On Mon, 2014-06-30 at 09:42 -0700, Tom Herbert wrote:

Eliminating a couple of conditionals is a nice logic improvement, but
is not material in the performance improvement. The improvement comes
for the fact that we are staying in the the process_backlog loop and
not clearing napi_state as long as there is still work to do. This can
result in fewer IPIs which is shown in number of interrupts/sec.
(1145382 vs. 1021674 in my test).

The cost of the change is one additional lock and check on qlen when
the queue is empty, however in this case they should still be in the
local cache so that's not overly expensive (far cheaper than more
IPIs).

Great, thanks !