Re: [Xen-devel] RFC: vNUMA project

[George Dunlap <George.Dunlap@xxxxxxxxxxxxx>]

On Tue, Nov 11, 2014 at 5:36 PM, Wei Liu <wei.liu2@xxxxxxxxxx> wrote:
> Third stage:
>
>            Basic     PoD   Ballooning  Mem_relocation
> PV/PVH       Y       na       Y         na
> HVM          Y       Y        Y         X
>
> NUMA-aware PoD?

Hmm, that will certainly be interesting. :-)

The point of PoD is to allocate a chunk of memory at guest creation
time and have the VM balloon down to fit that amount of memory.

If we assume that vnodes correspond to some set of pnodes, then the
initial allocation will (ideally) have to come from *some* subset of
those pnodes; but depending on the situation, it may be any
combinaton.  So for example, a guest with 2 vnodes each with 2GiB each
might end up with 1G on each pnode, or 2 G on one pnode and none on
another.

In this case, the only way to get an ideal memory layout is to
communicate back to the balloon driver how much memory to free on each
virtual node.  If the split is 1G / 1G, then the balloon driver will
need to allocate 1G for each vnode.  If the split was 0.5G / 1.5G,
then it would have to allocate 1.5G / 0.5G, &c.

 -George

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