Weirdness - FBSD 7, Routing, Packet generator, em taskq

[Andrew Snow]

Firstly, tried turning off polling?  Some of us have found it to be 
detrimental to performance on the more modern systems.  Its use was more 
practical on older systems were servicing interrupts took alot of CPU 
power, but the "em" driver supports delaying interrupts until more 
packets have arrived - see the sysctls available on the em man page.

So you're probably better of turning off polling and playing with these 
tunables, by calculating how many packets you're likely to be able to 
fit in the tx/rx descriptor array before you need to generate an interrupt.

Secondly try pressing shift+c inside top to display "raw cpu usage" 
instead of the default "weighted cpu usage".

Finally, is your test portraying realistic conditions?  I am reminded 
that 1GB/s with 1500 MTU is only roughly 80,000 pps.



- Andrew