Re: [libvirt] [RFC PATCH 0/2] Introduce RDT memory bandwidth allocation support

On 2018年06月08日 21:00, Pavel Hrdina wrote: > On Wed, Jun 06, 2018 at 03:46:37PM +0800, bing.niu wrote: > > Hi Pavel, > > > > On 2018年06月06日 13:56, bing.niu wrote: > > > > > > > > > > Then there is the domain XML, for CAT we use this: > > > > > > > > <domain> > > > >    ... > > > >    <cputune> > > > >      ... > > > >      <cachetune vcpus='0-3'> > > > >        <cache id='0' level='3' type='both' size='3' unit='MiB'/> > > > >        <cache id='1' level='3' type='both' size='3' unit='MiB'/> > > > >      </cachetune> > > > >      ... > > > >    <cputune> > > > >    ... > > > > </domain> > > > > > > > > so the possible domain XML could look like this: > > > > > > > > <domain> > > > >    ... > > > >    <cputune> > > > >      ... > > > >      <memory vcpus='0-3'> > > > >        <socket id='0' bandwidth='30'/> > > > >        <socket id='1' bandwidth='20'/> > > > >      </memory> > > > >      ... > > > >    <cputune> > > > >    ... > > > > </domain> > > > > > > > > Again, the element names 'memory' and 'socket' can be named differently. > > > socket --> node? > > > > > > Since the existing virrestrl implementation only care about cache part > > > during development, So we may need change some names of structure and > > > functions when enable MBA. How do you think > > > > > > > > Pavel > > > > > > > > > Is that possible to support MBA by extending CAT in domain XML? Since each > > <cachetune> will map to one virresctrlalloc structure and create a rdt_group > > in resctrl fs. Each rdt_group will have it's own closid. this work perfect > > if CAT only available. However, if MBA coming in with CAT enabled also, ike > > this. > > > > <domain> > > ... > > <cputune> > > ... > > <cachetune vcpus='0-3'> > > <cache id='0' level='3' type='both' size='3' unit='MiB'/> > > <cache id='1' level='3' type='both' size='3' unit='MiB'/> > > </cachetune> > > <memory vcpus='2-3'> > > <socket id='0' bandwidth='30'/> > > <socket id='1' bandwidth='20'/> > > </memory> > > ... > > <cputune> > > ... > > </domain> > > > > we have to make sure those two allocating will not have vcpu overlapped. > > like this, > > > > if (virBitmapOverlaps(def->cachetunes[i]->vcpus, vcpus) > > || virBitmapOverlaps(def->memroy->vcpus, vcpus)) { > > virReportError(VIR_ERR_XML_ERROR, "%s", > > _("Overlapping vcpus in cachetunes")); > > goto cleanup; > > that looks like introducing some dependency between CAT and MBA. > > Is that possible we rename cachetune so that handle CAT MBA together one > > section? > > I would like to avoid mixing cache tune and memory bandwidth under > 'cachetune' element. But this is a good point, we need to make sure > that the 'vcpus' is not overlapping. > > Renaming existing XML element is not possible, it needs to be backward > compatible. > > Pavel thanks for clarification ；）. we will do a cross check about cachetune and memory to make sure no vcpus overlapping. I just feel this may confuse people. Since we must tell them vcpus cannot overlapping for cachetune and memory, but vcpus can be equal. this should be the most common case--- create one rdt group for one vm.