linux-kernel - Re: [PATCH 00/10] AXFS: Advanced XIP filesystem

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Message-ID: <48B2529B.8030906@snapgear.com>
Date:	Mon, 25 Aug 2008 16:35:07 +1000
From:	Greg Ungerer <gerg@...pgear.com>
To:	Jared Hulbert <jaredeh@...il.com>
CC:	Jamie Lokier <jamie@...reable.org>, Linux-kernel@...r.kernel.org,
	linux-embedded@...r.kernel.org,
	linux-mtd <linux-mtd@...ts.infradead.org>,
	Jörn Engel <joern@...fs.org>,
	tim.bird@...sony.com, cotte@...ibm.com, nickpiggin@...oo.com.au
Subject: Re: [PATCH 00/10] AXFS: Advanced XIP filesystem


Hi Jared,

Jared Hulbert wrote:
>> That would be enough I think. If you could manually select
>> which files are contiguous-and-uncompressed that would be
>> useful for some too here.
> 
> So.... If you don't have an MMU when do you call ->fault?  Does the
> noMMU code just loop through ->fault()ing all the pages in an mmap()?

Sort of. It actually just uses a single ->read to bring in
the entire file contents. There is a few limitations on the use
of mmap() for non-mmu. Documentation/nommu-mmap.txt gives
more details. With no MMU it does rely on being able to kmalloc()
a single RAM region big enough to hold the entire file.


>> One thing for sure is that many people who do non-MMU setups
>> are interested in XIP to get the space savings. These are very
>> often small devices with very constrained RAM and flash. (For
>> whatever it is worth single NOR flash only boards are common in
>> these smaller form factors :-)
> 
> True.

Regards
Greg


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Greg Ungerer  --  Chief Software Dude       EMAIL:     gerg@...pgear.com
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