Xorg/KDE4 slow on ATI

DJ Lucas dj at linuxfromscratch.org
Thu Aug 19 01:48:45 PDT 2010

On 08/19/2010 12:34 AM, Thomas Trepl wrote:
> Hi all,
> long time i was disappointed by the speed of KDE4. Moving, but especially 
> resizing windows was terrible slow, the mouse pointer was always far ahead of 
> the window frame.
> Yesterday I throw "KDE4 slow resize" to google and found a solution in the 
> very first link: http://blog.jasondonenfeld.com/169  There is a link to the 
> solution to the problem i described above. It is a patch to xorg-server. I 
> just recompiled xorg-server-1.7.5 and it works.
> Wau, really cool!!  I think its a must for ATI users!  Maybe someone could 
> make a note in the xorg-server page.

I don't use the ATI proprietary drivers or KDE, but general consensus
suggests that the patch does "the right thing," it just happens not to
work with ATI drivers, or rather the removal of the patch makes ATI
devices behave with some garbage on screen in certain instances, which
is what the original patch was intended to fix.  If I further understand
the conversation, it also introduces a 300ms delay on all other devices
(time for read back).  Taking that into account, the removal of an
upstream addition that actually fixes a problem with most drivers, is
not a good path for BLFS.

The link to the patch can be placed into the wiki, however, I'd much
rather see the conditional enhanced with '&& PIXMAP_PTR_NO_READ ==
"false"' or similar (better name and conditional to be supplied by
somebody who actually understands the code).  Anybody want to do the leg
work?  Assuming that it is even possible, if that were done, and the
default value set to false, it could go into BLFS without question.
Additionally, something like this could be pushed upstream to buy some
time for ATI to provide a workaround or rewrite.

-- DJ Lucas

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