> How do you do that from userspace, atomically? A counter in the shared
> page?
Yup. You need some shared data for the TSC offset such anyways, so
moving the context switch counter onto such a page won't be much of
a problem. Using the %tr trick to get the CPU number would allow for
some of these data structures to be per-cpu without incurring any LOCK
overhead, too.
-ben
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