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Date:      Sun, 23 Jun 2002 21:46:16 -0500
From:      Alan Cox <alc@cs.rice.edu>
To:        Peter Wemm <peter@wemm.org>
Cc:        Ian Dowse <iedowse@FreeBSD.org>, cvs-committers@FreeBSD.org, cvs-all@FreeBSD.org
Subject:   Re: cvs commit: src/sys/powerpc/include types.h src/sys/arm/include types.h src/sys/i386/include types.h
Message-ID:  <20020624024616.GF11391@cs.rice.edu>
In-Reply-To: <20020624022343.3FDDB380E@overcee.wemm.org>
References:  <200206232157.g5NLvKF31769@freefall.freebsd.org> <20020624022343.3FDDB380E@overcee.wemm.org>

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On Sun, Jun 23, 2002 at 07:23:43PM -0700, Peter Wemm wrote:
> Ian Dowse wrote:
> > iedowse     2002/06/23 14:57:19 PDT
> > 
> >   Modified files:
> >     sys/powerpc/include  types.h 
> >     sys/arm/include      types.h 
> >     sys/i386/include     types.h 
> >   Log:
> >   Make vm_pindex_t 64-bit on all platforms. This is necessary to avoid
> >   overflows with the large file sizes that UFS2 permits.
> 
> Ouch, is this really necessary?  The whole index::offset thing was
> explicitly to avoid using 64 bit arithmetic here due to the performance
> hit.    Dyson posted some numbers somewhere in the distant past, they can
> probably be found on the archives.
> 
> If this really is necessary, then we may as well strip out the pindex stuff
> entirely and just use 64 bit byte offsets instead of
> "64bit pindex::32bit offset".  ie: why carry a 96 bit synthetic value when
> we only need a 64 bit value?

I agree with this observation.  I've been discussing precisely what you
describe with Ian.

Alan



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