[Kimchi-devel] RFC: smt support

[Paulo Ricardo Paz Vital]

> 
> On 07/01/2014 11:32 PM, Aline Manera wrote:
> >
> > On 06/26/2014 07:27 PM, Christy Perez wrote:
> >> Quick poll for adding support for
> >> <cpu>
> >>      <topology sockets='1' cores='2' threads='1'/>
> >> </cpu>
> >>
> >> I know it would be nice to let users add it on a per-vm basis, but maybe
> >> it might be something that we'd rather just leave in the template only.
> >> Having it in the template only seems simpler when thinking about UI
> >> design, imo, but I'd love to hear what everyone else thinks.
> >
> > According to the reference 
> > https://www.ibm.com/developerworks/community/blogs/fe313521-2e95-46f2-817d-44a4f27eba32/entry/enabling_smt_on_powerkvm_guests?lang=en
> >
> > There are some restrictions to configure SMT what can not be intuitive 
> > for a Kimchi user.
> >
> > So I like the idea to keep it only on templates (at least for while) 
> > and see how Kimchi users react on that.
> > We will need to properly add a logic to get the best pairs of 
> > cores/threads according to the vcpus number.
> >
> > In my mind, we should only add a check box on Template edit: "Enable 
> > SMT" if checked Kimchi knows what it needs to do when creating a VM
> >

I think we can do something better! In addition to the check box, we can
provide a combo box with the available choices for SMT. These values are
static defined as SMT=1, SMT=2, SMT=4, or SMT=8. 

So, when the user select the SMT check box, the combo box make enable to
user select one of these 4 options. Then, at the moment to write the
XML, Kimchi backend do math to create the topology entry based on the
SMT value and the number of processors defined.

For example, if user sets a template to have 8 processors and SMT=4, the
backend must create following entry on the XML file:

<vcpu>8</vcpu>
<cpu>
<topology sockets='1' cores='2' threads='4'/>
</cpu>  
 
That's my 3 cents.
Thanks and best regards,
Paulo Vital