bug#24565: 25.1: info freezes on some elements

[Eli Zaretskii]

> From: Nikolay Kudryavtsev <nikolay.kudryavtsev@gmail.com>
> Cc: 24565@debbugs.gnu.org
> Date: Fri, 30 Sep 2016 13:50:39 +0300
> 
> Here's a profiler-report structure from test 1:
> - command-execute 3664  95%
>   - call-interactively 3664  95%
>    - funcall-interactively 3615  94%
>     - next-line 3614  94%
>      - line-move 3614  94%
>         line-move-visual 2054  53%
>       - line-move-partial 517  13%

If line-move-visual takes the lion's share of the time, then I think
the call to font-info in default-font-height is the prime suspect.  It
happened before: some fonts make that call very expensive, for some
reason.  We did introduce an optimization to alleviate that, but only
when the font in question is the default face's font, which is not
your case.

If my suspicion turns out to be correct, I think the only workaround
(if this problem is annoying enough) is to customize your font setup
to use some other font for these symbols.