svn commit: r285973 - head/sys/dev/bxe

[John Baldwin]

On Tuesday, July 28, 2015 07:15:45 PM David C Somayajulu wrote:
> Author: davidcs
> Date: Tue Jul 28 19:15:44 2015
> New Revision: 285973
> URL: https://svnweb.freebsd.org/changeset/base/285973
> 
> Log:
>   - Avoid lock contention in the if_transmit callback by using trylock and
>    enqueueing the frames when it fails. This way there is some latency
>    removed from the transmitting path.

Most drivers that used to do this have stopped doing it do to the race
that if you have bursty traffic you can end up with packets delayed
until another packet is transmitted.  If you are always blasting traffic
non-stop, that's fine.  If you have bursty traffic, it's not so great.

A real-life scenario I had with igb(4) resulted in packets delayed by
a full second.

-- 
John Baldwin