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List:       kwin
Subject:    Re: Re: Task switcher extremely slow after upgrading to mesa 9.1
From:       Martin =?ISO-8859-1?Q?Gr=E4=DFlin?= <mgraesslin () kde ! org>
Date:       2013-02-27 10:16:11
Message-ID: 6814516.PSqvvOnpxC () martin-desktop
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On Wednesday 27 February 2013 10:33:49 Stefano Avallone wrote:
> On Wednesday 27 February 2013 10:17:55 Martin Gräßlin wrote:
> > On Wednesday 27 February 2013 09:34:05 Stefano Avallone wrote:
> > > I wanted to open a bug against mesa/intel, but I thought it was better
> > > to
> > > ask an opinion to kwin devs first. Maybe you can provide me with useful
> > > information to pass along to Intel devs.
> > 
> > Thanks for letting us know. Sounds like a problem in the lanczos filter.
> > There are two possibilities:
> > 1. It did not get activated on your system before and now it gets. In that
> > case we should adjust the lanczos filter to ensure that it doesn't get
> > activated
> > 2. There is a change in mesa which causes the regression. That might be a
> > bug on our side or on Mesa's side. Last time we had such an issue the bug
> > was on our side.
> > 
> > So the most important info at this moment is to know whether the Lanczos
> > filter had been working for you before.
> 
> Thanks for your immediate reply.
> 
> How can I know whether the Lanczos filter gets activacted and works?
that's a good question. I just realized that it's not included in any of our 
debug infos and one can only figure out by interpreting some debug messages.

Best way is to enable debug messages for kwin (kdebugdialog section 1212) and 
start kwin from a console. Lanczos is enabled if there is:
KWin::SceneOpenGL2::SceneOpenGL2: OpenGL 2 compositing successfully 
initialized

(important part: it's SceneOpenGL2 and not SceneOpenGL1)

Then trigger the Lanczos filter by using one of the things you observed as 
slow and watch whether there is a message:
"Shader is not valid"

If that message is shown lanczos is not used, if it is not shown it might be 
used. There's no message on success. You can try to make sure it's used by 
using environment variable KWIN_FORCE_LANCZOS=1

If you are able to recompile KWin, just add a debug message in 
lanczosfilter.cpp in line 168

--
Martin Gräßlin
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