if_em and ip aliases

[Peter Avalos]

I noticed last night that it takes over 3 seconds to add an ip alias on this
driver.  While it's bringing up the alias, the kernel is unresponsive.
After discussing this with Hiten, he made a patch that brought our driver in
sync with FreeBSD.  Here's a link:

http://www.sublimic.com/~hmp/dragonfly/if_em+integ.diff

After this patch I was able to bring up 254 aliases in about 73 seconds.
This is much better than the previous behavior, but still it's dismally
slow.  It takes about 1 second to bring up 254 aliases on an fxp card.

I don't have a FreeBSD 4.9 machine with this type of NIC to see if the same
behavior exists.  It does appear that the patched version of the driver
performs the same as FreeBSD 5.2.1, and that's why I've cc'd Prafulla
Deuskar.

Is anyone else able to reproduce this?