Lethargic rpi3, but seemingly still running

[bob prohaska]

I'm playing with an RPI3 running -current at r349989 and trying to build
a port (firefox) with the ports tree at (....long delay to svnlite info
command.....) 506825 using portmaster under the portmaster-devel script.

The system is still running and mostly idle, as reported by top:

last pid:  8739;  load averages:  0.00,  0.02,  0.00  up 1+12:03:29  20:29:20
36 processes:  1 running, 35 sleeping
CPU:  0.0% user,  0.0% nice,  0.1% system,  0.1% interrupt, 99.8% idle
Mem: 22M Active, 720M Inact, 2324K Laundry, 137M Wired, 57M Buf, 27M Free
Swap: 6349M Total, 23M Used, 6326M Free

  PID USERNAME    THR PRI NICE   SIZE    RES STATE    C   TIME    WCPU COMMAN
 8374 root          1  26    0    27M  9160K biord    1   1:21   0.00% bsdtar
 8739 root          1  21    0    21M  8108K sbwait   3   0:00   0.00% sshd
21314 bob           1  20    0    14M  1120K CPU2     2   3:44   0.20% top
21512 bob           1  21    0    13M  1108K ttyin    1   0:00   0.00% tcsh
  970 root          1  20    0    16M   848K select   0   0:09   0.02% sendma
  957 root          1  21    0    20M   688K select   0   0:05   0.00% sshd
38012 root          1  52    0    15M   656K wait     2   0:58   0.00% bash
  973 smmsp         1  20    0    16M   548K pause    3   0:00   0.00% sendma
 2036 bob           1  20    0    22M   544K select   1   0:22   0.02% sshd
  977 root          1  20    0    12M   412K nanslp   0   0:03   0.00% cron
21511 bob           1  20    0    22M   408K select   0   0:00   0.00% sshd
  826 root          1  20    0    11M   404K select   3   0:03   0.00% syslog
 2001 bob           1  20    0    22M   244K select   1   0:04   0.00% sshd
 2007 root          1  20    0    14M   140K pause    2   0:00   0.00% csh

Every once in a while bsdtar will use a fraction of a percent of cpu, but
that seems to be all that's happening. The timestamp updates every other
second, typing echoes as expected but something like pwd takes twenty
seconds to answer. The controlling terminal for portmaster-devel has been
sitting at

=> SHA256 Checksum OK for rust/2019-05-23/cargo-0.36.0-aarch64-unknown-freebsd.tar.gz.
for about two hours.

There are sporadic reports of
swap_pager: indefinite wait buffer: bufobj: 0, blkno: 516, size: 4096
on the console, but they're sparse. At least according to top there's
no significant swap usage.

This behavior isn't entirely new, but this is the first time it's been
bad enough to seem worth reporting. The filesystem is 74% full, so it's
not out of storage:
Filesystem             1K-blocks     Used    Avail Capacity  Mounted on
/dev/ufs/rootfs        116766684 78989800 28435552    74%    /
devfs                          1        1        0   100%    /dev
/dev/msdosfs/MSDOSBOOT     51096    13552    37544    27%    /boot/msdos

Meanwhile an RPI2 running 11.3-BETA1 #0 r348441 is happily grinding away
on the same problem with ports at 506786. It answered svnlite info /usr/ports
in less than a second.

Thanks for reading, and any thoughts.

bob prohaska