linux-next network throughput performance regression

[Eric Dumazet]

On Mon, 2015-11-09 at 20:23 +0000, Simon Xiao wrote:
> Thanks Eric to provide the data. I am looping Tom (as I am looking into his recent patches) and Olaf (from Suse).
> 
> So, if I understand it correctly, you are running netperf with single
> TCP connection, and you got ~26Gbps initially and got ~30Gbps after
> turning the tx-usecs and tx-frames.
> 
> Do you have a baseline on your environment for the best/max/or peak
> throughput?

The peak on my lab pair is about 34Gbits, usually I get this if I pin
the receiving thread on a cpu, otherwise process scheduler can really
hurt too much.

lpaa23:~# DUMP_TCP_INFO=1 ./netperf -H lpaa24 -l 20 -Cc -T ,1
MIGRATED TCP STREAM TEST from 0.0.0.0 (0.0.0.0) port 0 AF_INET to lpaa24.prod.google.com () port 0 AF_INET : cpu bind
tcpi_rto 201000 tcpi_ato 0 tcpi_pmtu 1500 tcpi_rcv_ssthresh 29200
tcpi_rtt 101 tcpi_rttvar 15 tcpi_snd_ssthresh 289 tpci_snd_cwnd 289
tcpi_reordering 3 tcpi_total_retrans 453
Recv   Send    Send                          Utilization       Service Demand
Socket Socket  Message  Elapsed              Send     Recv     Send    Recv
Size   Size    Size     Time     Throughput  local    remote   local   remote
bytes  bytes   bytes    secs.    10^6bits/s  % S      % S      us/KB   us/KB

 87380  16384  16384    20.00      33975.99   1.27     3.36     0.147   0.389  

Not too bad, I don't recall reaching more than that ever.