Process creation & "swap"

[Wayne Throop]

>    I have been told that Data General's AOS creates new
> processes *first* in the "swap space" on disk and *then*
> transfers a copy to memory.
> 
>    My question:  what does (2.9) UN*X do?  Does it create the
> process (text, data, ...) in memory , transferring it to
> "swap" only if necessary?  Or does it use the AOS approach?
> 
>    Kenneth H. Jacker
>    Dept of Math Sciences
>    Appalachian State Univ     ...!{decvax,akgua}!mcnc!ecsvax!khj

Good greif! How did this base canard get circulated?  It does make
an interesting theory as to why AOS and AOS/VS process creation is
slower than process creation on Unix(tm) on the same hardware, but it is
TOTALLY UNTRUE.  In particular, AOS/VS, like most sane virtual memory
systems, creates a mostly empty logical address space for newly
created processes, and then faults pages in from the executable on demand,
for both "text" and "data".  I'm not so sure about the innards of
Berkeley or other VM systems, but I rather think they do likewise.

And please, all you folks out there, if you are going to run down
AOS or AOS/VS, please have the courtesy to run it down for
something it is guilty of. :-)
-- 
Wayne Throop at Data General, RTP, NC
<the-known-world>!mcnc!rti-sel!rtp47!throopw