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Date:      Fri, 17 May 1996 17:49:13 -0500 (EST)
From:      "John S. Dyson" <toor@dyson.iquest.net>
To:        terry@lambert.org (Terry Lambert)
Cc:        alc@cs.rice.edu, questions@freebsd.org
Subject:   Re: Size of the Virtual Memory Page
Message-ID:  <199605172249.RAA03013@dyson.iquest.net>
In-Reply-To: <199605172118.OAA20724@phaeton.artisoft.com> from "Terry Lambert" at May 17, 96 02:18:20 pm

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> > I have thought about it (in passing.)  Actually, it could decrease overhead in
> > some cases, at the expense of memory.  8/16K pages *might* be interesting.  The
> > VM and vfs_bio system (after my changes) will have problems with bigger than
> > 16K pages.  I am sure that they could be worked around.  The limitation
> > has to do with the bit-mask that I use for valid and dirtyness being in
> > 512 byte increments.  We have 32bits/word, so that means that 16K is kind
> > of the max (if you ignore long-longs.)  Long-longs would bring it up to
> > 32K.  I would guess that 64K might be cool also, but require a few changes.
> 
> If you do this, *PLEASE* bracket the code with compile-time disablers
> so I don't have to support 16k pages on the PPC.  Thanks.
> 
NO QUESTION about that.  In fact, I would plan to consult with anyone doing
ports to other architectures before making changes of that kind.  I really
don't forsee doing it for at least six months anyway.

John



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