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

[Masaki Kanno <kanno.masaki@xxxxxxxxxxxxxx>]

Mon, 12 May 2008 09:10:24 +0800, "Zhang, Jingke" wrote:

>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!

Hi Zhang,

Sounds good.  I will make a patch with your idea.

Best regards,
 Kan

>>> 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


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