bug#16875: python, comint-mode: Large output makes Emacs freeze

[Eli Zaretskii <eliz@gnu.org>]

> From: fgallina@gnu.org (Fabián Ezequiel Gallina)
> Cc: 16875@debbugs.gnu.org,  andreas.roehler@easy-emacs.de
> Date: Mon, 28 Jul 2014 18:35:09 -0300
> 
> Eli Zaretskii <eliz@gnu.org> writes:
> 
> >> From: fgallina@gnu.org (Fabián Ezequiel Gallina)
> >> Date: Sat, 26 Jul 2014 23:22:41 -0300
> >> 
> >> 
> >> Emacs is still slow, but at least responds to commands.  I feel that
> >> everything that could be optimized on the comint side is pretty much
> >> there and that the slowness being experienced is in fact related to the
> >> long-lines slowness bug mentioned before[0].
> >
> > That bug is about displaying long lines.  Is the code that is slow
> > involved in displaying such lines?  If there's no display involved,
> > then the discussion you point to is not relevant.
> >
> > Also, please tell how long are your lines, on the average.
> >
> 
> Yes, such code outputs a long line consisting of 841601 chars.

In that case, yes, that's the "long line display slowness" problem.
If you profile Emacs with 'profiler-start' and 'profiler-report', you
should see that most of the time is spent in redisplay.

> Operations seem to take longer and longer as point moves away from the
> beginning of buffer.

That's expected, although the time should level out after some number
of lines.