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From: radzy@calma.UUCP (Tim Radzykewycz)
Newsgroups: net.arch
Subject: Re: TLB entry invalidation
Message-ID: <115@calma.UUCP>
Date: Wed, 1-Jan-86 10:59:11 EST
Article-I.D.: calma.115
Posted: Wed Jan  1 10:59:11 1986
Date-Received: Thu, 2-Jan-86 04:59:41 EST
References: <1730@uw-beaver> <2619@sjuvax.UUCP> <867@x.UUCP> <2659@sjuvax.UUCP>
Reply-To: radzy@calma.UUCP (Tim Radzykewycz)
Followup-To: junk
Distribution: net
Organization: GE/Calma Co., R&D Systems Engineering, Milpitas, CA
Lines: 36

In article <2659@sjuvax.UUCP> jss@sjuvax.UUCP (J. Shapiro) writes:
>Intel does not have a clear TLB instruction *or* pin, and as such, if
>one processor robs another of a page belonging to the running process
>you are in deep dip.

With a reasonable multi-processor design, whenever one processor runs
the page scrounging demon, and it finds a page to scrounge, then
that processor can cause a "special" interrupt on all of the processors.
This would cause each of the other processors to perform a context
switch, which would clear the TLB.  The "special" interrupt wouldn't
really do anything except cause the double context switch.

This is a rather poor way of designing the system, because this
method of invalidating a page is very costly, but at least it
is possible to design a multi-processor system around the 286
if that is a design goal.

>... Besides, on a real system
>one wants sbrk to be a priviledged system call,  ....

>Exec is a system call - I certainly wouldn't want a nonpriviledged
>process to perform it.  Similarly fork.

This is krock.  It sounds to me like J. Shapiro doesn't want *any*
process that isn't SUID ROOT to do *any* system call.  Totally
unrealistic.

begin :-) mode
Or maybe he means that if the process is "priviledged" to run on
the system, it can do a system call.
end :-) mode

-- 
Tim (radzy) Radzykewycz, The Incredible Radical Cabbage.
	calma!radzy@ucbvax.ARPA
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