[Xen-devel] RE: Host Numa informtion in dom0

[Ian Pratt <Ian.Pratt@xxxxxxxxxxxxx>]

> > If guest NUMA is disabled, we just use a single node mask which is the
> > union of the per-VCPU node masks.
> >
> > Where allowed node masks span more than one physical node, we should
> > allocate memory to the guest's virtual node by pseudo randomly striping
> > memory allocations (in 2MB chunks) from across the specified physical
> > nodes. [pseudo random is probably better than round robin]
> 
> Do we really want to support this? I don't think the allowed node masks
> should span more than one physical NUMA node. We also need to look at I/O
> devices as well.

Given that we definitely need this striping code in the case where the guest is 
non NUMA, I'd be inclined to still allow it to be used even if the guest has 
multiple NUMA nodes. It could come in handy where there is a hierarchy between 
physical NUMA nodes, enabling for example striping to be used between a pair of 
'close' nodes, while exposing the higher-level topology of sets of the paired 
nodes to be exposed to the guest. 

Ian



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