Re: [xen-4.12-testing test] 169199: regressions - FAIL

[Roger Pau Monné <roger.pau@xxxxxxxxxx>]

On Fri, Apr 08, 2022 at 12:08:02PM +0100, Julien Grall wrote:
> Hi,
> 
> On 08/04/2022 12:01, Roger Pau Monné wrote:
> > > > I could add a suitable dom0_max_vcpus parameter to osstest.  XenServer
> > > > uses 16 for example.
> > > 
> > > I'm afraid a fixed number won't do, the more that iirc there are
> > > systems with just a few cores in the pool (and you don't want to
> > > over-commit by default).
> > 
> > But this won't over commit, it would just assign dom0 16 vCPUs at
> > most, if the system has less than 16 vCPUs that's what would be
> > assigned to dom0.
> 
> AFAICT, this is not the case on Arm. If you ask 16 vCPUs, then you will get
> that number even if there are 8 pCPUs.
> 
> In fact, the documentation of dom0_max_vcpus suggests that the numbers of
> vCPUs can be more than the number of pCPUs.

It was my understanding that you could only achieve that by using the
min-max nomenclature, so in order to force 16 vCPUs always you would
have to use:

dom0_max_vcpus=16-16

Otherwise the usage of '_max_' in the option name is pointless, and it
should instead be dom0_vcpus.

Anyway, I could use:

dom0_max_vcpus=1-16

Which is unambiguous and should get us 1 vCPU at least, or 16vCPUs at
most.

But given Jans suggestion we might want to go for something more
complex?

Thanks, Roger.