Subject: Re: [PATCH net-next] udp/v6: prefetch rmem_alloc in udp6_queue_rcv_skb()

From: Jesper Dangaard Brouer <[email-masked]>
Date: Thu, 22 Jun 2017 22:49:57 +0200

On Thu, 22 Jun 2017 15:01:22 +0200
Paolo Abeni <[email-masked]> wrote:

> very similar to commit dd99e425be23 ("udp: prefetch
> rmem_alloc in udp_queue_rcv_skb()"), this allows saving a cache
> miss when the BH is bottle-neck for UDP over ipv6 packet
> processing, e.g. for small packets when a single RX NIC ingress
> queue is in use.
> 
> Performances under flood when multiple NIC RX queues used are
> unaffected, but when a single NIC rx queue is in use, this
> gives ~8% performance improvement.
> 
> Signed-off-by: Paolo Abeni <[email-masked]>

Testing IPv4 UDP on top of this patch, with ip_early_demux enabled.
I'm impressed, we can now to almost 3 Mpps UDP (across two CPUs) :-)))
Last time I tested on this machine it was around 2.3Mpps.

Good work Paolo! :-)

[jbrouer@skylake src]$ sysctl net/ipv4/ip_early_demux=1
net.ipv4.ip_early_demux = 1
[jbrouer@skylake src]$ 
[jbrouer@skylake src]$ sudo taskset -c 2 ./udp_sink --port 9 --count $((10**6)) --repeat 1000 --recvmsg --connect
          	run      count   	ns/pkt	pps		cycles	payload
recvmsg   	run:  0	 1000000	341.62	2927192.65	1369	18	 demux:1 c:1
recvmsg   	run:  1	 1000000	350.81	2850569.36	1406	18	 demux:1 c:1
recvmsg   	run:  2	 1000000	352.18	2839478.74	1411	18	 demux:1 c:1
recvmsg   	run:  3	 1000000	341.43	2928871.10	1368	18	 demux:1 c:1
recvmsg   	run:  4	 1000000	350.65	2851810.35	1405	18	 demux:1 c:1
recvmsg   	run:  5	 1000000	350.91	2849751.29	1406	18	 demux:1 c:1
recvmsg   	run:  6	 1000000	342.68	2918138.00	1373	18	 demux:1 c:1
recvmsg   	run:  7	 1000000	351.37	2845969.40	1408	18	 demux:1 c:1
recvmsg   	run:  8	 1000000	351.07	2848452.09	1407	18	 demux:1 c:1

https://github.com/netoptimizer/network-testing/blob/master/src/udp_sink.c

-- 
Best regards,
  Jesper Dangaard Brouer
  MSc.CS, Principal Kernel Engineer at Red Hat
  LinkedIn: http://www.linkedin.com/in/brouer