RPI3 swap experiments ["was killed: out of swap space" with: "v_free_count: 5439, v_inactive_count: 1"]

[bob prohaska]

Simply moving all swap to microSD (and leaving vm.pageout_oom_seq at the
default value of 12) allowed an uneventul -j4 buildworld on r337226M,
upgrading to r337564M with the patches suggested to date still in place.
There were no warnings or errors on the console or controlling terminal.

The microSD card used for /root, /tmp and swap is a Sandisk Ultra, supposedly
a notch or two slower than the Sandisk Extreme USB flash drive that caused
all the trouble.

One small curiosity happened on reboot: the old kernel reported in part:
Syncing disks, buffers remaining... 8 8 8 8 8 8 8 8 (da0:umass-sim0:0:0:0): WRITE(10). CDB: 2a 00 07 20 e6 00 00 00 40 00 
(da0:umass-sim0:0:0:0): CAM status: CCB request completed with an error
(da0:umass-sim0:0:0:0): Retrying command, 3 more tries remain
8 8 8 8 8 8 8 8 8 8 8 8 
Giving up on 8 buffers
Uptime: 1d4h36m2s

There followed a repetition of previously-seen errors on da0, but somewhow u-boot
got control and the system came back up after self-fsck without intervention.

Do the errors reported above narrow down at all what might be going wrong? Is there
a patch or setting that would reveal what the CCB request error was?
 

More complete transcripts are at
http://www.zefox.net/~fbsd/rpi3/swaptests/r337226M/3gbsdflash/

Thanks for reading!

bob prohaska