UVM behavior under memory pressure

[Manuel Bouyer <bouyer%antioche.eu.org@localhost>]

hello
on a system running netbsd-9 from mid-august, I ended up in a state where
the system has little free memory, no free swap and almost 40% of RAM used
by the file cache:

load averages:  9.00,  5.02,  2.86;               up 0+11:30:56        20:57:39
97 processes: 2 runnable, 91 sleeping, 1 stopped, 3 on CPU
CPU states:  0.7% user,  0.0% nice, 96.5% system,  0.0% interrupt,  2.6% idle
Memory: 4987M Act, 2436M Inact, 123M Wired, 198M Exec, 2918M File, 4216K Free
Swap: 520M Total, 520M Used, 4K Free

  PID USERNAME PRI NICE   SIZE   RES STATE      TIME   WCPU    CPU COMMAND
    0 root       0    0     0K   30M CPU/3     11:27  0.00%   122% [system]
 1009 bouyer    43    0  2978M  275M parked/0   9:32 27.78% 27.78% firefox68
 1519 bouyer    26    0  2583M  141M RUN/0      0:37 20.90% 20.90% firefox68
 1243 bouyer    25    0  2912M  350M RUN/2      2:56 60.96% 20.12% firefox68
 7341 bouyer    26    0  3221M 2807M CPU/2      5:07 17.09% 17.09% openscad
  729 bouyer    76    0   202M   39M select/3  26:03 16.65% 16.65% X

Of course the system is very slow 
Shouldn't UVM choose, in this case, to reclaim pages from the file cache
for the process data ?
I'm using the default vm.* sysctl values.

-- 
Manuel Bouyer <bouyer%antioche.eu.org@localhost>
     NetBSD: 26 ans d'experience feront toujours la difference
--