[MUD-Dev] Re: MUD Development Digest

J C Lawrence claw at under.engr.sgi.com
Wed Apr 8 18:48:48 New Zealand Standard Time 1998


On Sun, 5 Apr 1998 23:46:12 PST8PDT 
Nathan F Yospe<yospe at hawaii.edu> wrote:

> On IRIX, go ahead and use them, you might not be able
> to tell if they are threads or processes (sorry, J C, but that's
> been my experience), and on Linux... pray. Can't speak for the
> others.

Don't mind the fact that I'm at SGI.  I'm a contractor.  My current
assignment happens to be at SGI.  A couple months ago I was at Sun.  A
few before that at HP, Charles Schwab etc.  They pay -- I have fun.
Its a good deal.  I'm rarely a devotee.

There are several thread models.  Threads can range from nearly
full-weight processes to very very light weight user-space items with
most (if not all) of their scheduling handled by the application.

Yes, even MOO or Cold with its internal spin loop is, sorta,
multi-threaded.

Linux's current thread model seems to be based on hacking fork() such
that the new process (and yes, it is a full weight process) does not
mark the data segment as COPY-ON-WRITE.  Note: The normal fork() call
does so mark the data segment, resulting in any attempted writes to
the data segment by the new process causing the entire DS to be copied
for the new process.

NT (IIRC, no source data) has a concept of "fibres" which are very
light weight user-space threads (don't know how scheduling is handled,
but its not classic kernel style).  NT's normal threading model is a
fairly standard kernel threads model (much heavier weight) where
threads compete for the process'es time-slices (IIRC).  

I don't have enough data or understanding of the Java, Solaris, or
Irix thread models to comment in particular there (tho I am becoming
sufficiently impressed with SGI hardware that I may just port in that
direction and find out: you can get a nicely dresed Indy for ~$2K
hereabouts, and Indigos run $700-ish ('course I want an O2, but that's
life)).

--
J C Lawrence                               Internet: claw at null.net
(Contractor)                               Internet: coder at ibm.net
---------(*)                     Internet: claw at under.engr.sgi.com
...Honourary Member of Clan McFud -- Teamer's Avenging Monolith...



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