Re: Xfree86.0 high CPU in 1280x768

Mark Vojkovich wrote:
> On Tue, 6 Jun 2006, Barry Scott wrote:
>
>   
>> I'm seeing the X process take a lot more CPU time to run any workload in
>> 1280x768 compared to a standard VGA mode like 1280x1024.
>>
>> For example running a text scrolling app (lots of XCopyArea calls) I see the
>> following CPU usage figures:
>>
>> 1280x1024:  6.75%
>> 1280x768:  10.53%
>>
>> top shows that the X process is the only one to show a change between
>> the two modes.
>>
>> With XVIDEO apps the difference is from 50% to 70% to play a movie.
>>
>> This happens with the  i810 driver and the via driver so  I don't think
>> its a driver
>> specific issue. I think that X is changing its behavior.
>>     
>
>    I seriously doubt that.
>
>   
>> Is it possible that X has turned off it acceleration in 1280x768 mode?
>>     
>
>   "X" doesn't have anything to do with acceleration.  This is entirely
> a driver/HW issue.
>   
I'm surprised that XAA has nothing to do with the X core. I'd have assumed
that if the driver supports a speed up then X uses it otherwise X falls 
back to
none accelerated algorithm. But if you say its all in the driver I guess 
that
means that both the via and the i810 driver have the same bug in them.

>> What can I look at to find out what the problem is?
>>     
>
>     Is your refresh rate the same in both cases?  Integrated
> graphics have peculiar performance characteristics because the
> graphics hardware shares memory bandwidth with the CPU.
>   
Refresh rate is 60Hz in both cases. So I assume that its not a memory
bandwidth change as you suggest.

Where should I look to get some data to work on?

Barry