RPI3 swap experiments (insufficient swap)

[bob prohaska]

Just for fun, and to provide an alternate view of OOMA behavior on an RPI3,
a j4 buildworld was again run with deliberately insufficient swap.  A single 
1 GB partition was used, on the microSD card. Having sufficient swap on microSD 
allows a successful -j4 buildworld.

The debris I could collect is on display at
http://www.zefox.net/~fbsd/rpi3/swaptests/r336877M/1gbsdflash/


The behavior suggests that OOMA misbehaves in both possible directions: It kills
processes when it shouldn't, and does _not_ kill them when it should. The same
behavior was observed some weeks ago, but this time it's possible to watch the 
gstat output.

Please note that the messages
Aug  1 18:08:13 www kernel: v_free_count: 5439, v_inactive_count: 1
Aug  1 18:08:25 www kernel: pid 93301 (c++), uid 0, was killed: out of swap space
are stale, left over from an earlier run with swap on USB flash.

There are a couple of core files included in the exhibit. At least the top session
crashed with a signal 11, it happened when I was watching and I restarted top, which
then ran normally until I left the console.  That's a somewhat unusual occurrence, 
signal 11's haven't been seen on this box any time recently. I did not see what 
happened to tcsh, but it left one core file. 

In the end the console carried a stream of what look like hardware errors referencing
da0, but all was forgiven after reboot and a couple cycles of fsck -fy. An excerpt
is in the readme file.

One curiosity is that the system remained responsive to ping. The console wasn't
responsive, ssh sessions either disconnected or froze. Power-cycling was the only
way to reboot. 

Thanks for reading, I hope the observations are of some use.

bob prohaska