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Date:      Sun, 17 May 1998 21:00:38 +0000 (GMT)
From:      Terry Lambert <tlambert@primenet.com>
To:        toor@dyson.iquest.net (John S. Dyson)
Cc:        tlambert@primenet.com, eivind@yes.no, wollman@khavrinen.lcs.mit.edu, current@FreeBSD.ORG
Subject:   Re: cvs commit: src/sys/conf param.c src/sys/kern uipc_domain.c uipc_proto.c uipc_socket.c uipc_socket2.c uipc_usrreq.c src/sys/
Message-ID:  <199805172100.OAA29938@usr05.primenet.com>
In-Reply-To: <199805162247.RAA05770@dyson.iquest.net> from "John S. Dyson" at May 16, 98 05:47:25 pm

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> > The protection you would gain is statistical; there would still be
> > failure races if you did it (consider a low memory condition; just
> > because you can expand the page mappings doesn't mean that you will
> > have pages available for them to point to).
> > 
> > This is why type stable memory is so annoying.  8-).
>
> You haven't made any arguments for or against type stable memory.  Limited
> memory size is annoying, but a fact of life.  The code can be made to be
> dynamic, but the critical region issues become challenging.

TSM prevents page migration of the type you would need to have,
assuming you don't use a "handle" pointer and/or segment identifier,
should you need to expand a region without preallocating a large
number of anonymous pages that you could "type-commit" at interrupt
time.

This isn't really intended to be an argument against TSM (an idea which
I support), just a note that it makes some things more annoying to
implement.


					Terry Lambert
					terry@lambert.org
---
Any opinions in this posting are my own and not those of my present
or previous employers.

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