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RE: [Xen-devel] Linux 2.6.11 does not build SMP

On Mon, 14 Mar 2005, Ian Pratt wrote:

> Guys, just remember that SMP is certainly not ready for putting in front
> of users yet.

It's been enabled in Fedora Rawhide for a few months now,
and doesn't seem to be giving much trouble at all, at
least not stability wise.

> If someone's looking for some work to do to help SMP support, it would
> be great if you could look into out-of-lining all the spinlocks, and
> then writing some code to no-op them if there's only one CPU currently
> active. This would elminate most of the overhead of an SMP vs uni
> kernel, which would certainly be great for us (as well as for vendor
> kernels). 

I'll take a look.  Another thing to do would be yielding
the CPU on spinlock contention, in case there are other
virtual CPUs that want to run.

The timer also causes lots of fun, with many of these
every day.  This doesn't cause any stability problems I
can see, though - it's just the timer detecting that
something went wrong and bailing out.

Timer ISR/1: Time went backwards: -410090000 118469090000000 9910000 11846909000

"Debugging is twice as hard as writing the code in the first place.
Therefore, if you write the code as cleverly as possible, you are,
by definition, not smart enough to debug it." - Brian W. Kernighan

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