From: Yuan Fu <casouri@gmail.com>
To: Alan Mackenzie <acm@muc.de>
Cc: 59738@debbugs.gnu.org
Subject: bug#59738: c-ts-mode is slow with large buffers.
Date: Tue, 6 Dec 2022 20:56:13 -0800 [thread overview]
Message-ID: <87E351E0-2EE2-434A-9609-86506D2F263D@gmail.com> (raw)
In-Reply-To: <Y4iU7VdA/GkvRfxG@ACM>
Alan Mackenzie <acm@muc.de> writes:
> Hello, Emacs.
>
> In an up to date (2022-11-30) master started as $ emacs --no-desktop:
>
> The file .../drivers/gpu/drm/amd/include/asic_reg/dce/dce_12_0_sh_mask.h
> in the Linux source tree is 6.8 MB big, consisting of a large number of
> #defines and comments, but nothing else.
>
> To scroll through it in c-ts-mode takes a little over 26 minutes on my
> system. By comparison, in C Mode it takes 31 seconds. There would
> appear to be a need for some optimisation in c-ts-mode, here.
>
>
> The file
> https://gitlab.com/wireshark/wireshark/-/raw/master/epan/dissectors/packet-rrc.c
> (see bug #45248) (10 MB) takes 578 seconds to scroll in c-ts-mode. It
> scrolls through the first 83% of the buffer rapidly, then chokes on a big
> brace block initialisation. Also, the font-locking fails part way
> through this brace block (without any apparent speed up).
>
> For comparison, the scrolling takes 30 seconds in C Mode. There seems to
> be a need for optimisation of c-ts-mode in this case, too.
>
>
> For completeness, I used M-: (time-scroll) in the following for the
> timings:
>
> (defmacro time-it (&rest forms)
> "Time the running of a sequence of forms using `float-time'.
> Call like this: \"M-: (time-it (foo ...) (bar ...) ...)\"."
> `(let ((start (float-time)))
> ,@forms
> (- (float-time) start)))
>
> (defun time-scroll (&optional arg)
> (interactive "P")
> (message "%s"
> (time-it
> (condition-case nil
> (while t
> (if arg (scroll-down) (scroll-up))
> (sit-for 0))
> (error nil)))))
Ah, the lovely packet-rrc.c file. We had some discussion of it in
bug#59415, basically it contains some syntax that screws tree-sitter up.
The block initialization you see makes tree-sitter into erroneously
generating a very tall tree: it recognizes all the opening bracket and
ignores (almost) all the closing brackets. That causes operations on the
tree to be much much slower than it normally is.
I added some fix so the rest of the file can be largely unaffected, and
reported this problem to tree-sitter-c’s developer (no reply as of now).
There is not much we can do to fix this, and since it’s rare, I think a
user could probably just use c-mode for this kind of files.
Yuan
next prev parent reply other threads:[~2022-12-07 4:56 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-12-01 11:50 bug#59738: c-ts-mode is slow with large buffers Alan Mackenzie
2022-12-03 10:37 ` Yuan Fu via Bug reports for GNU Emacs, the Swiss army knife of text editors
2022-12-07 4:56 ` Yuan Fu [this message]
2022-12-07 17:23 ` Eli Zaretskii
2022-12-08 0:40 ` Yuan Fu
2022-12-08 20:37 ` Eli Zaretskii
2022-12-10 21:34 ` Alan Mackenzie
2022-12-10 23:14 ` Yuan Fu
2022-12-11 7:25 ` Eli Zaretskii
2022-12-11 13:22 ` Alan Mackenzie
2022-12-11 16:38 ` Dmitry Gutov
2022-12-11 6:45 ` Eli Zaretskii
2022-12-11 17:13 ` Alan Mackenzie
2022-12-11 17:38 ` Eli Zaretskii
2022-12-11 18:39 ` Alan Mackenzie
2022-12-11 19:14 ` Eli Zaretskii
2022-12-13 1:20 ` Stefan Kangas
2022-12-07 14:34 ` Eli Zaretskii
2022-12-07 14:58 ` Eli Zaretskii
2022-12-07 15:46 ` Alan Mackenzie
2023-01-07 23:08 ` Yuan Fu
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