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

From: Ihor Radchenko <[email-masked]>
Date: Mon, 30 May 2022 23:01:07 +0800

Chen Bin <[email-masked]> writes:

> Run below code in both Emacs 28.1 and Emacs 27.1
>
> ;; Run "base64 /dev/urandom | head -c 3000000000 > 3g.txt" to create 3g.txt
> ;; Then run below code in Emacs,
>
> Using same machine, same emacs setup, 28 is alwasy much slower than 27.

On my system:

Emacs-27          (0.032783519 0 0.0) vs (0.093436952 0 0.0)
Emacs-28 (latest) (0.037079772999999996 0 0.0) vs (0.162106006 0 0.0)
Emacs-29 (latest) (0.03358834 0 0.0) vs (0.15387368299999998 0 0.0)

Best,
Ihor