[Beowulf] Re: typical latencies for gigabit ethernet

Dave Love d.love at liverpool.ac.uk
Tue Jun 30 09:07:59 EDT 2009

Patrick Geoffray <patrick at myri.com> writes:

> Instead of rx-usecs being the time between interrupts, it is sometimes 
> implemented as the delay between the the first packet and the following 
> interrupt, which is obviously wrong.

Ah.  Is that likely to be in the driver, where it might be fixed, or the
NIC firmware?

> rx-frames may generate an interrupt storm if you receive a stream of 
> small packets. You may want to measure how many interrupts per second 
> are produced in this case, compared to using rx-usecs.

Yes, but I'm not sure how useful that is since the rx-usecs adjustment
doesn't seem sensible in this case.  Also I'm not actually interested in
tg3 for production use, so maybe someone who is would like to try.
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