Xen devel - Apr 2010 - PV kernel boot parameter maxcpus has no effect?

Hi all,

I have a two-socket (each socket processor has 4 cores) machine, but only want
to use one socket processor. I give pv dom0 boot parameter maxcpus=4, but in
fact there is no effect, other cpus 4-7 are still used. Is this a bug or
something?

Shawn


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On Wed, Apr 28, 2010 at 11:07:36AM +0800, Yuyang Du
wrote:
> Hi all,
> 
> I have a two-socket (each socket processor has 4 cores) machine, but only
want to use one socket processor. I give pv dom0 boot parameter maxcpus=4, but
in fact there is no effect, other cpus 4-7 are still used. Is this a bug or
something?
> 
You need to give _Xen_ (xen.gz) option dom0_max_vcpus=X

-- Pasi


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>>> Pasi Kärkkäinen 04/28/10 8:33 AM >>>
>On Wed, Apr 28, 2010 at 11:07:36AM +0800, Yuyang Du wrote:
>> Hi all,
>> 
>> I have a two-socket (each socket processor has 4 cores) machine, but
only want to use one socket processor. I give pv
dom0 boot parameter maxcpus=4, but in fact there is no effect, other cpus 4-7
are still used. Is this a bug or
something?
>> 
>
>You need to give _Xen_ (xen.gz) option dom0_max_vcpus=X
Yes and no - the other scenario also has its use case (i.e. have Dom0 initially
just bring up a subset of the vCPU-s it
has been given).

However, given that the bringing up of secondary CPUs happens from common (even
arch-independent) code, the whole issue
seems a little suspicious - namely what indication he uses to see that there are
more than 4 vCPU-s in use by Dom0.

Jan


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