Re: -s and -m options

Gregory P. Smith (
Fri, 22 Jan 1999 09:13:32 -0800

> Hi,
> it is clear to me what -m and -M mean. But I am confused about -s and -S. Whe
> re
> is the system default socket size defined? (I run Netperf on IRIX).
> How do the m-options affect the performances ?

The system socket buffer size is the kernel data buffer that data gets
copied out of the application into and queued up to be put on the
wire. The default on most systems is around 64k (Irix in particular
defaults to that). netperf in verbose mode will print what size the
system is using if you don't specify one yourself with -s. For high
performance networks with large packet sizes (ie: HIPPI) it is very
important to increase the socket buffer size so that the kernel has
enough data to keep sending packets within a reasonable TCP window.

As for the netperf command line, it's not obvious. :) Try this:

netperf -h


netperf -- -h

All parameters specific to a particular test type come after the --
parameter. So when you do a -- -h it shows you the help for test
specific parameters which includes the m, M, s & S options...

it is ugly, but it works once you know about it...