On Mon, 2013-11-04 at 12:29 +0800, Herbert Xu wrote:

On Sun, Nov 03, 2013 at 08:23:02PM -0800, Eric Dumazet wrote:

quoted

Well, GRO adds latencies for sure.

You seem to assume the transmit only can happen when NAPI is done, but
its not true. As soon as GRO fills one packet (reaches max capacity),
packet is delivered and forwarded, even if NAPI handler is not yet
complete for the flow.

Have you actually measured this? The latency added by GRO is pure
processing overhead.  This is tiny when compared to the time NAPI takes
to wait.

Please take a look at 

2e71a6f8084e net: gro: selective flush of packets