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From: "Mattias Engdegård" <mattiase@acm.org>
To: Olivier Scalbert <olivier.scalbert@algosyn.com>
Cc: Alan Mackenzie <acm@muc.de>, 42490@debbugs.gnu.org
Subject: bug#42490: Emacs is very slow when navigating into a specific C++ file
Date: Fri, 24 Jul 2020 18:46:45 +0200	[thread overview]
Message-ID: <8E02A060-9CF0-4B1F-A780-4F51336291FA@acm.org> (raw)
In-Reply-To: <11f564eb-74f1-980b-53e3-2de64abe62e0@algosyn.com>

Hello Olivier,

Thanks for the report! Could you try Emacs 27 (or git master), building from source if necessary? Those versions should be slightly faster, although the response time is probably well below acceptable.

If we distill the essentials of your file to some sort of benchmark, we might end up with:

(with-temp-buffer
  (c++-mode)
  (dotimes (_ 1000)
    (insert "OP(ed,b0) { ldir(); } /* LDIR */\n"))
  (garbage-collect)
  (let ((t0 (current-time)))
    (font-lock-ensure (point-min) (point-max))
    (time-to-seconds (time-since t0))))

Emacs 26.3 runs it in 11.9 s on this old lappy, but Emacs 27 does it in 3.3 s. This is a clear improvement but we should be able to do better. Alan may have a feeling for where the cycles are spent.






  reply	other threads:[~2020-07-24 16:46 UTC|newest]

Thread overview: 7+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-07-23  7:45 bug#42490: Emacs is very slow when navigating into a specific C++ file Olivier Scalbert
2020-07-24 16:46 ` Mattias Engdegård [this message]
2020-07-24 19:24   ` Alan Mackenzie
2020-07-24 19:34     ` Olivier Scalbert
2020-09-21  9:06       ` Alan Mackenzie
2020-09-21 17:29         ` Olivier Scalbert
2020-09-22 10:03           ` Alan Mackenzie

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