make.conf(5) contains the following statement about MALLOC_PRODUCTION: MALLOC_PRODUCTION (bool) Set this to disable assertions and statistics gathering in malloc(3). It also defaults the A and J runtime options to off. Disabled by default on -CURRENT. I believe the A and J options were from the old malloc implementation (phkmalloc?), while FreeBSD has used jemalloc for many years, which uses a different set of options.