From mboxrd@z Thu Jan  1 00:00:00 1970
From: Alex Riesen <raa.lkml@gmail.com>
Subject: Re: First cut at git port to Cygwin
Date: Sat, 8 Oct 2005 20:49:25 +0200
Message-ID: <20051008184925.GA6347@steel.home>
References: <81b0412b0510060205v4cd510c9wb4b06a3ed9242c8@mail.gmail.com> <81b0412b0510060307q431b64edt4196553bce28346c@mail.gmail.com> <81b0412b0510070544v3e7cf0b4n521db8ff7e4e335a@mail.gmail.com> <Pine.LNX.4.64.0510070828270.31407@g5.osdl.org> <20051007205450.GA14827@steel.home> <20051007212250.GA1423@steel.home> <4346E8AC.5030503@citi.umich.edu> <20051007213952.GA8821@steel.home> <Pine.LNX.4.64.0510080900510.31407@g5.osdl.org> <Pine.LNX.4.63.0510082023130.25971@wbgn013.biozentrum.uni-wuerzburg.de>
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To: Johannes Schindelin <Johannes.Schindelin@gmx.de>
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Johannes Schindelin, Sat, Oct 08, 2005 20:27:06 +0200:
> > I really think that you should just get rid of the mmap.
> > 
> > As it is, you're just slowing the code down on sane architectures. That's 
> > not good.
> > 
> > So I'd suggest something like this instead.
> > 
> > Totally untested, of course.
> 
> Am I missing something? I don't see where the changes are written back to 
> the fd. After all, mmap() is called with PROT_WRITE...

It's just becase the file is open for reading only.
Also, it is not an mmap/unmap implementation. Just reading cache in.