Bug#451511: xserver-xorg-video-ati: The ati driver unexpectedly seems to perform worse than the VESA driver

[Helge Hafting]

Brice Goglin wrote:
> Helge Hafting wrote:
>   
>> Minor severity as the driver works as intended.
>>
>> I find the low performance odd though. If the accelerator hardware
>> is slower than VESA for some operations, then surely the unaccelerated VESA
>> way could be used for those things. So it seems to me it doesn't
>> need to be slower in any cases.
>>
>>
>> My testcase is to play the game cuyo at levels 2 or 9. (package cuyo)
>> This is a tetris-like 2D game. It updated the screen 10 times
>> a second, and has a irritating failure mode: If it can't
>> finish drawing in 1/10s, then it refuse to take input 
>> until the drawing queue clears. So it may break very noticeably
>> when there is too much animation going on.
>>
>> Now, perhaps that isn't the best way to design a game, but
>> it shows a performance problem.
>>
>> The ati driver (and the NV driver) easily falls into this trap when
>> there is lots of animation in the cuyo window. The game
>> becomes quite unplayable.
>>
>> This simply doesn't happen with the VESA driver. CPU load stays
>> below 25% always.
>>
>> The processor in this case is a 2.4GHz pentium-M,
>> lspci shows:
>> 01:00.0 VGA compatible controller: ATI Technologies Inc Radeon RV100 QY
>> [Radeon 7000/VE]
>>
>> Another machine with a pci radeon 9200 SE and a 1.8GHz opteron
>> shows the same problem.
>>
>> A third machine with a 1.8Ghz core duo and a nvidia card has
>> this problem too, but of course that is a different package
>>     
>
> Can you try with
> 	Option "AccelMethod" "EXA"
> in the Device section of your xorg.conf?
>   
Thanks for the tip - this change made tremendous difference.
Using the ATI driver, the game is now as snappy as VESA - and
X probably respond better to bigger drawing jobs.

The EXA option solved my problem completely.  :-)

Helge Hafting