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RE: MP locking?

> > ...
> > You need memory barriers, modern CPUs can do speculative reads, and
> some
> > can reorder writes. AFAIK, lock operations act as memory barriers.
> > atomic ops do not.
> With my PAT patch you can map a page uncached. This disables
> speculative accesses.

If other mechanisms are available to get the right synchronization or
ordering of visibility, that's generally better.  Depending on the
machine, uncached can have other side effects you might not want.  And
it certainly is likely to have a significant performance impact.


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