irq load when servicing ethernet

[Wojciech Puchar]

is it normal on AMD64 machine to have 10-15% CPU time spent in "interrupt" 
by sending file at 7MB/s by ftp to other machine?

fxp0: <Intel 82551 Pro/100 Ethernet> port 0xec00-0xec3f mem 
0xfbfff000-0xfbffffff,0xfbfc0000-0xfbfdfff
f irq 17 at device 5.0 on pci2


nothing else uses irq 17

systat shows 3000 ints/s, with 1.8GHz CPU it's like 60000-90000 CPU clocks 
per  single interrupt service.
at least - TOO MUCH.

with much higher traffic over hard drive interrupt percentage is below 1% 
if measurable at all.