Re: Slowdown with large headings in view

[Ihor Radchenko]

Sebastian Wålinder <s.walinder@gmail.com> writes:

> 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.

This is expected. The problem is with Emacs redisplay engine that cannot
easily handle large number of text properties - on C level.

You can try to set `org-fold-core--optimise-for-huge-buffers' to
'(grab-invisible) locally in the problematic Org file - it should reduce
the number of text properties used at the cost of not preserving folded
drawers when folding the containing heading.

-- 
Ihor Radchenko // yantar92,
Org mode contributor,
Learn more about Org mode at <https://orgmode.org/>.
Support Org development at <https://liberapay.com/org-mode>,
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