[netperf-talk] netperf2.4.4 on linux, socket size issue ?

[Andrew Gallatin]

mark wagner writes:
 > above.  So, is the drop in performance because I'm really only using an 
 > 8K buffer even though its getting reported as 16K or is something else 
 > going on here that I'm oblivious to?

The doubling is a red herring.  By default, linux will auto-tune the
socket buffer sizes.  If the application sets the socket buffer size,
this auto-tuning is disabled.   So in your -- -s 8K example, you're
disabling the auto-tuning, and throttling transmit.

BTW, there are some other settings you should tweak for good 10GbE
performance (like increasing the default socket buffer limits).  

Try adding the following lines to
/etc/sysctl.conf and execute the command "sysctl -p /etc/sysctl.conf".

net.core.rmem_max = 16777216
net.core.wmem_max = 16777216
net.ipv4.tcp_rmem = 4096 87380 16777216
net.ipv4.tcp_wmem = 4096 65536 16777216
net.core.netdev_max_backlog = 250000

What NIC are you using?  4Gb/s is very low for 10GbE.


Drew