Many thanks for the reply. Just SSH'd onto the machine - yes, Intel Ethernet controller. I'll wait for morning (and for the icicles to disappear) and try the recommended settings in that link, and report back.
a kernel trace also provides interesting data. when I did that on a 4 core i5, the servo thread was using about 200 usec and slept for 800 usec. Its the random incursions that take the servo-thread beyond 1000 usec that are the issue. I don't think Wireshark will show the full picture.
