Subject: bug#57245: 29.0.50; M-> in a large XML file (without long lines) is slow

From: Stefan Monnier <[email-masked]>
Date: Tue, 16 Aug 2022 16:22:03 -0400

Dmitry Gutov [2022-08-16 22:32:23] wrote:
> On 16.08.2022 19:54, Eli Zaretskii wrote:
>> Stefan, can you see why syntax-related stuff in sgml-mode is so heavy
>> here?
> nxml-syntax-propertize might well be heavier than average, but the delay
> scales linearly with the size of the file.

Indeed, it should be linear.

> Which seems to be exactly the behavior the "font-lock narrowing" was
> supposed to guard from?

Not sure which narrowing you're referring to.
The "locked narrowing" introduced by Gregory is only installed in the
presence of long lines.  It's (currently) not used for large files
(unless they contain long lines, that is).

        Stefan