Too many pythons in poudriere

In trying to compile www/chromium under poudriere on a Pi3 there
comes a point when five python2.7 sessions totaling more than 2 GB
in size are running at once. Obviously, swap is swamped and the Pi3
is running at a crawl. It hasn't givem up, however.

Poudriere was started with -J 2 and make is limited to 2 jobs. 
Is there an analogous limit to how many pythons are loosed at
once? It looks like there's only one builder, so it isn't
obvious that -J 1 would help; I'll try it if this job stops
prematurely. Progress, such as it is, can be seen at
http://www.zefox.org/~bob/poudriere/data/logs/bulk/main-default/2021-07-05_14h06m26s/build.html

The last time www/chromium was compiled (using make) on this machine 
I don't remember seeing such a python jam. If it happened at all the 
Pi3 worked through it faster than presently. 

Thanks for reading,

bob prohaska