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Re: 78% speed up in CC Mode scrolling.
From: |
Alan Mackenzie |
Subject: |
Re: 78% speed up in CC Mode scrolling. |
Date: |
Sun, 3 Jul 2016 19:39:48 +0000 |
User-agent: |
Mutt/1.5.24 (2015-08-30) |
Hello, Eli.
On Sun, Jul 03, 2016 at 10:27:54PM +0300, Eli Zaretskii wrote:
> > Date: Sun, 3 Jul 2016 18:29:57 +0000
> > From: Alan Mackenzie <address@hidden>
> > Scrolling through emacs-25's xdisp.c, I get the following timings:
> > emacs-25 branch: 45.529s
> > master branch: 25.529s
> > This is a speedup of around 78%.
> Please show your benchmark code, and please tell which compiler
> options were used to build Emacs. Otherwise, I don't know how to
> reproduce this.
(defmacro time-it (&rest forms)
"Time the running of a sequence of forms using `float-time'.
Call like this: \"M-: (time-it (foo ...) (bar ...) ...)\"."
`(let ((start (float-time)))
,@forms
(- (float-time) start)))
(defun time-scroll (&optional arg)
(interactive "P")
(message "%s"
(time-it
(condition-case nil
(while t
(if arg (scroll-down) (scroll-up))
(sit-for 0))
(error nil)))))
Do C-x C-f ..../src/xdisp.c, then without scrolling it otherwise, M-:
(time-scroll). My measurements were done on a Linux virtual tty.
My .configure options were:
./configure --with-tiff=no --with-gif=no --with-gpm
. The default values of CFLAGS, etc., were used.
> > If you frequently hold down C-v or M-v, you are recommended to set
> > `fast-but-imprecise-scrolling' to non-nil.
> What does this recommendation have to do with the speedup?
Nothing, really. But it seemed relevant, perhaps for people running at
low levels of compiler optimisation.
> Thanks.
--
Alan Mackenzie (Nuremberg, Germany).