Short answer is no. You can't run two CUDA process unless the developer put some contention method to avoid such collisions

Long answer in the CUDA handbook:

Some devices of compute capability 2.0 can execute multiple kernels concurrently. Applications may query this capability by calling cudaGetDeviceProperties() and checking theconcurrentKernels property. The maximum number of kernel launches that a device can execute concurrently is four. A kernel from one CUDA context cannot execute concurrently with a kernel from another CUDA context. Kernels that use many textures or a large amount of local memory are less likely to execute concurrently with other kernels.

--------------------------------------------------------------------- Pedro Paulo de Magalhães Oliveira Junior Diretor de Operações Netfilter & SpeedComm Telecom -- www.netfilter.com.br -- For mobile: http://www.netfilter.com.br/mobile

On Tue, Nov 23, 2010 at 12:03, Marcus N Schmidt m.schmidt@erasmusmc.nlwrote:

I should note that we have a single GeForce GTX 470 card on the workstation and have installed the latest CUDA drivers and toolkit (3.2).

Marcus N Schmidt* Department of Child & Adolescent Psychiatry Erasmus MC Rotterdam, The Netherlands

On Nov 23, 2010, at 2:51 PM, Marcus N Schmidt wrote:

Hello,

Is there a limit to how many processes can use CUDA at the same time? I just setup a new Linux workstation and am delving into FreeSurfer w/ CUDA. I'm getting the following error:

Acquiring CUDA device Using default device CUDA Error in file 'devicemanagement.cu' on line 46 : all CUDA-capable devices are busy or unavailable. Linux rietveld 2.6.18-194.26.1.el5 #1 SMP Tue Nov 9 12:54:20 EST 2010 x86_64 x86_64 x86_64 GNU/Linux

Thanks, Marcus

Marcus N Schmidt* Erasmus MC Rotterdam, The Netherlands

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It depends on the Stream Multiprocessor (SM) constrains --------------------------------------------------------------------- Pedro Paulo de Magalhães Oliveira Junior Diretor de Operações Netfilter & SpeedComm Telecom -- www.netfilter.com.br -- For mobile: http://www.netfilter.com.br/mobile

On Tue, Nov 23, 2010 at 12:25, Richard G. Edgar rge21@nmr.mgh.harvard.eduwrote:

On Tue, 2010-11-23 at 15:03 +0100, Marcus N Schmidt wrote:

...

I should note that we have a single GeForce GTX 470 card on the workstation and have installed the latest CUDA drivers and toolkit (3.2).

...

Is there a limit to how many processes can use CUDA at the same time? I just setup a new Linux workstation and am delving into FreeSurfer w/ CUDA. I'm getting the following error:

Acquiring CUDA device Using default device CUDA Error in file 'devicemanagement.cu' on line 46 : all CUDA-capable devices are busy or unavailable. Linux rietveld 2.6.18-194.26.1.el5 #1 SMP Tue Nov 9 12:54:20 EST 2010 x86_64 x86_64 x86_64 GNU/Linux

None of the code I've written (which includes devicemanagement.cu) imposes limitations - I actually often run more than one GPU job at once on the card. The driver software timeslices the entire card between processes. However, the cards themselves might be set so that only one process can use them at a time (using the nvidia-smi tool) - that's entirely up to the system administrator.

I would not recommend running more than one CUDA process per card routinely - especially not on a low end card like that - since the memory allocations might end up failing, killing the job.

Regards,

Richard

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