It looks like it’s the number of distinct terms in each taxonomy that does it. I can render 25,000 regular pages in a minute or so, but once I added a few randomly-generated taxonomies with around a thousand terms each, Hugo was using 6GB of RAM and pounding on three cores for 23 minutes.
For your amusement, here’s what it looked like when it finished:
% time hugo
Started building sites ...
Built site for language en:
0 of 2 drafts rendered
0 future content
0 expired content
25298 regular pages created
14788 other pages created
4 non-page files copied
516634 paginator pages created
10 rushed created
10 gruel created
10 unfattable created
10 agglomerator created
17 wordplay created
1200 unqualifiedness created
10 pneumological created
10 assentatious created
10 kerogen created
10 trichinous created
10 philosophism created
10 bemist created
8 pecunious created
10 biconcave created
10 vulsinite created
1200 conspiratress created
10 paraaminobenzoic created
43 categories created
10 hydrachnid created
5 antrophore created
1200 unfreely created
10 archdepredator created
10 semirare created
1200 postwoman created
10 clovene created
6 series created
10 nonbilabiate created
10 urohematin created
659 tags created
10 diosmotic created
800 tenderness created
800 cothy created
total in 1365380 ms
real 22m48.707s
user 70m49.571s
sys 3m18.912s
(yes, it created 559,269 files in public
; thank goodness for SSDs!)
-j