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bug#32729: Xemacs 23 times as fast as GNU Emacs
From: |
Eli Zaretskii |
Subject: |
bug#32729: Xemacs 23 times as fast as GNU Emacs |
Date: |
Mon, 14 Oct 2019 12:15:09 +0300 |
> From: Lars Ingebrigtsen <larsi@gnus.org>
> Cc: benjamin.benninghofen@airbus.com, layer@franz.com,
> 32729@debbugs.gnu.org, 32728@debbugs.gnu.org
> Date: Mon, 14 Oct 2019 10:36:11 +0200
>
> Eli Zaretskii <eliz@gnu.org> writes:
>
> > I don't understand what would trigger these callbacks, and how do you
> > specify the region in advance, without knowing what will be inserted.
>
> accept_process_output inserts the data into the buffer and then calls
> the callback with the region in question. Well,
> read_and_dispose_of_process_output, I guess...
Filter functions are called even if the Lisp program never calls
accept-process-output, so your proposal doesn't seem to be equivalent
to what we have now, right?
OTOH, if one has to call accept-process-output, then why do we need
callbacks? Just extend accept-process-output to call a function with
the received output. No?
> > Without understanding this, I don't think I see the utility, and most
> > important: why this would be faster.
>
> It would avoid creating (and garbaging) the strings.
I'm not sure I see how.
The way it works now is that we get the process output as a C string;
we then decode it and make a Lisp string from the result of decoding;
and then we invoke the filter with that Lisp string. (If the filter
is nil, we invoke internal-default-process-filter instead, but it
still gets the text as a string.)
Which part(s) of this will be avoided under your proposal?
> > Btw, unlike what I originally implied, the default filter also
> > receives a Lisp string, so the question why by default reading dd
> > output is so much faster than when you define a non-default filter
> > function still stands.
>
> Oh! That is curious indeed. Are the Lisp_Object strings somehow
> ... special here when they never leave C land?
No, I don't think so.
> The speed differential is completely repeatable... hm... Is the
> only difference that gc isn't given a chance to run in the
> non-filter case?
You could test that hypothesis by setting gc-cons-threshold to a very
high value.
Bottom line: I think we must understand better what takes the time in
your last test case, before we discuss solutions. I'd start by
profiling that with "M-x profiler-start".
- bug#32728: bug#32729: Xemacs 23 times as fast as GNU Emacs, Lars Ingebrigtsen, 2019/10/11
- bug#32728: bug#32729: Xemacs 23 times as fast as GNU Emacs, Lars Ingebrigtsen, 2019/10/13
- bug#32728: bug#32729: Xemacs 23 times as fast as GNU Emacs, Eli Zaretskii, 2019/10/13
- bug#32728: bug#32729: Xemacs 23 times as fast as GNU Emacs, Lars Ingebrigtsen, 2019/10/14
- bug#32728: bug#32729: Xemacs 23 times as fast as GNU Emacs, Eli Zaretskii, 2019/10/14
- bug#32728: bug#32729: Xemacs 23 times as fast as GNU Emacs, Benninghofen, Benjamin Dr., 2019/10/25
- bug#32729: Xemacs 23 times as fast as GNU Emacs, Eli Zaretskii, 2019/10/25
bug#32728: bug#32729: Xemacs 23 times as fast as GNU Emacs, Phil Sainty, 2019/10/13