Subject: bug#15876: 24.3.50; Highly degraded performance between rev 114715 and 115006

From: Stefan Monnier <[email-masked]>
Date: Tue, 19 Nov 2013 20:47:52 -0500

> --8<---------------cut here---------------start------------->8---
> ;; highlight trailing whitespaces in all modes
> (setq-default show-trailing-whitespace t)
> --8<---------------cut here---------------end--------------->8---

Can you try to compare the performance of revision 114849 and
revision 114848?  The difference between the two is that the region
highlighting was moved from C to Elisp.  This usually shouldn't affect
performance, but maybe there's some interaction with redisplay
that ends up disabling most optimizations?

        Stefan