qht: QEMU's fast, resizable and scalable Hash Table

qht: QEMU's fast, resizable and scalable Hash Table

This is a fast, scalable chained hash table with optional auto-resizing, allowing
reads that are concurrent with reads, and reads/writes that are concurrent
with writes to separate buckets.

A hash table with these features will be necessary for the scalability
of the ongoing MTTCG work; before those changes arrive we can already
benefit from the single-threaded speedup that qht also provides.

Signed-off-by: Emilio G. Cota <[email protected]>
Message-Id: <1465412133[email protected]>
Signed-off-by: Richard Henderson <[email protected]>