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Date: Sun, 13 Mar 2011 09:02:07 +0200
From: Aragon Gouveia <aragon@phat.za.net>
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Subject: C2/C3 states cause poor TCP performance with re(4)
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Hi,

I've recently been hunting down a TCP performance issue with re(4) on a 
system that has C3 states enabled.  In short, outgoing TCP traffic shows 
good performance, but incoming TCP traffic has very unstable throughput 
with substantial packet loss evident in a tcpdump.

The same was observed with C2 states enabled.  Limiting to C1 states 
brought performance back to normal.

Can anyone confirm if this is reproducible with drivers other than 
re(4)?  Am I expecting too much in the hope of achieving both C3 states 
and good performance out of re(4)?  Any pointers on getting there?

This system is tuned using mav@'s tuning guide:

http://wiki.freebsd.org/TuningPowerConsumption


Thanks,
Aragon