From: Eric Dumazet <redacted>
Date: Thu, 21 Feb 2008 19:51:52 +0100

Following patch directly calls netif_receive_skb() and avoids lot of 
atomic operations.
(atomic_inc(&dev->refcnt), set_and_set_bit(NAPI_STATE_SCHED, &n->state), ...
  atomic_dec(&dev->refcnt)...), cache line ping-pongs on device refcnt, 
but also softirq overhead.

This gives a nice boost on tbench for example (5 % on my machine)

My only concern is stack usage.

Note that packet reception can elicit a response and go all the way
back into this driver and all the way down into netif_receive_skb()
again.  And so on and so forth.

If there is some bug in the stack (ACK'ing ACKs, stuff like that) we
could get into a loop and overrun the kernel stack in no time at all.

So, if anything, this change could make inconvenient errors become
catastrophic and hard to diagnose.