GNU bug report logs -
#8890
23.3; message writing slows emacs
Previous Next
Reported by: Dave Abrahams <dave <at> boostpro.com>
Date: Sat, 18 Jun 2011 16:46:02 UTC
Severity: normal
Found in version 23.3
Fixed in version 29.1
Done: Lars Ingebrigtsen <larsi <at> gnus.org>
Bug is archived. No further changes may be made.
Full log
Message #41 received at 8890 <at> debbugs.gnu.org (full text, mbox):
> From: Dave Abrahams <dave <at> boostpro.com>
> Cc: Lars Magne Ingebrigtsen <larsi <at> gnus.org>, 8890 <at> debbugs.gnu.org
> Date: Sun, 11 Sep 2011 12:39:23 -0400
>
> >> Emacs does clever screen updates, though. So if the only thing that
> >> changes is the number before the percentage, Emacs won't repaint the
> >> entire line, I think?
> >
> > True. Like I said, redisplay of the echo area is very fast.
>
> I don't think it's clever enough. Try this:
>
> --8<---------------cut here---------------start------------->8---
> (let (timings)
> (dolist (reps '(1 10))
> (let ((start-time (current-time)))
> (loop for x to 10000 do
> (loop repeat reps do
> (message "message #%s" x)))
> (push (time-subtract (current-time) start-time) timings)))
> (message "%s" (mapcar 'time-to-seconds timings)))
> --8<---------------cut here---------------end--------------->8---
>
> I get (29.539774 2.514761)
>
> I think this shows that it takes (more than) 10x as long to write out
> the same message 10 times as it does to write it out once.
My results are different:
. in a GUI session: (16.172 2.891)
. in a -nw (TTY) session: (26.125 4.734)
The above is from an unoptimized build. Here are timings from an
optimized build:
. GUI session: (10.875 2.0)
. TTY: (19.313 3.453)
This shows that it takes 45% _less_ time to write the same message 10
times than 10x time to write the message once.
So at best the numbers are inconclusive.
Anyway, I know for a fact that Emacs does optimize screen writes in
this case. Look at the function dispnew.c:update_text_area, around
lines 3784 to 3967. I actually put a breakpoint there and saw that
only the changing number is being redrawn while running your test
code. E.g., on line 3885, I see i = 9 while stop = 11, which means
Emacs will redraw only 2 characters.
This bug report was last modified 3 years and 45 days ago.
Previous Next
GNU bug tracking system
Copyright (C) 1999 Darren O. Benham,
1997,2003 nCipher Corporation Ltd,
1994-97 Ian Jackson.