rwhod

[cball at ishmael]

>karl at triceratops.cis.ohio-state.edu.U writes:
>>roy at phri.UUCP (Roy Smith) writes:
>>   The N^2 effect isn't so bad when you've got
>>   15 or 20 machines, but it kills you when you've got hundreds.  My
>>   idea was to make rwhod write into /usr/lib/rwho instead of
>>   /usr/spool/rwho.

>Better, run an rwhod which doesn't broadcast at all, but rather [a]
>NFS-mount /usr/spool/rwho from a single server, and then [b] just
>scribbles /usr/spool/rwho/its-own-name.  Poof, no more broadcasts at
>all.

I have an rwhod(called lwhod) that does exactly this and works with Suns
and Vaxes.  I didn't use licensed sources so it's available, if there's
any interest.

While rwhod is a pig, I don't think it is really N**2.  More like W**N
where W is the number of workstations/server.  With 200 workstations
and a maximum of 10 diskless nodes/server the number should be less 
than 12 interrupts/sec(significant, but not enough to swamp a system).
I suspect that there is a quantum syncronization effect when lots of
machines boot simultaneously.  Synronization probably even increases
over time due to scheduling anomalies since rwhod wakes up on both 
sleep and remote packet events.  As written, I think rwhod would work
better if it slept some fixed time plus a random constant.

Charles Ball
Intermetrics, Inc.
cball at inmet.inmet.com
uunet!inmet!cball