*BSD News Article 90609


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From: doogie@zeus.anet-stl.com (Jason Young)
Newsgroups: comp.unix.bsd.freebsd.misc
Subject: FreeBSD and copy-on-write fork
Date: 8 Mar 1997 01:09:49 GMT
Organization: ANET-Internet Service Provider 1-800-776-8894
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Does FreeBSD have any sort of implementation of or plans for a
copy-on-write fork such as the one Linux uses? I know when Linux
implemented this, it was rather controversial and can result in a speed
hit in some cases. 

However, I have a box here that runs a mud that regularly sits at around a
42MB process size. It forks itself at regular intervals to save a copy of
the database to disk (once every half hour currently). The box has 80MB of
RAM, and with the Linux copy-on-write fork, there is a HUGE win with
respect to memory usage - currently savings of a good 32-33MB of RAM
during this save.

With normal fork, it would get driven pretty well into swap and drag down
the responsiveness of the mud which is an important issue to us.

Myself I don't see the big controversey. If it could be done in such a way
that you could have both and choose - with a kernel recompile or some
other way that the user could pick which suits their usage - then we all
win.

I'm no huge Linux fan, and I'm running FreeBSD 970209-SNAP on my work
machine, home machine, and my quake server here at A-Net. I wouldn't mind
getting FreeBSD on this mud machine also. Anything in progress in this
arena?

-- 
Jason Young
A-Net Technical Staff