Slowdown with large headings in view

["Sebastian Wålinder" <s.walinder@gmail.com>]

Hello!

I have massive org-mode file with thousands of SRC blocks.

As the file grew, I started to get very poor performance, but setting `org-fold-core--ignore-modifications` to `t` solved it.

However, I still get very poor performance when a lot of folded headings are in view. It gets slower as headings with more text hidden inside its fold come into view.

I have tried running the profiler to find out what the issue is, but no matter how laggy Emacs gets, the profiler records practically no CPU samples or memory usage.

When the massive org buffer is in view and showing large folded headlines, any command run is very slow, even if the action is performed in another buffer entirely. It returns to normal when no window is showing the headings, as well as when I bring the folded headings out of view or unfold them.

I tried disabling font-lock, but it didn't do anything.

How can I profile this, or does anyone have a guess of what could be causing it?

Thank you!
Sebastian