GNU bug report logs -
#16875
python, comint-mode: Large output makes Emacs freeze
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Message #20 received at 16875 <at> debbugs.gnu.org (full text, mbox):
Andreas Röhler <andreas.roehler <at> easy-emacs.de> writes:
>> Indeed, "pprint" should solve it already. Maybe make that the default?
>> IMO looks better anyway.
That's changing the Python shell default behavior and I that's out of
the scope of python.el.
Stefan Monnier <monnier <at> iro.umontreal.ca> writes:
>>> http://debbugs.gnu.org/cgi/bugreport.cgi?bug=13675
>> To a certain extend.
>> There some more operations done by comint, which aren't needed when
>> executing Python code from source but may slow down it.
>
> I expect the main slowdown comes from font-lock. But indeed, it''d be
> good to try and profile it to see where the time is spent.
>
From profiling, a lot of time spent on font-locking while another bunch
is spent at `comint-postoutput-scroll-to-bottom' (default member of
`comint-output-filter-functions').
After disabling both, the output is sent pretty quickly and Emacs, while
it's a bit slower, it's still responsive.
WRT the font-lock slowness I must say I'm not happy the way it's
implemented, there should be a better way to just fontify the text after
the current prompt. That should avoid any extreme fontification cases.
>
> If the problem is really in "unneeded comint functionality" (or call it
> "bloat"), that's an option, but of course if we don't know where the
> performance problem comes, we may end up with the same problem anyway.
>
Now about the `comint-postoutput-scroll-to-bottom', this alone can also
make Emacs be extremely irresponsive (pretty much like with the
font-locking enabled). The real culprit of it's slowness is `recenter'
function which seems to get really slow with long lines. Here are the
elp-results with font-lock disabled (with a smaller sample of output):
comint-output-filter 103 29.795948749 0.2892810558
comint-postoutput-scroll-to-bottom 104 28.636891969 0.2753547304
recenter 104 28.635311547 0.2753395341
python-pdbtrack-comint-output-filter-function 104 0.990129131 0.0095204724
comint-watch-for-password-prompt 104 0.0924025480 0.0008884860
> Maybe comint.el could also be changed so that it "wraps" lines if they
> get past some arbitrary maximum length (like 10K chars, for example).
> It wouldn't be a great solution, but if the performance sucks really bad
> past 10K chars, wrapping the line might be a lesser evil.
>
Disabling font-lock and avoiding the `recenter' calls works pretty well,
so I rather focus on improving those than modifying comint to workaround
this.
As a final related note, to avoid unnecessary filters, I think the
`inferior-python-mode' should set the `comint-output-filter-functions'
to a minimum and point users to append custom desired filters using the
`inferior-python-mode-hook'.
Regards,
Fabián
This bug report was last modified 10 years and 304 days ago.
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