Re: Slow GTK3 redisplay

[Eli Zaretskii <eliz@gnu.org>]

> Date: Mon, 13 Aug 2012 16:41:14 +0400
> From: Dmitry Antipov <dmantipov@yandex.ru>
> 
> Some time ago I did the following simple redisplay benchmark:
> 
> (defun scroll-benchmark ()
>    (interactive)
>    (let ((oldgc gcs-done)
>          (oldtime (float-time)))
>      (condition-case nil (while t (scroll-up) (redisplay))
>        (error (message "GCs: %d Elapsed time: %f seconds"
>                        (- gcs-done oldgc) (- (float-time) oldtime))))))
> 
> And here are some results of running the code above over xdisp.c,
> with different X toolkits and without it. Of course, emacs -Q was used.
> GTK3 is 3.2.4, GTK2 is 2.24.8, OpenMotif is 2.3.3, Xaw3d 1.5E, Xaw 1.0.8.
> 
> Default GUI means menu bar, tool bar and scroll bar enabled. Minimal GUI
> means all of the above is disabled, i.e. the frame state after
> 
> (progn (menu-bar-mode 0) (tool-bar-mode 0) (scroll-bar-mode -1)).
> 
> Numbers are in seconds.
> 
>            Default GUI Minimal GUI
> GTK3:        108          34
> GTK2:         41          34
> OpenMotif:    36          34
> Lucid:        38          34
> None:         36          33
> 
> Here GTK3 GUI is _painfully_ slow. Can someone explain this? Is something
> wrong with my GTK3 setup? Am I running heavyweight theme, or what?

FWIW, there's almost no difference on MS-Windows: 54.8 sec vs 54.05,
so it's similar to other toolkits except GTK3.

Sounds like purely a GTK3 problem (IOW, not interesting as far as
Emacs internals go).

Btw, I hope you know that your benchmark is exceedingly unrealistic,
compared with 90% of redisplay operations in real life.  It can be
used for comparison with itself, but it is not indicative of the
display speed in any way, AFAIU.