[Kimchi-devel] RFC: smt support

[Aline Manera]

On 07/02/2014 11:30 AM, Christy Perez wrote:
>
>
>
> On Wed, 2014-07-02 at 09:50 -0300, Paulo Ricardo Paz Vital wrote:
>>>
>>> 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'm fine with only on template edit. In the future, though, hopefully
> we'll be adding maybe an "Advanced" sub-panel when creating templates
> that lets users do things like this?
>>

Agree.
This kind of info may be too complex for a Kimchi user
I'd say to start only with the check box and in future (after getting 
feedbacks) add more details in the "Advanced" panel

>> 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:
>>
> What if they set 7 processors? We could disable the SMT checkboxes if
> their CPU # wasn't a multiple of anything. So we'll probably have to
> come up with very good help/hint text for this.
>
> Or, if they select SMT, the CPU box becomes un-editable, and then
> selecting one of the SMT options, the CPU count (in the un-editable
> field) is updated so that they can understand what VCPU count they'll
> end up before they click OK.
>
>> <vcpu>8</vcpu>
>> <cpu>
>> <topology sockets='1' cores='2' threads='4'/>
>> </cpu>
>>
>> That's my 3 cents.
>> Thanks and best regards,
>> Paulo Vital
>>
>
>