This patch autoregulates the vm_swappiness dial in 2.6.

It sets the swappiness to 0 initially and makes it proportional to the
percentage of physical ram consumed by application pages. This has the effect
of preventing applications from being swapped out if the ram is filling up
with cached data. Conversely, if many applications are in ram the swappiness
increases which means the application currently in use gets to stay in
physical ram while other less used applications are swapped out.