RE: [Xen-devel] [PATCH] Fix xmexamples about cpus

["Ian Pratt" <Ian.Pratt@xxxxxxxxxxxxx>]

> >Hi Kanno,
> >    We have tried cpus="^1" in the past. For we want to drop only
CPU1
> >no matter how many CPUs are on the machine. The result shows: CPU1
can
> >still be used by HVM and all the VCPU's affinity are "any cpu".
> >    So, do you think this setting is available? Or do we need some
> more
> >comments on this? Thanks!
> 
> Hi Zhang,
> 
> I think that a purpose to set "cpus" is to confine CPUs which VCPUs
run
> to a CPU or some CPUs.  If there are many CPUs on a machine, I think
> that we should avoid the setting for performance.

The "^1" syntax is quite useful if you're trying to reserve a CPU for
use by another domain e.g. domain0, but don't want to otherwise restrict
the guest.

We need to be able to deal with setting the affinity mask for a domain
(that is replicated to all VCPUs) as for individual VCPUs. I assume your
patch doesn't change the behaviour of the former?

BTW, it would also be nice to be able to specify CPUs by
node.socket.core.thread as opposed to just enumerated CPU number. It
should be possible to omit unused levels of the hierarchy, e.g. "0.3"
could be used to refer to the 4th core of the first socket on a dual
socket quad core machine.

If you're looking for further improvements in this area, enable CPU
groups to be defined and then allow domains/VCPUs to be assigned to a
group.


Thanks,
Ian 


> 
> Best regards,
>  Kan
> 
> 
> 
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