The kernel’s memory-management subsystem goes to great lengths to keep the
pages that are actually in use in memory. But sometimes it gets things
wrong, leading to reduced performance or, in the worst cases, flat-out
thrashing. We may be about to see a significant improvement, though,
thanks to a
patch set from Joonsoo Kim changing how anonymous pages (those
containing data not backed by files on disk) are managed.
As it turns out, all that had to be done was to make use of some work that
already exists in related parts of the memory-management code.

Source: LWN.net – [$] Working-set protection for anonymous pages