On 08.04.2022 13:16, Roger Pau Monné wrote: > On Fri, Apr 08, 2022 at 12:08:02PM +0100, Julien Grall wrote: >> 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.
I disagree: Unlike for DomU there's no way to keep a "reserve" of vCPU-s for Dom0, except by offlining some once Dom0 runs. Hence this "max" in the name is quite applicable. Jan
