Re: Emacs awfully slow on some files

[Fabian Ezequiel Gallina <galli.87@gmail.com>]

2009/8/11 Stefan Monnier <monnier@iro.umontreal.ca>:
>> I have a file which is 1 MB long and all of the content is on a single
>> line.  Using Emacs on this file is pretty much impossible due to the
>> super-sluggish behavior.  It's embarrassing.  Why is this?
>
> It's probably a combination of various pieces of code which make
> incorrect assumptions about the expected line length.
>
>> Can it be fixed?
>
> Yes.
>
>

Where should I start looking at in order to try fix this. I really
would like to be able to use Emacs on ugly files too.

>> This is with fundamental-mode, by the way.
>
> Good: in several other modes, I could argue that such a long line is
> a bug, but fundamental-mode should cater to weird files.
>

Actually today I was editing to an SQL file which had really long
lines and was slow as hell, there are several modes that should
support very long lines without making Emacs that slow not only
fundamental-mode.

I guess this should be a priority thing to fix, I'll try to see if I
can find some solution, unfortunately my C knowledge is not that good
and I'm new to Emacs Lisp but I will give it a try and let you know if
I can do some enhancement.

>
>> `forward-char' and `backward-char' are pretty much the only usable
>> commands, even "C-h f" (describe-function) is extremely slow in
>> this scenario.
>
> Please report a bug for it via M-x report-emacs-bug, and ideally include
> some recipe (in case it depends on the actual content of the long line,
> for example, or if it needs more than "emacs -Q" to reproduce).
>
>
>        Stefan
>



Best Regards,
-- 
Fabián E. Gallina