Investigate LUKS performance settings
As far as I can tell, homed just uses cryptsetup's default performance settings
However, cryptsetup has some performance tuning options that would be very beneficial depending on the type of storage backing it. For instance, if the home directory is on an SSD, we can almost double our throughput by disabling some queuing in the kernel.
See: https://blog.cloudflare.com/speeding-up-linux-disk-encryption/