Multi-thread read performance

[olsonanl]

I've been experimenting with NuDB and ran into the following issue - I would like to have multiple worker threads access the database concurrently, entirely read-only. There seems to be a bottleneck where I only get 2-3x speedups; intel profiler showed what looks to be locking overhead. Should I be able to see higher concurrency for this? Or perhaps am I seeing I/O read rate issues (the data file is in /dev/shm ramdisk for this testing)

Thanks, Bob