Re: Poor Performance w/ Long Files

[Lennart Borgman]

On Thu, Aug 20, 2009 at 2:09 AM, Pascal J.
Bourguignon<pjb@informatimago.com> wrote:
> Tim Visher <tim.visher@gmail.com> writes:
>
>> Hello Everyone,
>>
>> I work with many large files (+10,000,000 ASCII characters) at work
>> and I've noticed that Emacs does extremely poorly with those files.  I
>> have taken to opening them up in something like Notepad++ to look at
>> them and editing the programs that operate on them in Emacs.  I'd love
>> to be able to just stick with Emacs.
>>
>> Is there something that I just haven't set yet or does Emacs have
>> trouble with large files?
>
> Perhaps you could disable some emacs options that might take time,
> like font-locking.  Basically, if you edit this files in fundamental-mode,
> with truncate-line turned off with C-u 1 M-x toggle-truncate-lines RET and
> with font-locking turned off with C-u -1 M-x font-lock-mode RET,
> it should go faster.


I think we recently got a bug report where the user was using
fundamental-mode to edit a file with very long lines. That was very
slow.

If I remember correctly that depends on how the display engine in
Emacs is organized. It searches for line ends. If I understand Stefan
Monnier correctly this is something that can be cured and have a
rather high priority. So if someone want to jump in and have enough
knowledge to understand this it is probably welcome. (It might be a
difficult problem.)