is all
about how those virtual CPUs are scheduled against each other.

However, I wanted to lower the priority of all virtual machines against other
processes on the host system.

Regards,
   rdiez

On Wed, May 01, 2019 at 11:41:17AM +0200, R. Diez wrote:
> 
> > > I have an Ubuntu 18.04 system. What is the easiest way to run all
of my virtual machines with a low priority? Say a "nice" level of 15.
> > 
> > You can use the  <vcpusched>  (and related elements) to control
> > the schedular nice level up or down
> > 
> >    https://libvirt.org/formatdomain.html#elementsCPUTuning
> 
> Thanks for your quick answer.
> 
> I took at look at that documentation, but I did not quite understand it. It
> talks about vCPUs and how they are scheduled. My guess is that it is all
> about how those virtual CPUs are scheduled against each other.
> 
> However, I wanted to lower the priority of all virtual machines against
other processes on the host system.
You would have to set the priority of all vCPUs in each guest, as well
as emulator threads in each guest (the latter needs very new libvirt).

Regards,
Daniel
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> You would have to set the priority of all vCPUs in each guest, as well
> as emulator threads in each guest (the latter needs very new libvirt).
This does not seem a viable option then with Ubuntu 18.04. And changing XML on
all guest VMs is extra work.

Is there no other way? For example, are all such virtual machines not some
daemon or systemd unit or set of units? Would it be feasible to lower the
priority on all of those? Or is that not easy to do either?

Thanks again,
   rdiez