GNU bug report logs - #58558
29.0.50; re-search-forward is slow in some buffers

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From: Lars Ingebrigtsen <larsi <at> gnus.org>
To: Ihor Radchenko <yantar92 <at> posteo.net>
Cc: 58558 <at> debbugs.gnu.org, Eli Zaretskii <eliz <at> gnu.org>, Stefan Monnier <monnier <at> iro.umontreal.ca>
Subject: bug#58558: 29.0.50; re-search-forward is slow in some buffers
Date: Tue, 18 Oct 2022 13:50:02 +0200

Ihor Radchenko <yantar92 <at> posteo.net> writes:

> After 11 hours of Emacs uptime and some edits in the buffer (actually,
> just a few hours; mostly idle), running the benchmark-progn
> repetitively:
>
> ;; Elapsed time: 8.339753s
> ;; Elapsed time: 9.243140s
> ;; Elapsed time: 9.868761s
> ;; Elapsed time: 10.330362s
> ;; Elapsed time: 11.279218s
> ;; Elapsed time: 13.581893s
> ;; Elapsed time: 13.675609s
> ;; Elapsed time: 14.553157s
> ;; Elapsed time: 14.651782s
> ;; Elapsed time: 17.253983s
>
> The elapsed time gradually increases. It is definitely a clue, but very
> odd one.

The slowdowns are so dramatic that they should show up on a profiler --
which might give us a clue which parts of Emacs is slowing down.  I
briefly tried to use "perf" under Linux to connect to a running Emacs
and get some data out of it, but...  er...  I've never used it before,
and...

Does anybody have a recipe for how to do runtime function tracing for a
running process?

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