GNU bug report logs - #56682
Fix the long lines font locking related slowdowns

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Package: emacs;

Reported by: Gregory Heytings <gregory <at> heytings.org>

Date: Thu, 21 Jul 2022 18:01:01 UTC

Severity: normal

Done: Gregory Heytings <gregory <at> heytings.org>

Bug is archived. No further changes may be made.

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Message #1153 received at 56682 <at> debbugs.gnu.org (full text, mbox):

From: Gregory Heytings <gregory <at> heytings.org>
To: Dmitry Gutov <dgutov <at> yandex.ru>
Cc: 56682 <at> debbugs.gnu.org, Eli Zaretskii <eliz <at> gnu.org>,
 monnier <at> iro.umontreal.ca
Subject: Re: bug#56682: Fix the long lines font locking related slowdowns
Date: Sun, 07 Aug 2022 12:46:47 +0000
[Message part 1 (text/plain, inline)]
>> They aren't, no.  Of course it all depends on where you are in the 
>> file, on your CPU, and so forth.  For me (with locked narrowing 
>> disabled, in dictionary.json, with emacs -Q) M-> takes about 3 seconds.
>
> And it's about 1.5s here.
>

So you're the lucky owner of a fast computer.  And using an optimized 
build.  Not everyone is in that fortunate situation.

>
> Once.
>

No, not once.  It happens every time you modify the buffer and move far 
enough in that buffer.

>> Likewise, if I do for example C-s aan, and then repeat C-s, whenever 
>> the next match is far enough in the buffer I see a delay of about 2 
>> seconds.
>
> Sounds like a performance problem inside isearch. I might take a look.
>

No, isearch is entirely agnostic about font locking.

>> Another test you can do is to lean on C-v after opening the buffer, 
>> you'll see that Emacs becomes very sluggish, sometimes I have to wait 
>> more than 5 seconds to avance from one screenfull.
>
> First of all, these aren't the tests Eli asked for or I performed. Why 
> don't you compare apples to oranges?
>
> Leaning on C-v isn't a scientific test anyway: it compares the speed of 
> two processes internal to Emacs (event handling and rendering), rather 
> than something objective.
>

It's yet another test meant to test Emacs' responsiveness, and it is as 
"objective" as possible: does Emacs choke or does it not?

This bug report was last modified 2 years and 8 days ago.

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