[GEM-dev] removing performance killer : was Re: performance question with linux and nvidia

[cyrille henry]

hello,

i've got answer to this questions.

First : The bottleneck of the test patch i send is the fillrate.

from : http://en.wikipedia.org/wiki/Fillrate
"the importance of the fillrate as a measurement of performance has declined as the bottleneck in graphics applications has shifted."
So this 3 card have about the same fillrate, even if they are 5 years difference between them.
(and jack GPU have a higher fillrate).



about the 2nd question , i found the performance killer.
it's the GL_LIGHT_MODEL_TWO_SIDE option.
when disable, performance are as expected.

since it is recommended for performance reason to disable this option, it's probable that nvidia has no plan to fix this.
So, i think we have to do something in Gem. Changing the default setting is probably not recomended for compatibility reason, even if most of the time diference will be small.

But we have to think of an easy way to disable this.

any idea?
a message to gemwin?


Cyrille

Le 24/01/2011 19:27, cyrille henry a écrit :
> hello,
>
> i've got performance question regarding Gem an openGL.
>
> i made a test using an OS on a custom liveUSB, so that i can have the same software environment on 3 different computers:
> ubuntu 10.04, NVIDIA driver v270, pd vanilla 42.5, and Gem svn.
>
> this computer are:
>
> very old laptop:
> intel core 2 / GeforceGo 7700M
>
> old laptop:
> intel core 2 duo / Geforce 9650M gt
>
> new laptop:
> intel core i7 / Geforce GT 425M
>
> i made a test with glsl performance, and everything is normal : a newer computer is many time faster than the older.
>
>
> BUT, using a very simple patch (like attached), drawing only many time the same square, i can't see any really significant performance difference.
>
> how could that be? what can be the botleneck?
> (with "lighting 0", i can draw about 400 square before the fps goes down)
>
>
>
> but i've got a bigger problem :
> with "lighting 1", the 2 old laptop can draw about 10% less square (than with lighting 0). but the new one can draw only 3 times less square.
> So the new laptop is lot's slower than the old one when light is on.
>
> does anyone already experience something like this?
> any idea why, and how to solve this?
>
> thanks
> Cyrille
>
>
>
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