Uh oh - Kernel VM space is limited! So, we changed the world so that only in-use buffers are mapped into kernel memory. -Allow buffer cache to grow dynamically. -Change the Page Daemon to steal memory from the cache when needed. -Map buffers only when in use. -Now need to potentially wait for kva, and for physmem. -Challenging as this adds interesting wait states to the kernel - took quite a while to get right.