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Old 08-17-06, 09:40 PM   #15
quokka1
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Join Date: Dec 2005
Posts: 14
Default Re: Poor Xinerama Performance

Quote:
Originally Posted by netllama
The attached bug report indicates that you're using 1.0-8178, not 1.0-8762 (which doesn't require any patches). I'd like to see a bug report against 1.0-8762.

Also, note the following warnings in your X log, which would certainly explain high CPU usage:
(WW) NVIDIA(2): The GPU driving screen 2 is incompatible with the rest of the
(WW) NVIDIA(2): GPUs composing the desktop. OpenGL rendering will be
(WW) NVIDIA(2): disabled on screen 2.
(WW) NVIDIA(3): The GPU driving screen 3 is incompatible with the rest of the
(WW) NVIDIA(3): GPUs composing the desktop. OpenGL rendering will be
(WW) NVIDIA(3): disabled on screen 3.
(WW) NVIDIA(4): The GPU driving screen 4 is incompatible with the rest of the
(WW) NVIDIA(4): GPUs composing the desktop. OpenGL rendering will be
(WW) NVIDIA(4): disabled on screen 4.
(WW) NVIDIA(5): The GPU driving screen 5 is incompatible with the rest of the
(WW) NVIDIA(5): GPUs composing the desktop. OpenGL rendering will be
(WW) NVIDIA(5): disabled on screen 5.

I was under the impression that the test app that you were providing was going to provide a quantifiable measurement of performance, and it seems that your determination is based on comparing CPU usage, which will likely be specific to your hardware setup. Do you have a measurable way of benchmarking this performance?

Also, is the performance problem evident if you're using just two displays with Xinerama?

Thanks,
Lonni
I will try just two screens with Xinerama. I did try 1.0-8762 with a 2.6.17 kernel and it was no better, but I will try again and post a bug report.

As for the OpenGL warnings, are these really relevent ? I'm not an expert here, but Java/Swing doen't use OpenGL unless you tell it to on the command line. I think it is experimental in JDK 1.5 and will become supported in Mustang (1.6).

I'm not 100% convinced that the AGP card is an NVS 280 (maybe 200 ?). Is there an easy way to identify it ? If it was a 200 would this cause the OpenGL warnings ?

Here is the lspci output for the AGP card:

0000:01:00.0 VGA compatible controller: nVidia Corporation NV17GL [Quadro4 200/400 NVS] (rev a3)


The performance is so poor that you don't need to measure it - you can see it. The case where CPU utilization goes to 100% and the Java app cannot manage to update a JTextField 100 times a second is just plain wrong (by a couple of orders of magnitude) - on any modern processor. Whether this is a problem with the Nvidia driver, Xinerama, or some local config or hardware issue I can't say.

A final question. Could this be related to agpgart ? Is it worth giving the Nvidia version a try ?

Last edited by quokka1; 08-17-06 at 09:58 PM.
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