CPU usage of telnetd

[Charles Hedrick]

The vendor is right.  Telnetd is a pig.  There are some things known
that will speed it up a bit.  If you are using vanilla 4.2, there are
some patches to the pty code that will speed up pty's a lot.  But even
with those patches, telnetd can use a fair amount of CPU time.
Fortunately, in practice people don't sit there typing out files at
9600 baud.  So things aren't as bad as they could be.  I'd try to get
an estimate of the amount of terminal output you do during you peak
load period, and see whether the CPU use is worth attacking.  I could
certainly imagine situations where an Ethernet interface that looks
like a DMF would be a great idea.  Actually, I'd rather see somebody
fix telnetd.  I have talked with people who know the terminal code,
and they conclude that a couple of days work could improve performance
dramatically.  But I can't get them to do it.  grrrrr.......  I have
thought of doing it myself, but it would take me an order of magnitude
longer to do it than a real kernel wizard.