Subject: bug#55729: 27.1; Emacs 28.1 `string-match' is five times slower than Emacs 27.1

From: Eli Zaretskii <[email-masked]>
Date: Mon, 30 May 2022 18:58:17 +0300

> Resent-From: Lars Ingebrigtsen <[email-masked]>
> Original-Sender: "Debbugs-submit" <[email-masked]>
> Resent-CC: [email-masked]
> Resent-Sender: [email-masked]
> Cc: [email-masked]
> From: Lars Ingebrigtsen <[email-masked]>
> Date: Mon, 30 May 2022 17:09:58 +0200
> 
> Chen Bin <[email-masked]> writes:
> 
> > Using same machine, same emacs setup, 28 is alwasy much slower than 27.
> 
> How much slower?
> 
> I tried your test, and the results were within a few percentages of each
> other in 27.1 and 28.1.

With a 3GB file being inserted non-literally, there could be factors
at work here that are entirely unrelated to processing speed.  The
implementation of string-match basically didn't change between Emacs
27 and Emacs 28, AFAICT.