I noticed some more instances in the system logs of processes being
killed due to lack of swap space. On the most recent and most voluminous
set of killed processes I checked memory usage and it was at 92%. The
CPU graph was mostly flat at 100%. I turned the captive portal off and
CPU usage went down to about 25%. And memory usage is back in the 55% range.
Since I like the software a lot, it looks like I may have to try to run
it on different hardware with higher capacity...