Re: emacs takes exhorbitantly long to read long, one-line files.

[Eli Zaretskii]

> From: Karl Fogel <address@hidden>
> Date: Mon, 20 May 2013 09:32:23 -0500
> Cc: Dmitry Antipov <address@hidden>
> 
> Dmitry Antipov <address@hidden> writes:
> >> I already had that in my init.el. I've also tried creating an empty
> >> file and setting it to fundamental-mode. In both these cases the
> >> behavior is the same.
> >
> >Hm...is it the same with emacs -Q?
> >
> >> I did notice that emacs is faster - but still unusably slow - when
> >> toggle-truncate-lines is true.
> >
> >Try (setq-default cache-long-line-scans t) too.
> 
> That should help a lot.

But it won't succeed to make Emacs usable with such files.  E.g., try
this:

  M->
  C-p

and count the seconds it takes to perform the second command.

What Emacs does behind the scenes is go to the beginning of the
previous _physical_ line (which is quite fast in this case), and the
go all the way down the humongously long line, one character at a
time, until it finds the place to put the cursor.  Unless we make
radical changes in this algorithm, how can anyone expect reasonable
performance from this?