[Interest] Qt 5.0.2 speed and widgets

Frederik Gladhorn frederik.gladhorn at digia.com
Mon Apr 15 13:54:39 CEST 2013


Mandag 15. april 2013 10.34.16 skrev Philippe:
> I think I have found the problem: the qaccessible interface...
> 
> While my program was kind of hanging during those long seconds, I have
> broken several times in the debugger, and saw that some accessibility
> code was being executed. Then I did this quick Qt change:
> in qaccessible.cpp
> QAccessible::queryAccessibleInterface(...)
> I insert "return 0;" at the start...
> et voilà, back to normal speed! (actually, a 20% reduction compared to
> 4.8, but this is the day and night compared to before).
> This code change is a dirty hack of course, but it simply make Qt 5 usable
> again for me...
> 
> There is definitly something wrong on the Windows accessibility code...

I suspect it is mostly debug output which actually slows down things. We have 
cleaned it up for Qt 5.1 which will be the next release.

It would be very interesting if you could run the same with the Qt 5.1.0 
alpha. We fixed several issues there (especially with debug output and 
warnings and also QGraphicsView) and improved performance of accessibility by 
introducing a cache.

There is one more patch pending to make accessibility get even less in the way 
when it's inactive (https://codereview.qt-project.org/#change,52194).
If you still experience a slowdown with 5.1, please let me know. It would be 
good to get that fixed.

If you test again, please let me know if you have the accessibility plugins 
installed in the Qt version you are testing (qtaccessiblewidgets.dll).

Greetings
Frederik


> 
> Philippe
> 
> On Mon, 15 Apr 2013 07:45:55 +0200
> 
> "Michael Klank" <michael.klank at amk-antriebe.de> wrote:
> > We have a similar problem here. I did compare a small (bigxml) program
> > from
> > http://qt-project.org/ which reads an xml file in a QTreeWidget and
> > expands all nodes. The test xml file is 2MB. Qt5.0.2 MSVC2012 64Bit/32Bit
> > is up to 20x slower than Qt4.8.0 MSVC2010 32Bit, in release mode!!!
> > That's strange. And I didn't say anything from debug mode!
> > 
> > 
> > -----Ursprüngliche Nachricht-----
> > Von: interest-bounces+michael.klank=amk-antriebe.de at qt-project.org
> > [mailto:interest-bounces+michael.klank=amk-antriebe.de at qt-project.org] Im
> > Auftrag von ???? ??????????
> > Gesendet: Sonntag, 14. April 2013 20:14
> > An: Philippe
> > Cc: interest at qt-project.org
> > Betreff: Re: [Interest] Qt 5.0.2 speed and widgets
> > 
> > Yes, we are having same problem here. Same setup, AFAIK.
> > 
> > Don't know what's causing problem.
> > 
> > Also, Mac OS has no noticeable speed regressions, it seems
> > Windows-specific
> > issue.
> > 
> > ???? ??????????
> > 
> > 14.04.2013, ? 21:55, Philippe <philwave at gmail.com> ???????(?):
> > > Compared to Qt 4.8.x, I experiment a very sensible reduction of speed
> > > in 5.0.2 when widgets are created or complex windows activated.
> > > In Release mode this is "sort of acceptable",... maybe half speed.
> > > But in debug mode, this is dramatically slower, up to 6x slower than
> > > in 4.8.3.
> > > 
> > > This is not a painting issue as the speed inside a window has been
> > > measured to be sensibly the same to 4.8.x (using ANGLE).
> > > 
> > > Anyone else sees the same? Any known reason for this?
> > > 
> > > Setup: Windows 7, Visual 2010, Qt 32 bit, *very* fast computer.
> > > 
> > > Philippe
> > 
> > _______________________________________________
> > Interest mailing list
> > Interest at qt-project.org
> > http://lists.qt-project.org/mailman/listinfo/interest
> 
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-- 
Best regards,
Frederik Gladhorn
Senior Software Engineer - Digia, Qt
Visit us on: http://qt.digia.com



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