Messages in this thread | | | Date | Wed, 16 Jan 2008 16:31:37 +0100 | From | Ingo Molnar <> | Subject | Re: nosmp/maxcpus=0 or 1 -> TSC unstable |
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* 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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