Also thanks to @raykholo for pointing out to me out of band that my instructions for disabling transparent huge pages were quietly wrong.
Anyone tracking this, please use this instead:
echo 'w /sys/kernel/mm/transparent_hugepage/enabled - - - - never
w /sys/kernel/mm/transparent_hugepage/defrag - - - - never' > /etc/tmpfiles.d/thp.conf
systemd-tmpfiles --create
These are not configurable via sysctl, and if you have previously created /etc/sysctl.d/10-huge-pages.conf following my earlier instructions, you can delete it.
I didn’t validate that correctly when I wrote it, and I’ve failed to notice ever since that it was not working correctly. Nice catch, and thank you!