[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: [Xen-devel] RFC: Still TODO for 4.2? xl domain numa memory allocation vs xm/xend

On Fri, Jan 20, 2012 at 07:59:28AM +0000, Ian Campbell wrote:
> On Thu, 2012-01-19 at 21:14 +0000, Pasi Kärkkäinen wrote:
> > On Wed, Jan 04, 2012 at 04:29:22PM +0000, Ian Campbell wrote:
> > > 
> > > Has anybody got anything else? I'm sure I've missed stuff. Are there any
> > > must haves e.g. in the paging/sharing spaces?
> > > 
> > 
> > Something that I just remembered:
> > http://wiki.xen.org/xenwiki/Xen4.1
> > 
> > "NUMA-aware memory allocation for VMs. xl in Xen 4.1 will allocate
> > equal amount of memory from every NUMA node for the VM. xm/xend
> > allocates all the memory from the same NUMA node."
> I'm not that familiar with the NUMA support but my understanding was
> that memory was allocated by libxc/the-hypervisor and not by the
> toolstack and that the default was to allocate from the same numa nodes
> as domains the processor's were pinned to i.e. if you pin the processors
> appropriately the Right Thing just happens. Do you believe this is not
> the case and/or not working right with xl?
> CCing Juergen since he added the cpupool support and in particular the
> cpupool-numa-split option so I'm hoping he knows something about NUMA
> more generally.
> > Is this something that should be looked at?
> Probably, but is anyone doing so?
> > Should the numa memory allocation be an option so it can be controlled
> > per domain? 
> What options did xm provide in this regard?
> Does xl's cpupool (with the cpupool-numa-split option) server the same
> purpose?
> > The default libxl behaviour might cause unexpected performance issues
> > on multi-socket systems? 
> I'm not convinced libxl is behaving any different to xend but perhaps
> someone can show me the error of my ways.

See this thread: 

where Stefano wrote:
"I think we forgot about this feature but it is important and hopefully
somebody will write a patch for it before 4.2 is out."

-- Pasi

Xen-devel mailing list



Lists.xenproject.org is hosted with RackSpace, monitoring our
servers 24x7x365 and backed by RackSpace's Fanatical Support®.