As noted in the FreeBSD TCP tuning and performance thread here:
http://lists.freebsd.org/pipermail/freebsd-performance/2009-December/003909.html
There seems to be a significant performance drop when using 8.0 vs 7.0
after digging around this seems to be caused by the use of increased
kern.ipc.maxsockbuf
Using the default value ( 262144 ) I see the following iperf results:
iperf -t 10 -c server1 -w 2.5M -l 2.5M
------------------------------------------------------------
Client connecting to db3, TCP port 5001
TCP window size: 65.0 KByte (WARNING: requested 2.50 MByte)
------------------------------------------------------------
[ 3] local 85.236.96.66 port 50848 connected with 85.236.96.42 port 5001
[ ID] Interval Transfer Bandwidth
[ 3] 0.0-10.0 sec 1.09 GBytes 935 Mbits/sec
With anything larger than that the rate drops off significantly e.g. 282144
gives:-
iperf -t 10 -c db3 -w 2.5M -l 2.5M
------------------------------------------------------------
Client connecting to db3, TCP port 5001
TCP window size: 65.0 KByte (WARNING: requested 2.50 MByte)
------------------------------------------------------------
[ 3] local 85.236.96.66 port 25867 connected with 85.236.96.42 port 5001
[ ID] Interval Transfer Bandwidth
[ 3] 0.0-10.0 sec 778 MBytes 651 Mbits/sec
and 302144 we're down to just under half the baseline / line rate
iperf -t 10 -c db3 -w 2.5M -l 2.5M
------------------------------------------------------------
Client connecting to db3, TCP port 5001
TCP window size: 65.0 KByte (WARNING: requested 2.50 MByte)
------------------------------------------------------------
[ 3] local 85.236.96.66 port 12506 connected with 85.236.96.42 port 5001
[ ID] Interval Transfer Bandwidth
[ 3] 0.0-10.0 sec 588 MBytes 492 Mbits/sec
Any ideas why using window sizes above 65K results in such poor performance
on 8.0?
Regards
Steve
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