Okay getting real off-topic now (welcome to HN) but this is not what I expected:

https://github.com/ellie/atuin/issues/952#issuecomment-15378... https://github.com/openzfs/zfs/issues/14290

Apparently when SQLite calls `ftruncate` on the `-shm` file, ZFS will sometimes block for several seconds. Maybe it's waiting for txg timeout? Strange.