[patch][lagg] - Set a better granularity and distribution on roundrobin protocol.

[Marcelo Araujo]

Hello guys,

I made some changes on roundrobin protocol where from now you can via
sysctl(8) set a better packets distribution among the interfaces that are
part of the lagg(4) group.

My motivation for this change was interfaces that use TSO, as example
ixgbe(4), the performance is terrible, as we can't full fill the TSO buffer
at once, the throughput drops expressively and we have much more sack
between hosts.

So, with this patch we can set the number of packets that will be send
before switch to the next interface.

In my testbed using ixgbe(4), I had a very good performance as you can see
bellow:

1) Without patch:
------------------------------------------------------------
Client connecting to 192.168.1.2, TCP port 5001
TCP window size: 32.5 KByte (default)
------------------------------------------------------------
[  3] local 192.168.1.1 port 32808 connected with 192.168.1.2 port 5001
[ ID] Interval       Transfer     Bandwidth
[  3]  0.0- 1.0 sec   406 MBytes  3.40 Gbits/sec
[  3]  1.0- 2.0 sec   391 MBytes  3.28 Gbits/sec
[  3]  2.0- 3.0 sec   406 MBytes  3.41 Gbits/sec
[  3]  3.0- 4.0 sec   585 MBytes  4.91 Gbits/sec
[  3]  4.0- 5.0 sec   477 MBytes  4.00 Gbits/sec
[  3]  5.0- 6.0 sec   429 MBytes  3.60 Gbits/sec
[  3]  6.0- 7.0 sec   520 MBytes  4.36 Gbits/sec
[  3]  7.0- 8.0 sec   385 MBytes  3.23 Gbits/sec
[  3]  8.0- 9.0 sec   414 MBytes  3.48 Gbits/sec
[  3]  9.0-10.0 sec   515 MBytes  4.32 Gbits/sec
[  3]  0.0-10.0 sec  4.42 GBytes  3.80 Gbits/sec

2) With patch:
------------------------------------------------------------
Client connecting to 192.168.1.2, TCP port 5001
TCP window size: 32.5 KByte (default)
------------------------------------------------------------
[  3] local 192.168.1.1 port 10526 connected with 192.168.1.2 port 5001
[ ID] Interval       Transfer     Bandwidth
[  3]  0.0- 1.0 sec   694 MBytes  5.83 Gbits/sec
[  3]  1.0- 2.0 sec   999 MBytes  8.38 Gbits/sec
[  3]  2.0- 3.0 sec  1.17 GBytes  10.1 Gbits/sec
[  3]  3.0- 4.0 sec  1.34 GBytes  11.5 Gbits/sec
[  3]  4.0- 5.0 sec  1.15 GBytes  9.91 Gbits/sec
[  3]  5.0- 6.0 sec  1.19 GBytes  10.2 Gbits/sec
[  3]  6.0- 7.0 sec  1.08 GBytes  9.23 Gbits/sec
[  3]  7.0- 8.0 sec  1.10 GBytes  9.45 Gbits/sec
[  3]  8.0- 9.0 sec  1.27 GBytes  10.9 Gbits/sec
[  3]  9.0-10.0 sec  1.39 GBytes  12.0 Gbits/sec
[  3]  0.0-10.0 sec  11.3 GBytes  9.74 Gbits/sec

So, basically we have a sysctl(8) called "net.link.lagg.rr_packets" where
we can set the number of packets that will be send before the roundrobin
move to the next interface.

Any comment and review are very appreciated.

Best Regards,

-- 
Marcelo Araujo            (__)araujo at FreeBSD.org
\\\'',)http://www.FreeBSD.org <http://www.freebsd.org/>   \/  \ ^
Power To Server.         .\. /_)
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