Re: RE24 (2.4.15) slapd consuming large amounts of CPU

I upgraded one of our consumers to 2.4.15 recently, from RE24 as of 20090113. Its configuration stayed the same, save for bumping the BDB cache size from 256MB to 2GB. After a few hours of uptime, slapd suddenly begins consuming enormous amounts of CPU (a three- to four-fold increase over less than a few minutes, and is sustained until slapd is restarted). A backtrace (below) shows many threads waiting on a mutex in bdb_cache_*(). This is with BDB 4.7 (with all patches applied) on Debian lenny. 'db_stat -c' output is below (and looks sane), in case that's useful. Thinking thread contention, I bumped the worker thread count (slapd.conf threads directive) down from 32 to 8, which has made no difference.