Re: [Xen-devel] [PATCH v6 00/10] vnuma introduction

[Wei Liu <wei.liu2@xxxxxxxxxx>]

On Tue, Jul 22, 2014 at 05:06:37PM +0200, Dario Faggioli wrote:
[...]
> 
> > > With the following guest configuration, in terms of vcpu pinning:
> > > 
> > > 1) 2 vCPUs ==> same pCPUs
> > 
> > 4 vcpus, I think.
> > 
> > > root@benny:~# xl vcpu-list 
> > > Name                                ID  VCPU   CPU State   Time(s) CPU 
> > > Affinity
> > > debian.guest.osstest                 9     0    0   -b-       2.7  0
> > > debian.guest.osstest                 9     1    0   -b-       5.2  0
> > > debian.guest.osstest                 9     2    7   -b-       2.4  7
> > > debian.guest.osstest                 9     3    7   -b-       4.4  7
> > > 
> What I meant with "2 vCPUs" was that I was putting 2 vCPUs of the guest
> (0 and 1) on the same pCPU (0), and the other 2 (2 and 3) on another
> (7).
> 
> That should have meant a topology that does not share at least the least
> cache level in the guest, but it is not.
> 

I see.

> > > 2) no SMT
> > > root@benny:~# xl vcpu-list 
> > > Name                                ID  VCPU   CPU State   Time(s) CPU
[...]
> So, no, that is not giving the same result as in Dom0. :-(
> 
> > > This is not the case for dom0 where (I booted with dom0_max_vcpus=4 on
> > > the xen command line) I see this:
> > > 
> > 
> > I guess this is because you're basically picking pcpu 0-3 for Dom0. It
> > doesn't matter if you pin them or not.
> > 
> That makes total sense, and in fact, I was not surprised about Dom0
> looking like this... I rather am about not being able to get a similar
> topology for the guest, no matter how I pin it... :-/
> 

I guess it might also be related to the different CPUID policy Dom0 and
DomU have. Though in theory Dom0 and DomU are both PV domains they see
different CPUIDs, I think.

I only studied code to the point that I was able to manipulate topology
as I saw fit, so I could be wrong...

Wei

> Dario
> 
> -- 
> <<This happens because I choose it to happen!>> (Raistlin Majere)
> -----------------------------------------------------------------
> Dario Faggioli, Ph.D, http://about.me/dario.faggioli
> Senior Software Engineer, Citrix Systems R&D Ltd., Cambridge (UK)
> 



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