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

[Julien Grall <julien@xxxxxxx>]

Hi Roger,

On 08/04/2022 12:16, Roger Pau Monné wrote:
> 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.
Unfortunately, Arm doesn't support the min-max nomenclature.

> But given Jans suggestion we might want to go for something more
> complex?
I think we already have some knowledge about each HW (i.e. grub vs 
uboot) in Osstest. So I think it would be fine to extend the knowledge 
and add the number of CPUs.
Cheers,

--
Julien Grall