From: Stefan Monnier via "Bug reports for GNU Emacs, the Swiss army knife of text editors" <bug-gnu-emacs@gnu.org>
To: Eli Zaretskii <eliz@gnu.org>
Cc: 58558@debbugs.gnu.org, Lars Ingebrigtsen <larsi@gnus.org>,
yantar92@posteo.net
Subject: bug#58558: 29.0.50; re-search-forward is slow in some buffers
Date: Sun, 16 Oct 2022 10:23:45 -0400 [thread overview]
Message-ID: <jwvbkqbhnu8.fsf-monnier+emacs@gnu.org> (raw)
In-Reply-To: <83sfjo3tfw.fsf@gnu.org> (Eli Zaretskii's message of "Sun, 16 Oct 2022 14:21:23 +0300")
>> Huh, very odd. Almost as something is... fragmenting in the buffer?
>> We do have many caches and stuff -- perhaps something is... degrading?
>>
>> I guess some C-level perf measurements would be handy here, but that's
>> not something I know much about. Anybody?
>
> AFAIU, we use elaborate caching for regular expressions, so maybe that
> is related. Stefan, any ideas?
The regexp cache hasn't changed between 28 and 29, so that seems
unlikely to be the source of the problem. But that cache is fairly
simple-minded, so it's possible that for some reason it thrashes in
Emacs-29 but not in Emacs-28 (but see below).
IIUC a summary of what we know so far:
- the "yant/re" benchmark is ~20x slower in Emacs-29 than in Emacs-28.
- removing all text properties reduces the factor down to about ~15x.
- that difference is absent after a fresh start: it only appears over time.
Since this benchmark always matches the same regexp, I can't imagine how
the regexp cache could thrash, so it definitely seems to come from
something else.
I'd curious to know the result of the following tests:
- Run the same benchmark twice in a row: does the second run take the
same time as the first, or is the second run significantly faster?
[ if it's faster it might be due to something like the on-the-fly
`syntax-propertize`ation.
BTW, what does the profiler-start/report say?
Is the time 100% spent in `re-search-forward`? ]
- Try to reduce the number of "features" used in the regexp to see how
it affects the slow down. Maybe try a "binary search" where you try
to reduce the regexp to something much simpler and see if some regexps
exhibit the slowdown while others don't?
Stefan
next prev parent reply other threads:[~2022-10-16 14:23 UTC|newest]
Thread overview: 81+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-10-16 1:26 bug#58558: 29.0.50; re-search-forward is slow in some buffers Ihor Radchenko
2022-10-16 9:19 ` Lars Ingebrigtsen
2022-10-16 9:34 ` Ihor Radchenko
2022-10-16 9:37 ` Lars Ingebrigtsen
2022-10-16 10:02 ` Ihor Radchenko
2022-10-16 10:04 ` Lars Ingebrigtsen
2022-10-16 10:53 ` Ihor Radchenko
2022-10-16 11:01 ` Lars Ingebrigtsen
2022-10-16 11:21 ` Eli Zaretskii
2022-10-16 14:23 ` Stefan Monnier via Bug reports for GNU Emacs, the Swiss army knife of text editors [this message]
2022-10-17 0:56 ` Ihor Radchenko
2022-10-18 11:50 ` Lars Ingebrigtsen
2022-10-18 14:58 ` Eli Zaretskii
2022-10-18 18:19 ` Lars Ingebrigtsen
2022-10-18 18:38 ` Eli Zaretskii
2022-12-13 10:28 ` Ihor Radchenko
2022-12-13 13:11 ` Eli Zaretskii
2022-12-13 13:32 ` Ihor Radchenko
2022-12-13 14:28 ` Eli Zaretskii
2022-12-13 15:56 ` Ihor Radchenko
2022-12-13 16:08 ` Eli Zaretskii
2022-12-13 17:43 ` Ihor Radchenko
2022-12-13 17:52 ` Eli Zaretskii
2022-12-13 18:03 ` Ihor Radchenko
2022-12-13 20:02 ` Eli Zaretskii
2022-12-14 11:40 ` Ihor Radchenko
2022-12-14 13:06 ` Eli Zaretskii
2022-12-14 13:23 ` Ihor Radchenko
2022-12-14 13:32 ` Eli Zaretskii
2022-12-14 13:39 ` Ihor Radchenko
2022-12-14 14:12 ` Eli Zaretskii
2022-12-13 18:15 ` Stefan Monnier via Bug reports for GNU Emacs, the Swiss army knife of text editors
2022-12-13 18:40 ` Ihor Radchenko
2022-12-13 19:55 ` Stefan Monnier via Bug reports for GNU Emacs, the Swiss army knife of text editors
2022-12-13 20:21 ` Eli Zaretskii
2022-12-14 11:42 ` Ihor Radchenko
2022-12-13 17:38 ` Stefan Monnier via Bug reports for GNU Emacs, the Swiss army knife of text editors
2022-12-14 12:00 ` Ihor Radchenko
2022-12-14 12:23 ` Ihor Radchenko
2022-12-14 13:10 ` Eli Zaretskii
2022-12-14 13:26 ` Ihor Radchenko
2022-12-14 13:57 ` Eli Zaretskii
2022-12-14 14:01 ` Ihor Radchenko
2023-04-06 11:49 ` Ihor Radchenko
2023-04-06 12:05 ` Eli Zaretskii
2023-04-09 19:54 ` Ihor Radchenko
2023-04-10 4:14 ` Eli Zaretskii
2023-04-10 12:24 ` Ihor Radchenko
2023-04-10 13:40 ` Eli Zaretskii
2023-04-10 14:55 ` Ihor Radchenko
2023-04-10 16:04 ` Eli Zaretskii
2023-04-10 14:27 ` Stefan Monnier via Bug reports for GNU Emacs, the Swiss army knife of text editors
2023-04-11 11:29 ` Ihor Radchenko
2023-04-11 11:51 ` Eli Zaretskii
2023-04-12 13:39 ` Ihor Radchenko
2023-04-12 14:06 ` Stefan Monnier via Bug reports for GNU Emacs, the Swiss army knife of text editors
2023-04-12 14:30 ` Eli Zaretskii
2023-04-12 14:38 ` Stefan Monnier via Bug reports for GNU Emacs, the Swiss army knife of text editors
2023-04-12 15:22 ` Eli Zaretskii
2023-04-12 15:59 ` Alan Mackenzie
2023-04-12 14:38 ` Stephen Berman
2023-04-12 14:42 ` Ihor Radchenko
2023-04-12 14:39 ` Ihor Radchenko
2023-04-12 15:20 ` Stefan Monnier via Bug reports for GNU Emacs, the Swiss army knife of text editors
2023-04-12 23:23 ` Stefan Monnier via Bug reports for GNU Emacs, the Swiss army knife of text editors
2023-04-13 4:33 ` Stefan Monnier via Bug reports for GNU Emacs, the Swiss army knife of text editors
2023-04-13 20:05 ` Ihor Radchenko
2023-04-13 4:52 ` Eli Zaretskii
2023-04-13 5:15 ` Eli Zaretskii
2023-04-12 18:31 ` Alan Mackenzie
2023-04-12 23:25 ` Stefan Monnier via Bug reports for GNU Emacs, the Swiss army knife of text editors
2023-04-13 4:43 ` Stefan Monnier via Bug reports for GNU Emacs, the Swiss army knife of text editors
2023-04-13 12:09 ` Ihor Radchenko
2022-12-13 13:27 ` Stefan Monnier via Bug reports for GNU Emacs, the Swiss army knife of text editors
2022-10-16 10:36 ` Eli Zaretskii
2023-02-19 12:17 ` Dmitry Gutov
2023-02-20 10:24 ` Ihor Radchenko
2023-02-20 14:54 ` Dmitry Gutov
2023-04-10 8:48 ` Mattias Engdegård
2023-04-10 9:57 ` Ihor Radchenko
2023-04-10 10:05 ` Mattias Engdegård
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