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SubjectRe: nosmp/maxcpus=0 or 1 -> TSC unstable

* Pete Wyckoff <pw@osc.edu> wrote:

> > pretty sure this is the culprit is that num_possible_cpus() > 1,
> > which would mean cpu_possible_map contains the second cpu... but i'm
> > not quite sure what the right fix is... or perhaps this is all
> > intended.
>
> We've seen the same problem. We use gettimeofday() for timing of
> network-ish operations on the order of 10-50 us. But not having the
> TSC makes gettimeofday() itself very slow, on the order of 30 us.

30 usecs is too much - even with pmtimer it's typically below 5 usecs.
Could you run this on your box:

http://people.redhat.com/mingo/time-warp-test/time-warp-test.c

and send back what it reports? (run it for a few minutes)

Ingo


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