Slapd tuning:
"threads": This directive sets the number of threads that slapd uses to
process requests. What this value should be I've generally found to be a
function of the number of "real" cores on the system. I.e., on a 2 CPU box
with one core each, I set this to 8, or 4 threads per real core. This is a
"read" maximized value. The more threads that are configured per core, the
slower slapd responds for "read" operations. On the flip side, it appears
to handle write operations faster in a heavy write/low read scenario.