Path: utzoo!attcan!uunet!cbmvax!jesup
From: jesup@cbmvax.UUCP (Randell Jesup)
Newsgroups: comp.sys.amiga
Subject: Re: Amiga UNIX
Message-ID: <4134@cbmvax.UUCP>
Date: 29 Jun 88 00:44:12 GMT
References: <23602@hi.unm.edu> <4071@cbmvax.UUCP> <142@ssdis.UUCP> <4109@cbmvax.UUCP> <146@ssdis.UUCP>
Reply-To: jesup@cbmvax.UUCP (Randell Jesup)
Organization: Commodore Technology, West Chester, PA
Lines: 26

In article <146@ssdis.UUCP> gsarff@ssdis.UUCP (gary sarff) writes:
>In article <4109@cbmvax.UUCP>, jesup@cbmvax.UUCP (Randell Jesup) writes:
>> >process or task control block, a stack, a heap, a place to store its
>> >registers when it is context switched etc, just like a heavy process.  Only
>> >if the process is really executing multiple threads of itself do you get
>> >any advantage at all.

>> 	This sounds an awful lot like copy-on-write in software.  What happens
>> if one of the threads does an exec()?

>If one of the threads did an exec you would need some kind of copy-on-write
>either hardware or software.  My point was that I have seen a great many
>statements like "unix processes are heavy, amiga's processes are light so 
>ours are better".  I was just making the point that threads buy you little
>"lightness" if there is only one process per thread.

	You're mixing up "light" processes (aka small switching overhead),
with "threads" (some sort of term from mach(?) for multiple subtasks of a
process in the same "heavy" unix process).  We have light processes, i.e.
the task switching overhead is very small compared to most Uni.  We CAN
have threads, if the programmer wants to use them (CreateProc, AddTask).
And some programs do.  But the overhead for a "thread" is the same in
AmigaDos as the overhead for a process.

-- 
Randell Jesup, Commodore Engineering {uunet|rutgers|allegra}!cbmvax!jesup