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

Previous Next

Full log

Message #526 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>,
 Stefan Monnier <monnier <at> iro.umontreal.ca>
Subject: Re: bug#56682: Fix the long lines font locking related slowdowns
Date: Mon, 01 Aug 2022 09:56:11 +0000

[Message part 1 (text/plain, inline)]

>> Given your and Dmitry's feedback, I just tried to add an explicit call 
>> to (syntax-ppss (point-max)), without narrowing, when the buffer is 
>> opened (see below).
>> 
>> The problem is that this is, as I said, slow.  On my laptop, opening a 
>> 1 GB file takes about 6 seconds.  The call to syntax-ppss adds 70 
>> seconds, so opening a large file becomes an order of magnitude slower 
>> (13 times slower).  Which I think is too much for the added benefit.
>
> But that only has to happen when the buffer is scrolled to the bottom, 
> right?
>

No, it happens when the buffer is opened.  Given the importance that you 
and Stefan seem to give to that function, it is, with the patch I sent in 
my previous post, called once on the whole buffer (without any narrowing) 
when the file is opened.  Later calls (inside fontification-functions or 
post-command-hook) are subject to a forced narrowing.

>
> And syntax-ppss's speed depends on the rules applied by the particular 
> major mode. Those could be sped up. Some optimization of this function's 
> speed is not out of the question either.
>

They would be more than welcome.  In fact, without such optimizations, it 
would be unreasonable to do what the patch does.

Previous Next

GNU bug tracking system
Copyright (C) 1999 Darren O. Benham, 1997,2003 nCipher Corporation Ltd, 1994-97 Ian Jackson.