[pve-devel] [PATCH] memory hotplug patch v6

Dietmar Maurer dietmar at proxmox.com
Wed Jan 21 08:19:40 CET 2015

> I never have think at something like that.
> It seem to solve all the problems :)
> (just one little note: we need to keep some "static" memory (qemu -m X), for
> vm start,
>  because dimm modules are not readeable until initramfs is loaded).

Sigh, that is a problem, because each OS needs a different setting for startup
Using 2 different configuration would solve that:

memory: XXX # assigned at startup
dimm_memory: XXX # hot plugable memory

> > I think it could work, but currently unplug is not implemented in qemu, 
> >>We do not need unplug with above fixed dimm mappings.
> I don't understand this. Why don't we need unplug ?
> If we reduce the memory, we want to unplug dimm modules right ?

Sure. But we do not need 'unplug' when we 'add' memory (as suggested by daniel).
> > and also it's possible for advanced users to specify topology manually 
> > qm set vmid -dimmX size,numa=node 
> >
> >>Why is that required? Isn't it possible to assign that automatically
> >>(distribute 
> >>among all 
> >>numa nodes)?
> I think we can simply hotplug the dimm on the node with less memory.
> We just need to care about live migration, and assign same memory modules on
> same numa node.

BTW, are there systems with odd number of NUMA nodes?

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