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

On Wed, Oct 07, 2009 at 08:19:07PM +0200, Ralf Ertzinger wrote:
> Hi.
> On Wed, 7 Oct 2009 19:10:28 +0100, Richard W.M. Jones wrote
> > If it's possible to write programs and shared library loaders so that
> > redetection can be performed mid-execution, then prefer that method
> > over one which only detects hardware when the program starts up.
> I have no qualms whatsoever with hardware changing between boots.
> Network cards, hard disks, CPU features, you name it. But having
> CPU features change from one instruction to the other (which the 
> above would suggest, correct me if I'm wrong)... how do you suggest
> this would work? Testing for the feature before using it (every time?
> That should nullify any speedup gained by using the features in
> the first place) does not work, because the machine may move between
> the test and the instruction (maybe there's a way around this).

I didn't say I had a way to do it, but in my earlier post I said
perhaps one could send a special migration signal to the process.
I've honestly no idea if that would work.


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.


Richard Jones, Emerging Technologies, Red Hat  http://et.redhat.com/~rjones
virt-top is 'top' for virtual machines.  Tiny program with many
powerful monitoring features, net stats, disk stats, logging, etc.

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