Re: [Xen-devel] RFC: automatic NUMA placement

[Juergen Gross <juergen.gross@xxxxxxxxxxxxxx>]

On 09/16/10 17:52, Dan Magenheimer wrote:
> I am in favor of this being optional rather than default.
> It is another case of the tradeoff between performance
> and flexibility that I have ranted about several times
> on xen-devel, and Xen's policy seems to be fairly random
> (sometimes Xen chooses performance over flexibility and
> sometimes the opposite).
>
> I went looking through xen-devel archives for a previous
> discussion on this (and to find when the code got added)
> but couldn't find it... if you have links to the patch
> and discussion, please post.
Took a while to find it, but hg log helped :-)

Patch: 
http://xenbits.xensource.com/staging/xen-unstable.hg?diff/b58180cf8ab8/tools/python/xen/xend/XendDomainInfo.py
Discussion: 
http://lists.xensource.com/archives/html/xen-devel/2008-02/msg00883.html
> > -----Original Message-----
> > From: Juergen Gross [mailto:juergen.gross@xxxxxxxxxxxxxx]
> > Sent: Thursday, September 16, 2010 7:39 AM
> > To: xen-devel@xxxxxxxxxxxxxxxxxxx
> > Subject: [Xen-devel] RFC: automatic NUMA placement
> >
> > Hi,
> >
> > I just stumbled upon the automatic pinning of vcpus on domain creation
> > in
> > case of NUMA.
> > This behaviour is questionable IMO, as it breaks correct handling of
> > scheduling weights on NUMA machines.
> > I would suggest to switch this feature off per default and make it a
> > configuration option of xend. It would make sense, however, to change
> > cpu pool
> > processor allocation to be NUMA-aware.
> > Switching NUMA off via boot option would remove NUMA-optimized memory
> > allocation, which would be sub-optimal :-)
> >
> > What do you think?

Juergen

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Juergen Gross                 Principal Developer Operating Systems
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