I recall some discussion years ago about doing some good system tuning via "systune" parameters, but many of those discussions were over my head at the time (and frankly still over my head grrrrrr)
Here is what I consider a "must change" parameter - ncargs
It appears we want this to be the max possible value - I wasn't able to list contents of a dir and I also wasn't able to compile openssl because I was getting an error from the shell "argument list to long". Modifying this value to its max value helps this problem go away.
Anyone knows of any other very favorable systunes? It might be good to start compiling a list...
I came across this site
http://mi.eng.cam.ac.uk/~rwp/stradx7.3/systune.html, but here are the contents because its also basically a guide to use systune:
Raising the maxlkmem limit
This is something your System Administrator will need to do. We recommend following these instructions to raise maxlkmem to the maximum possible value.
Become root
Type "systune -i"
Type "maxlkmem". It should tell you the current value of maxlkmem in pages. By default it's usually 2000.
Type "maxlkmem 100000", where 100000 pages should be more than the amount of RAM on your machine (a page is usually either 4K or 16K). When asked to confirm, type "y".
The change will fail, but when you type "maxlkmem" again, you will see that the number of pages has increased to approximately three quarters of the RAM installed in the computer. Remember this number of pages, call it N.
Type "maxlkmem N", where N is the number recorded above. Again type "y" when asked to confirm. This time the change will succeed.
Type "maxlkmem" just to make sure!
Type "quit" to exit systune.
Check that the new value of maxlkmem has been correctly recorded in /var/sysgen/stune.
Check that nobody is doing anything on your machine, then reboot your machine by typing "/etc/reboot". This will move /unix.install to /unix and start you running on the new kernel.
For further information read the introduction to Section 2 of the manual (type "man 2 intro"). Alternatively, look in the book on "IRIX Admin: System Configuration and Operation", which is part of the Insight Guide (type "insight"). The relevant sections are titled System Performance Tuning and IRIX Kernel Tunable Parameters.