how to saturate 100Mbit

[Clark Gaylord]

Eugene Grosbein wrote:
> Is it possible to saturate 100Mbit ethernet using FreeBSD 4.9-STABLE,
> Pentium-133 & Intel 430VX-based motherboard (PCI-33),
> Intel 82559 Pro/100 Ethernet (fxp) ? 
> 
> I tried to use sendfile(2) on /dev/zero but that does not work.
> Then I created 8Tb holey file and used sendfile() on it.
> That gave 100% CPU load and only 37Mbit/s on wire.

I usually use ttcp for tcp throughput measurement.  You may not be able 
to do 100Mbps, due to tcp-ness, but it has a udp mode as well.  Depends 
on what you are interested in doing.  But ttcp is pretty low impact. 
Also, when you use it, boost the buffersize; this can help performance 
(and lower cpu hit) considerably.

I am doing 800+Mbps on gigE with FreeBSD 5.1 these days.  The other 
trick we use for link utilization with tcp is to multiplex several 
sessions; we do a few score (or a few hundred :-) simultaneous ttcp's 
just with a shell script and background the processes.

ping -f with larger packets can also be useful.

--ckg