[Kimchi-devel] [RFC] Guest/Template CPU setup with topology

[Aline Manera]

Hi Daniel,

On 11/08/2016 05:14 PM, Daniel Henrique Barboza wrote:
> Hi there,
>
> At this moment Kimchi support for guest and template CPU setup is
> underwhelming. Here's what I've found that needs improving:
>
> - edit template:
>
> * calculation of max CPUs is wrong when considering a topology. Max CPU
> is the value of sockets * cores *  threads. At this moment it is 
> considering only
> cores * threads, defaulting sockets to 1.
>

It is working as designed. When we started discussing about that, we 
agreed to ask minimal information from user and after some 
investigation, we decided the sockets value would be set as 1.

The most important value IMO is the number of threads (X) that 
corresponds to the SMT X value and can not be freely inputed as it 
depends on CPU support.

If you are proposing to add sockets there too, I am OK with that. Just 
want to understand the limitations we are adding while assuming sockets 
=  1.

> * There is no way to set or even see the value of sockets. Given that 
> this value
> is used in the calculation of the max CPUs, it should be at least 
> visible and, in my
> opinion, editable
>

Same I commented above.

>
> - edit guest (not running):
> * If the guest was created with a CPU topology, there is no way to 
> edit it. The only
> way to edit a topology at this moment is on the template level.
>

And it is also impacting user to update max vcpus and vcpus value. =/

>
> My proposal is:
>
> edit template:
> - fix the max CPU calculation to consider the sockets.
> - add a field to allow the 'sockets' to be set at will. Default value 
> will be retrieved
> by the kimchi/host/cpuinfo API as a reference (same think as with 
> cores and threads
> today).
>

OK for me. Just want to understand the limitations we are adding while 
assuming sockets =  1.

> edit guest:
> - if the guest was created with a CPU topology, allow the topology to 
> be edited when
> the guest is turned OFF.
>

ACK.

>
> Thoughts?
>
>
>
> ps: this RFC is also related to the feedback of "Bug fix #1072 - 
> changing vpus
> verification​".
>
>
> Daniel
>
>
>
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