[$] Slabs, sheaves, and barns

The kernel's slab allocator is responsible for the allocation of small
(usually sub-page) chunks of memory. For many workloads, the speed of
object allocation and freeing is one of the key factors in overall
performance, so it is not surprising that a lot of effort has gone into
optimizing the slab allocator over time. Now that the kernel is down to a single slab allocator, the
memory-management developers have free rein to add complexity to it; the
latest move in that direction is the per-CPU
sheaves patch set from slab maintainer Vlastimil Babka.