Re: [RFC] Advanced XIP File System
From: Jan Engelhardt
Date: Wed May 03 2006 - 12:40:49 EST
> What is it?:
> - Borrows much from CRAMFS with Linear XIP patches
Apropos borrowing: borrow the compression from Squashfs.
> I've heard people say, "XIP is stupid. Why on earth would I use
> expensive slow flash instead of cheap fast RAM?"
> [...] If I
> take libfoo.so which is about 2MiB and throw it in JFFS2, it
> compresses to about 1MiB in flash. If I store libfoo.so as an XIP
> file (uncompressed) in XIP CRAMFS or AXFS it takes up 2MiB of flash. That is
> 1MiB extra flash for XIP. But the JFFS2 version would need
> 2MiB of RAM to store that library when used while the XIP system uses
> 0MiB. That means XIP uses +1MiB of flash and -2MiB of RAM for
> libfoo.so. So for any extra flash used for XIP, it can save twice
> that amount of RAM. The end result can be lower cost systems on the
> small end. The secret is to choose what to make XIP and what to
> compress on flash.
If 2 MB of RAM are cheaper [as you say] than 1 MB of Flash, where's the
advantage when XIP uses more flash?
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/