emacs-24.1.1 slow scrolling in Fundamental mode with font lock disabled

emacs-24.1.1 slow scrolling in Fundamental mode with font lock disabled

[Maxim Yegorushkin]

I have 9Mb text file with 90000+ lines in it. When opening this file in 
emacs-24.1.1 and scrolling to line 5000 and onwards the scrolling 
becomes very slow and there is a long delay after I press PageDown and 
emacs updates the view.

I heard that font lock may cause this so I disabled font lock in that 
buffer. Disabling font lock doesn't resolve the issue or speed things up 
a bit.

The contents of the file look like this:

2012-10-09 08:35:28.217216000 167.150000  44035
2012-10-09 08:35:28.217216000 167.200000   2859
                                                 2012-10-09 
08:35:28.217216000 167.250000  54888
2012-10-09 08:35:28.233155000 167.150000  66035
                                                 2012-10-09 
08:35:28.233155000 167.250000  44404

(long line wrapped in the above).

I.e. there is a timestamp on each line of it in the form of YYYY-MM-DD 
HH:MM:SS.nnnnnnnnn.

I almost accidentally replaced all 2012-10-09 with YYYY-MM-DD in the 
file and that fixed the issue, the scrolling became swift again.

Do you guys have any clues what may be causing this scrolling slowness 
and why replacing ISO dates with YYYY-MM-DD makes scrolling so much 
faster? (once again I have font lock disabled in that buffer).

-- Maxim

Re: emacs-24.1.1 slow scrolling in Fundamental mode with font lock disabled

[Peter Dyballa]

Am 12.11.2012 um 13:49 schrieb Maxim Yegorushkin:

> Do you guys have any clues what may be causing this scrolling slowness and why replacing ISO dates with YYYY-MM-DD makes scrolling so much faster?

What file type is the file, what is its text encoding, and which modes are active in that buffer?

--
Greetings

  Pete

Real Time, adj.:
	Here and now, as opposed to fake time, which only occurs there and then.

Re: emacs-24.1.1 slow scrolling in Fundamental mode with font lock disabled

[Maxim Yegorushkin]

[-- Attachment #1: Type: text/plain, Size: 557 bytes --]

On 12/11/12 14:33, Peter Dyballa wrote:
>
> Am 12.11.2012 um 13:49 schrieb Maxim Yegorushkin:
>
>> Do you guys have any clues what may be causing this scrolling slowness and why replacing ISO dates with YYYY-MM-DD makes scrolling so much faster?
>
> What file type is the file, what is its text encoding, and which modes are active in that buffer?

I am attaching the archived file. The file has no extension/type, its 
contents are ASCII.

Emacs opens it in Fundamental mode and then I invoke "font-lock-mode" to 
turn off font lock minor mode.

-- Maxim


[-- Attachment #2: q.xz --]
[-- Type: application/x-xz, Size: 465568 bytes --]

Re: emacs-24.1.1 slow scrolling in Fundamental mode with font lock disabled

[Eli Zaretskii]

> From: Maxim Yegorushkin <maxim.yegorushkin@gmail.com>
> Date: Mon, 12 Nov 2012 12:49:51 +0000
> 
> I have 9Mb text file with 90000+ lines in it. When opening this file in 
> emacs-24.1.1 and scrolling to line 5000 and onwards the scrolling 
> becomes very slow and there is a long delay after I press PageDown and 
> emacs updates the view.
> 
> I heard that font lock may cause this so I disabled font lock in that 
> buffer. Disabling font lock doesn't resolve the issue or speed things up 
> a bit.
> 
> The contents of the file look like this:
> 
> 2012-10-09 08:35:28.217216000 167.150000  44035
> 2012-10-09 08:35:28.217216000 167.200000   2859
>                                                  2012-10-09 
> 08:35:28.217216000 167.250000  54888
> 2012-10-09 08:35:28.233155000 167.150000  66035
>                                                  2012-10-09 
> 08:35:28.233155000 167.250000  44404
> 
> (long line wrapped in the above).
> 
> I.e. there is a timestamp on each line of it in the form of YYYY-MM-DD 
> HH:MM:SS.nnnnnnnnn.
> 
> I almost accidentally replaced all 2012-10-09 with YYYY-MM-DD in the 
> file and that fixed the issue, the scrolling became swift again.
> 
> Do you guys have any clues what may be causing this scrolling slowness 
> and why replacing ISO dates with YYYY-MM-DD makes scrolling so much 
> faster? (once again I have font lock disabled in that buffer).

Does scrolling become faster if you type this:

  M-x set-variable RET bidi-paragraph-direction RET left-to-right RET

If it does, then I believe this is an inefficiency in the
bidirectional display engine that is already fixed in the development
sources, and will be part of the upcoming Emacs 24.3 release.  If you
can try the development sources, I think you should see that this
problem is gone.

Re: emacs-24.1.1 slow scrolling in Fundamental mode with font lock disabled

[Maxim Yegorushkin]

On 12/11/12 16:19, Eli Zaretskii wrote:
>> From: Maxim Yegorushkin <maxim.yegorushkin@gmail.com>
>> Date: Mon, 12 Nov 2012 12:49:51 +0000
>>
>> I have 9Mb text file with 90000+ lines in it. When opening this file in
>> emacs-24.1.1 and scrolling to line 5000 and onwards the scrolling
>> becomes very slow and there is a long delay after I press PageDown and
>> emacs updates the view.
>>
>> I heard that font lock may cause this so I disabled font lock in that
>> buffer. Disabling font lock doesn't resolve the issue or speed things up
>> a bit.
>>
>> The contents of the file look like this:
>>
>> 2012-10-09 08:35:28.217216000 167.150000  44035
>> 2012-10-09 08:35:28.217216000 167.200000   2859
>>                                                   2012-10-09
>> 08:35:28.217216000 167.250000  54888
>> 2012-10-09 08:35:28.233155000 167.150000  66035
>>                                                   2012-10-09
>> 08:35:28.233155000 167.250000  44404
>>
>> (long line wrapped in the above).
>>
>> I.e. there is a timestamp on each line of it in the form of YYYY-MM-DD
>> HH:MM:SS.nnnnnnnnn.
>>
>> I almost accidentally replaced all 2012-10-09 with YYYY-MM-DD in the
>> file and that fixed the issue, the scrolling became swift again.
>>
>> Do you guys have any clues what may be causing this scrolling slowness
>> and why replacing ISO dates with YYYY-MM-DD makes scrolling so much
>> faster? (once again I have font lock disabled in that buffer).
>
> Does scrolling become faster if you type this:
>
>    M-x set-variable RET bidi-paragraph-direction RET left-to-right RET
>
> If it does,

It does indeed fixes the problem.

 > then I believe this is an inefficiency in the
> bidirectional display engine that is already fixed in the development
> sources, and will be part of the upcoming Emacs 24.3 release.  If you
> can try the development sources, I think you should see that this
> problem is gone.

Thanks a lot Eli. I will stick this customization in .emacs for now.

-- Maxim

Re: emacs-24.1.1 slow scrolling in Fundamental mode with font lock disabled

[Eli Zaretskii]

> From: Maxim Yegorushkin <maxim.yegorushkin@gmail.com>
> Date: Mon, 12 Nov 2012 16:23:50 +0000
> 
> > Does scrolling become faster if you type this:
> >
> >    M-x set-variable RET bidi-paragraph-direction RET left-to-right RET
> >
> > If it does,
> 
> It does indeed fixes the problem.
> 
>  > then I believe this is an inefficiency in the
> > bidirectional display engine that is already fixed in the development
> > sources, and will be part of the upcoming Emacs 24.3 release.  If you
> > can try the development sources, I think you should see that this
> > problem is gone.
> 
> Thanks a lot Eli. I will stick this customization in .emacs for now.

If you never expect to have to display bidirectional scripts, like
Arabic, you can make that the default:

  (setq-default bidi-paragraph-direction 'left-to-right)