bug#48871: 27.2; Unusably slow in C# mode

[jan]

Hi Eli,
had already tried the -Q option. Emacs started but when I tried "M-x
csharp-mode" it didn't recognise it. I tried exactly the same on the
normally-started emacs to check I was entering it correctly and that
did understand it.
I guess the -Q effectively disables some modes? I was surprised.

Yep, customisation may well  be the issue here.

I have a file of equivalent size which should demo the issue but can't
zip it as gmail blocks anything with a zip attached, I can post as
attachment directly but it's 220KBytes, you ok with that on your
mailing list?

cheers

jan


On 06/06/2021, Eli Zaretskii <eliz@gnu.org> wrote:
>> Date: Sun, 6 Jun 2021 13:32:09 +0100
>> From:  jan via "Bug reports for GNU Emacs,
>>  the Swiss army knife of text editors" <bug-gnu-emacs@gnu.org>
>>
>> C# mode is slow beyond to the point of being completely unusable. This
>> seems to have started when I upgraded from emacs 26 to emacs 27.2. The
>> file is ~220K. At the start of the file, typing takes 3 or 4 secs *per
>> character* to appear (at the end of the file, instantaneous). It's
>> forcing me to use visual studio to do all simple text editing and I
>> don't like that.
>> [...]
>> Turns out emacs has a profiler, thought I'd try it.
>
> Good start, thanks.
>
>> Not sure what to do.
>
> Post an example of a file where typing lags by several seconds, and
> let's see what people here can tell about that.
>
> But before that, start "emacs -Q", visit the C# file that gave you
> such trouble, and try typing there.  If the lag disappears, then look
> for some of your customizations that could explain the slow responses.
>