Bug#790663: Extremely slow window dragging and very poor performance with KMS activated on RV100/M6 [Rage/Radeon Mobility Series]

Michel Dänzer michel at daenzer.net
Wed Jul 1 20:39:18 PDT 2015

On 02.07.2015 01:39, Alfonso García wrote:
> NOTE: I insists that with the previous version of driver (Debian 7) I didn't
> have any problem, all works fine. All stop working with the upgrade.

There's no going back to UMS, you have to find some kind of solution
with KMS.

> On 01/07/15, Michel Dänzer wrote:
>> On 01.07.2015 01:44, alfon wrote:
>>> Section "Extensions"
>>> 	Option		"Composite"		"Disable"
>>> EndSection
>> Why are you disabling this? If the desktop environment (DE) you're using
>> (which is it?) supports compositing, that might alleviate the problem.
> I really don't know why I disabled this, I just was proving different
> options.
> I'm working with the OpenBox window manager.

Can you try if a simple compositing manager (e.g. xcompmgr -a) helps
with the problem (with the options below commented out)?

>>> 	Option          "EXAVSync"              "on"
>> [...]
>>> 	Option 		"ColorTiling"		"off"
>>> 	Option 		"ColorTiling2D" 	"off"
>>> 	Option          "EXAPixmaps"            "on"
>> Does commenting out these options help?
> No,

Please provide /var/log/Xorg.0.log corresponding to commenting out
everything I recommended in xorg.conf.

> the only thing that help something is turned off accel:
> Option "Accel" "off"
> If I do that, I can get an usable X environment. Which it is paradoxical,
> because I'm working without graphic acceleration

Your GPU has a very limited amount of VRAM, so the kernel radeon driver
probably has to migrate buffers between VRAM and GTT a lot, which slows
things down. Disabling Option "EXAPixmaps" (which is the default for
that small amount of VRAM) should avoid that.

Earthling Michel Dänzer               |               http://www.amd.com
Libre software enthusiast             |             Mesa and X developer

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