2.6.6-1.435: kswapd clears out cache?

[Philip Molter <philip@xxxxxxxxxxxxxx>]

I have a box I recently updated to kernel 2.6.6-1.435 from 2.6.5-1.358. 
 This box has no swap and 4GB of memory.  Normally, when it runs, about 
2.5GB of that memory is consumed by file cache.  This is the desired 
behavior.  After upgrading to 2.6.6-1.435, at least once every five 
minutes, kswapd runs and completely wipes out the file cache.  It's not 
caching other information, it's just completely clearing it out so the 
box has about 2.5GB of memory free.  This isn't desired, because then 
all the stuff that was cached needs to be re-cached, pegging I/O on the 
box and killing performance of our application.

Has anyone else seen this behavior?  Is there something I can do to stop 
it?  I've tried changing the swappiness level to 0 with no affect (I 
didn't expect one since there is no swap).

TIA,
Philip