Allocate all bufferpool shards of the same size, regardless of
underlying allocator. This way increase memory usage a bit, but we're
already quite heavy on that, so no big deal.
Change-Id: Icbe09cd2f9b33bc58ab1efe7de293dea00236fec
Use allocators that return memory blocks aligned to the requested size,
instead of generic malloc. This makes it easier to play tricks with the
memory blocks.
Change-Id: Iad4b1127c76e48c2e9b4ad8489118d4883a24f6a