WARNING - OLD ARCHIVES

This is an archived copy of the Xen.org mailing list, which we have preserved to ensure that existing links to archives are not broken. The live archive, which contains the latest emails, can be found at http://lists.xen.org/
   
 
 
Xen 
 
Home Products Support Community News
 
   
 

xen-devel

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

Masaki Kanno wrote:
> Hi Ian,
> 
> Fri, 9 May 2008 13:07:31 +0100, "Ian Pratt" wrote:
> 
>>>> 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.
> 
> "cpus" is parsed from left side, and the "^1" negates the values which
> was already parsed.  So "0-3,^1,1" and "0-3" are equivalent.
> The parsing of "cpus" cannot handle "negation" from a beginning
> because there is not a value to negate.
> 
> But, I'm thinking that I want to implement Zhang's demand since I get
> your comment.  So I have idea as follows.
> 
>   cpus = "0:,^1"
> 
> The "0:" means "0 or later".  How about it?
> 

Hi Kanno,
    I think a "non-boundary" range may be needed to define the
expression. How about this:
    "x-", means from CPUx to the last CPU. For example, "0-" means 0 or
later.
    "-x", means from CPU0 to CPUx, for example, "-3" means "0,1,2,3". 
    Thank you!

> 
>> 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?
> 
> Could you look at the following changest?
> 
>  http://xenbits.xensource.com/xen-unstable.hg/rev/5c3df1bded82
> 
> 
>> 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.
> 
> I got interest for your suggestion.  Let me think for the time being.
> 
> 
> Best regards,
>  Kan



Thanks,
Zhang Jingke

_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxxxxxxxx
http://lists.xensource.com/xen-devel