GNU bug report logs - #32728
Emacs slow when reading process output

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Message #39 received at 32728 <at> debbugs.gnu.org (full text, mbox):

From: Eli Zaretskii <eliz <at> gnu.org>
To: Lars Ingebrigtsen <larsi <at> gnus.org>
Cc: layer <at> franz.com, 32729 <at> debbugs.gnu.org, benjamin.benninghofen <at> airbus.com,
 32728 <at> debbugs.gnu.org
Subject: Re: bug#32729: Xemacs 23 times as fast as GNU Emacs
Date: Sun, 13 Oct 2019 21:46:30 +0300

> From: Lars Ingebrigtsen <larsi <at> gnus.org>
> Cc: benjamin.benninghofen <at> airbus.com,  layer <at> franz.com,
>   32729 <at> debbugs.gnu.org,  32728 <at> debbugs.gnu.org
> Date: Sun, 13 Oct 2019 19:47:16 +0200
> 
> >> Nope.  Does Emacs need to do a lot of recomputing when going to
> >> multibyte buffers?
> >
> > Of course: we try to display the multibyte text as characters, search
> > for fonts, invoke bidi reordering, etc.
> 
> I tried:
> 
> (benchmark-run
>     1
>   (call-process "dd" nil (with-current-buffer
> 			     (get-buffer-create " *zeroes*")
> 			   (set-buffer-multibyte nil)
> 			   (current-buffer))
> 		nil "if=/dev/zero" "bs=4096" "count=250000"))
> 
> and then jumped to the buffer, and Emacs hung anyway.  (That is, I
> killed Emacs after a minute, so I don't know whether it would have
> recovered after a while...)

Do that, _and_ move point to the beginning of the buffer.

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