Re: RFC: softint-based if_input

[Taylor R Campbell <campbell+netbsd-tech-kern%mumble.net@localhost>]

   Date: Wed, 20 Jan 2016 17:03:09 +0900
   From: Ryota Ozaki <ozaki-r%netbsd.org@localhost>

   I measured several cases of softint-based if_input implementation
   and other implementations including vanilla and polling-based
   packet processing (POC).

   Here are the results of the measurements (TL;TR):
   https://gist.github.com/ozaki-r/975b06216a54a084debc

I'm having a little bit of a hard time following these graphs.  Can
you explain how I should read them?  E.g., what does

   polling-rx w/o ip_pktq

   RX/TX =  148809 / 148809 pps,   100M / 100Mbps |######### 100.0%
   RX/TX =  253096 / 297597 pps,   170M / 200Mbps |################# 85.0%

mean?

Small concern about your no-ip_pktq patch: with it, you acquire and
release softnet_lock for every packet, whereas without it, the ip_pktq
softintr handler acquires softnet_lock once, processes all packets in
the pcq in a batch, and then releases softnet_lock.  Maybe that's not
an issue since pcq_get already involves atomics, but it stuck out at
me a little bit.