Re: [PATCH 3/3] numa: Initialize node initiator with respect to .has_cpu

[Michal Privoznik]

On 6/2/20 10:00 AM, Tao Xu wrote:
> On 6/1/2020 4:10 PM, Michal Privoznik wrote:
> > On 5/29/20 5:09 PM, Igor Mammedov wrote:
> > > On Fri, 29 May 2020 15:33:48 +0200
> > > Michal Privoznik <mprivozn@redhat.com> wrote:
> > >
> > > > The initiator attribute of a NUMA node is documented as the 'NUMA
> > > > node that has best performance to given NUMA node'. If a NUMA
> > > > node has at least one CPU there can hardly be a different node
> > > > with better performace and thus all NUMA nodes which have a CPU
> > > > are initiators to themselves. Reflect this fact when initializing
> > > > the attribute.
> > >
> > > It is not true in case of the node is memory-less
> >
> > Are you saying that if there's a memory-less NUMA node, then it needs to
> > have initiator set too? Asking mostly out of curiosity because we don't
> > allow memory-less NUMA nodes in Libvirt just yet. Nor cpu-less, but my
> > patches that I'm referring to in cover letter will allow at least
> > cpu-less nodes. Should I allow both?
> QEMU now is not support memory-less NUMA node, but in hardware may be 
> supported. So we reserve this type of NUMA node for future usage. And 
> QEMU now can support cpu-less NUMA node, for emulating some "slow" 
> memory(like some NVDIMM).

Oh yeah, I understand that. But it doesn't explain why initiator needs 
to be specified for NUMA nodes with cpus and memory, or does it? Maybe 
I'm still misunderstanding what the initiator is.

> > Also, can you shed more light into why machine_set_cpu_numa_node() did
> > not override the .initiator?

And this one is still unanswered too. Because from user's perspective, 
initiator has to be set on all NUMA nodes (if HMAT is enabled) and it 
seems like this auto assignment code is not run/not working.

Michal