Slow documentation build

[nijel]

I've recently switched translate-toolkit documentation to furo (in translate/translate#5338).

What I didn't notice when doing the change is that the documentation build time went from ~1 minute to ~5 minutes just because of changing the theme. Is something like this expected? What would be the best approach to find what causes the slowdown?

[nineteendo]

The sidebar maybe? Furo is intended for smaller documentation sets.

[nijel]

I've tried removing some documents from toctree and that doesn't seem to have any visible impact. Completely disabling toctree rendering makes the difference, though (I've modified _compute_navigation_tree to not call toctree at all).

PS: I'm using Furo for Weblate documentation for years and it builds in ~30 seconds while it is not really small (contains 152 rst documents, translate-toolkit has 259).