Here is a working swap prefetching patch for 2.6.13. I have resuscitated and 
rewritten some early prefetch code Thomas Schlichter did in late 2.5 to 
create a configurable kernel thread that reads in swap from ram in reverse 
order it was written out. It does this once kswapd has been idle for a minute 
(implying no current vm stress). This patch attached below is a rollup of two 
patches the current versions of which are here:

http://ck.kolivas.org/patches/swap-prefetch/

These add an exclusive_timer function, and the patch that does the swap 
prefetching. I'm posting this rollup to lkml to see what the interest is in 
this feature, and for people to test it if they desire. I'm planning on 
including it in the next -ck but wanted to gauge general user opinion for 
mainline. Note that swapped in pages are kept on backing store (swap), 
meaning no further I/O is required if the page needs to swap back out.

Cheers,
Con Kolivas