Subject: bug#38407: 27.0.50; infinite loop with display of large file without newlines

From: Phil Sainty <[email-masked]>
Date: Thu, 28 Nov 2019 13:30:12 +1300

On 2019-11-28 10:52, Pieter van Oostrum wrote:
> I used a 100KB json file from my Firefox profile
> (but loaded as a text file)

I missed that bit, so I should add that global-so-long-mode doesn't
care about text-mode by default.  It mostly targets programming modes
(.json filenames included), but you can customize so-long-target-modes
to include text-mode if you think you're likely to encounter such
files in text-mode in practice.

However I wouldn't expect a 100K file in text-mode to cause anything
remotely like the degree of performance issue you've encountered.  I
have a 256K single-line .txt file which suffers perceivable slow-downs
at the end of the file (in text-mode with visual-line-mode enabled),
but nothing remotely so catastrophic as you're reporting.  On my
machine, I'd estimate less than a half-second delay when scrolling,
so the difference is several orders of magnitude.

Are you seeing that starting from "emacs -Q" ?

-Phil