mv mutex cleanup

Status

• merged to master
• code complete May 4, 2014
• development started April 30, 2014

History / Context

Each database / vnode in leveldb contains a mutex that protects the table file (.sst) management structures. Alll user activity must briefly acquire the mutex before a Read, Write, or Iterator operation. The background compactions must also briefly acquire the mutex before and after a compaction. This branch addresses two scenarios where a background compaction might hold the mutex for an extended time during heavy disk activities. Holding the mutex during compaction blocks user operations impacting throughput and latency.

Branch description