PQ_LAUNDRY: unexpected behaviour

Hi all,

I'm seeing some unexpected PQ_LAUNDRY behaviour on something fairly close
to -CURRENT (drm-next-4.7 with an IFC on 26 Dec). Aside from the use of
not-quite-CURRENT, it's also very possible that I don't understand how the
laundry queue is supposed to work. Nonetheless, I thought I'd check whether
there is a tunable I should change, an issue with the laundry queue itself,
etc.

After running X overnight (i915 can now run overnight on drm-next-4.7!), I
end up with a little over half of my system memory in the laundry queue and
a bunch of swap utilization. Even after closing X and shutting down lots of
services, I see the following in top:

```
Mem: 977M Active, 31M Inact, 4722M Laundry, 1917M Wired, 165M Free
ARC: 697M Total, 67M MFU, 278M MRU, 27K Anon, 22M Header, 331M Other
Swap: 4096M Total, 2037M Used, 2059M Free, 49% Inuse

  PID USERNAME    THR PRI NICE   SIZE    RES STATE   C   TIME    WCPU
COMMAND
  911 root          1  52    0 57788K  4308K select  1   0:00   0.00% sshd
  974 root          1  20    0 43780K     0K wait    2   0:00   0.00%
<login>
 1406 jon           1  20    0 33520K  2748K select  0   0:04   0.00%
gpg-agent
 2038 jon           1  20    0 31280K  5452K ttyin   3   0:18   0.00% zsh
 1251 jon           1  22    0 31280K  4500K pause   3   0:02   1.46% zsh
 7102 jon           1  20    0 31280K  3744K ttyin   0   0:00   0.00% zsh
 1898 jon           1  20    0 31280K  3036K ttyin   1   0:00   0.00% zsh
 1627 jon           1  21    0 31280K     0K pause   0   0:00   0.00% <zsh>
22989 jon           1  20    0 31152K  6020K ttyin   1   0:01   0.00% zsh
22495 jon           1  49    0 31152K  6016K ttyin   0   0:02   0.00% zsh
 1621 jon           1  20    0 28196K  8816K select  2   0:40   0.00% tmux
 6214 jon           1  52    0 27008K  2872K ttyin   1   0:00   0.00% zsh
 6969 jon           1  52    0 27008K  2872K ttyin   3   0:00   0.00% zsh
 6609 root          1  20    0 20688K  4604K select  1   0:00   0.00%
wpa_supplicant
  914 root          1  20    0 20664K  5232K select  2   0:02   0.00%
sendmail
  917 smmsp         1  20    0 20664K     0K pause   0   0:00   0.00%
<sendmail>
24206 jon           1  23    0 20168K  3500K CPU0    0   0:00   0.00% top
  921 root          1  20    0 12616K   608K nanslp  1   0:00   0.00% cron
```

Are there any things I could do (e.g., sysctls, tunables) to figure out
what's happening? Can I manually force the laundry to be done? `swapoff -a`
fails due to a lack of memory.

Thanks,


Jon
-- 
jonathan_at_FreeBSD.org