We are running almost the same setup, except that we are using back-bdb.
We are not seeing this behaviour, although our performance testing from
OpenLDAP-2.1.8 is is showing only about 7 queries/sec answered (we need a
minimum of 20 queries/sec throughput). We have also found that anytime
we do load testing, slapd dies after a few hours, so I wouldn't label
OpenLDAP-2.1.8 as being production ready. This is on 3 CPU machines
with 3 GB of memory. We have a back-bdb cache of 1GB. Our CPU load did
not increase appreciably during load testing (0.01 load).
Our database is very small, just about 7500 entries or so. Originaly I
used ldbm but bdb is slower. I didn't manage to run the multiple CPU tests
by now but a slowdown even with async settings on isn't what I expected.
Are you using Solaris 9?