Re: Can jffs2 support XIP extensions?

[Joshua Wise <joshua@joshuawise.com>]

> For the kernel boot time it's true that boot times tend to be dominated 
> by the decompression step.  I measured this on a couple platforms at one 
> point (some of my measurements may have been in the OLS presentation, 
> not sure).  I didn't directly measure kernel boot times of an 
> uncompressed non-XIP kernel, but would roughly guess an uncompressed 
> non-XIP kernel would boot to /sbin/init in only about a few tens of 
> milliseconds more time (I'm guessing about the increased time to copy an 
> uncompressed tetx image to RAM) than an XIP kernel on a 266MHz PowerPC 
> 405LP, and 168MHz OMAP ARM 926T is probably similar (it seems to better 
> deal with the cache effects).
Also remember that on many systems, flash is a lot slower than RAM, so 
it is entirely possible that an XIP kernel would actually be _SLOWER_ 
than non-XIP!

joshua