The populate-volatiles script can be very slow on a read-only rootfs (or any time the cache is disabled). I did some profiling, and 80% of the time is spent validating the volatiles files in the check_requirements function. When there are many volatiles files present, this step can easily consume several seconds.

As a quick proof of concept, I concatenated all of the volatiles files together into a single one before parsing and that significantly improved performance, since check_requirements was only called once.