bug#57207: 29.0.50; Fontification is slow after e7b5912b23 (Improvements to long lines handling)

[Eli Zaretskii]

> From: Ihor Radchenko <yantar92@gmail.com>
> Cc: Gregory Heytings <gregory@heytings.org>,  57207@debbugs.gnu.org
> Date: Tue, 16 Aug 2022 20:16:23 +0800
> 
> Throughout my today's attempts to reproduce, I did not see any obvious
> difference in the slowdown between 10000 and 100000 long-line-threshold
> values.

OK, but the slowdown is still pretty much evident, is that right?  Can
you quantify it?  That is, what is the time it takes you to visit the
file, with long-line-threshold set to nil and with it set to its
default value?  Can you time this with the 'time' utility or with
something similar?