dmcrypt-backed filesystems use encryption from the moment they are open by the device-mapper initscript. Because of that, they could benefit from "use entropy" in the initscript's depend(). "Entropy" is provided by RNG control daemons such as rng-tools. Reproducible: Always
If you need that extra entropy, you can add rc_use=entropy in your own /etc/conf.d/device-mapper config, per rc.conf.