I ask because the command "sysctl -w kstat.spl.misc.spl_misc.simulate_pressure=<amount of ram to release in bytes>" no longer seems to work:
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$ sysctl -w kstat.spl.misc.spl_misc.simulate_pressure=4294967296
sysctl: unknown oid 'kstat.spl.misc.spl_misc.simulate_pressure'
There's also no /etc/zfs/zsysctl.conf or example file created by default (is there supposed to be?), I've created one myself so I can set kstat.zfs.darwin.tunable.zfs_arc_max in it, but it's going to be a while before my next restart (got a tonne of data to copy into a new ZFS dataset and I'd prefer to just let it run).
Until now I haven't bothered touching the ARC settings, but the size seems to grow a lot faster when you have multiple proper ZFS datasets; until recently I've only really been using a single zvol which never caused the ARC to grow very much despite its size, but with me copying terabytes of data into a new plain dataset I've seen ARC usage shoot up and while it does back off with high memory pressure as expected, there is still some noticeable impact on system performance so I'd like to limit it to 4gb or so till I can install more RAM.