From: Yuan Fu <casouri@gmail.com>
To: Eli Zaretskii <eliz@gnu.org>
Cc: Alan Mackenzie <acm@muc.de>, 59738@debbugs.gnu.org
Subject: bug#59738: c-ts-mode is slow with large buffers.
Date: Wed, 7 Dec 2022 16:40:15 -0800 [thread overview]
Message-ID: <3A956C88-F81D-4DED-B020-178291D405D9@gmail.com> (raw)
In-Reply-To: <83edtb3z6t.fsf@gnu.org>
> On Dec 7, 2022, at 9:23 AM, Eli Zaretskii <eliz@gnu.org> wrote:
>
>> Cc: 59738@debbugs.gnu.org
>> From: Yuan Fu <casouri@gmail.com>
>> Date: Tue, 6 Dec 2022 20:56:13 -0800
>>
>>
>> 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.
>>> [...]
>> Ah, the lovely packet-rrc.c file.
>
> No, this is a different file, dce_12_0_sh_mask.h. It is a header file
> which only has preprocessor #define lines. I'm puzzled why this
> presents such a great difficulty for tree-sitter. Could you take a
> look what happens with that 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.
>
> Right, but with a long series of #define lines there should be no
> parse tree at all…
Ok, I think I know why. At the beginning of the file there is this line
#ifndef _dce_12_0_SH_MASK_HEADER
So it’s parsed into a preproc_ifdef node, which contains every #define directive in the file as its immediate child. Now you have this node with a tons of immediate children. And querying this node in font-lock is very slow, even with a limited range. I think for the query result to be accurate, tree-sitter has to query the whole node without considering the range, then throw away matches that are not in the range.
Anyway, I activated my backup backup plan, which goes down the parse tree to find a sufficiently small node to query. Now scrolling the header file is fast as other files.
Yuan
next prev parent reply other threads:[~2022-12-08 0:40 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
2022-12-07 17:23 ` Eli Zaretskii
2022-12-08 0:40 ` Yuan Fu [this message]
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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