freebsd stable - Dec 2020 - Help! 12.2 mem ctrl knob missing, might need 3 times more memory

Hiya,

 after upgrading 11.4 -> 12.2, I get this error:
> sysctl: unknown oid 'vm.pageout_wakeup_thresh' at line 105
How do I adjust the paging now? The ARC is much too small:

Mem: 1929M Active, 109M Inact, 178M Laundry, 1538M Wired, 37M Buf, 88M Free
ARC: 729M Total, 428M MFU, 154M MRU, 196K Anon, 25M Header, 122M Other
     118M Compressed, 533M Uncompressed, 4.52:1 Ratio
Swap: 10G Total, 1672M Used, 8567M Free, 16% Inuse

With 11.4 there was 200M active, 2500M wired, 4200M swap and the ARC
stayed filled to the configured arc_max. And there are not even all
applications loaded yet!

Config: installed 4G ram, application footprint ~11G.

vm.pageout_wakeup_thresh=11000 # default 6886
vm.v_inactive_target=48000 # default 1.5x vm.v_free_target
vfs.zfs.arc_grow_retry=6 # override shrink-event from pageout (every 10sec.)

I did this intentional: the ram is over-used with applications. These
applications are rarely accessed, but should respond to the network. So
they are best accomodated in paging space - taking a few seconds for
page-in at first access does not matter, and not many of them are
accessed at the same time. 

So, I want the machine to page out *before* shrinking the ARC, because
pageout is a normal happening in this layout. The above tuning
achieved exactly that, but now in 12.2 it seems missing.
Without that I would need to install the full 12G RAM, which is just a
waste. 

How do I get this behaviour back with 12.2?