[PD] Gem performance tests?

derek holzer derek at x-i.net
Tue Apr 19 22:10:25 CEST 2005

Hi Mike,

Mike Wozniewski wrote:

> - Differences between Linux kernels - particularly compared with the 
> optimized PlanetCCRMA kernel.
> - The benefit of the -rt (realtime performance) option.

I'm afraid that the CCRMA kernel probably doesn't give you much of an 
edge over any other kernel in this case. Neither would -rt AFAIK. All of 
this has to do with audio optimizations, which is pretty moot for GEM 
unless you are doing audio with it. My understanding is that OpenGL is 
working primarily in the hardware, so the dataflow in PD which sends 
instructions to the GEM objects (which then send instructions to the 
video card) probably isn't chewing up so much resources that low-latency 
or preemptive kernel patches will make a noticable difference.

So what will give you an edge would be good video drivers with properly 
configured OpenGL support. For NVidia and Radeon cards, for example, 
often the "best" drivers (in terms of performance) are still the 
closed-source, non-free drivers released by the manufacturers. The X11 
drivers and other free + open source ones seem noticably slower.

I'm not sure what drivers are included in CCRMA, but I'd bet that they 
are not compiled into the kernel, but are rather external modules if you 
have a dedicated graphics card. RedHat/Fedora, SuSE and others most 
often use the non-free binary drivers, while Debian, Gentoo and similar 
users choose at install time the free or non-free options.

My experience is that NVidia hardware with non-free drivers seems to 
work better for OpenGL than Radeon with any drivers on Linux, but for 
some this is the devil's road ;-) If others on the list have had better 
luck with the the free video drivers, please speak up. I'd be curious to 


derek holzer ::: http://www.umatic.nl
---Oblique Strategy # 56:
"Do the washing up"

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