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Re: Opinions on packaging ATLAS (for the x86 architecture)



On Wed, Oct 07, 2009 at 11:29:11AM -0400, Bill Nottingham wrote:
> Richard W.M. Jones (rjones redhat com) said: 
> > Yup.  The really fun starts when you do live migration.  The processor
> > literally changes underneath the running programs.  If you thought you
> > had SSE3 one minute, then the next you don't, or vice versa.
> > 
> > No one has to my knowledge come up with a good way to deal with this.
> > But it probably involves signalling the kernel and processes so that
> > they can redo processor detection.  You can see why that is not going
> > to be pleasant.
> 
> Surely the way to do this is to know what your workload is doing,
> and not do live migration to random hardware? 

But we're talking -- in this very thread -- about the case where core
programs are starting to use SIMD instructions.  This is only going to
get more common because the only way to use a large proportion of the
compute power of modern processors is to use these instructions.

And in any case, the kernel is using them for checksumming and so on,
even if you can be absolutely sure your workload isn't.

As I said in my earier reply:

> > However that reduces the utility of the hardware and makes system
> > administration more complex.

OR we can use all the power of modern hardware and make system
administration easier.

Rich.

-- 
Richard Jones, Emerging Technologies, Red Hat  http://et.redhat.com/~rjones
libguestfs lets you edit virtual machines.  Supports shell scripting,
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