Re: UVM behavior under memory pressure

[Mouse <mouse%Rodents-Montreal.ORG@localhost>]

> 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:

> 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

> Shouldn't UVM choose, in this case, to reclaim pages from the file
> cache for the process data ?

It strikes me as possible, at least, that it *is* doing that, only to
have more file data push them out again - essentially, that process
pages and file-cache pages are thrashing against one another.  Do you
have any particular reason to think it isn't?  I do note that your CPU
states (which I cut, above) show over 95% system time, which is one of
the things I would expect if that's what's happening.

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