[libvirt] [PATCH] Expose resource control capabilites on cache bank

[Daniel P. Berrange]

On Thu, Apr 06, 2017 at 06:29:47PM +0800, Eli Qiao wrote:
> 
> 
> On Thursday, 6 April 2017 at 6:10 PM, Daniel P. Berrange wrote:
> 
> > On Thu, Apr 06, 2017 at 12:05:54PM +0200, Martin Kletzander wrote:
> > > On Thu, Apr 06, 2017 at 10:51:44AM +0100, Daniel P. Berrange wrote:
> > > > On Thu, Apr 06, 2017 at 11:49:14AM +0200, Martin Kletzander wrote:
> > > > > On Thu, Apr 06, 2017 at 04:20:06PM +0800, Eli Qiao wrote:
> > > > > > This patch is based on Martin's cache branch.
> > > > > >  
> > > > > > This patch amends the cache bank capability as follow:
> > > > > >  
> > > > > > <bank id='0' level='3' type='unified' size='15360' unit='KiB' cpus='0-5'/>
> > > > > > <control min='768' unit='KiB' type='unified' nclos='4'/>
> > > > > > <bank id='1' level='3' type='unified' size='15360' unit='KiB' cpus='6-11'/>
> > > > > > <control min='768' unit='KiB' type='unified' nclos='4'/>
> > > > > >  
> > > > >  
> > > > >  
> > > >  
> > > >  
> > > > Either the XML is malformed, or the indentation is wrong. The indentation
> > > > suggests you want nested XML elements, but the parent element is an empty
> > > > tag, so you've actually got a flat namespace here.
> > > >  
> > > > >  
> > > > > Were we exposing the number of CLoS IDs before? Was there a discussion
> > > > > about it? Do we want to expose them? Probably yes, I'm just wondering.
> > > > >  
> > > >  
> > > >  
> > > > What are CLoS IDs and what are they used for ?
> > >  
> > > Effectively an ID for the allocation. The hardware has a limited number
> > > of them, in this case 4. I can't remember whether that number is
> > > per-bank, but it would not make much sense otherwise.
> > >  
> >  
> >  
> > So, if guests are requesting a private cache allocation, and cos id == 4,
> > then we can only run 4 guests ?
> >  
> >  
> 
> 
> I think yes, but it’s per bank resource (the bank here is equal to cache
> id), if you have 2 banks , you can create 8 guests (each has 1 bank
> allocation)

Ok, well if it is resource limiting in this way, then I think it is important
to expose in the capabilities. This information would be needed by openstack
schedular in order to avoid placing too guests on the same host when they have
requested cache allocation.

Picking a more obvious attr name would be nice though eg  'nallocations'

Regards,
Daniel
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