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

Greg Ungerer
2008-08-25T06:35:40Z

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@snapgear.com
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