The diff is somewhat clearer with whitespace changes hidden: https://reviews.freebsd.org/D19475?whitespace=ignore-all
Some rough throughput numbers on an amd64 bhyve VM; using `pv </dev/random >/dev/null` for 30 seconds. The VM host was mostly idle. The same build was used for both tests, switching only the tunable:
| Baseline revision | kernel | Stream cipher mode | Throughput (pv) |
| r344844 | GENERIC-NODEBUG | AES-ICM | ~180 MB/s |
| r344844 | GENERIC-NODEBUG | Chacha20 | ~400 MB/s |