Quad Core + 2 GPUs, but can only run 5 WUs.


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Questions and Answers : GPU applications : Quad Core + 2 GPUs, but can only run 5 WUs.

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Profile woodyrox
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Message 1168465 - Posted: 6 Nov 2011, 1:02:33 UTC

So I installed a second GPU in my quad core system and created the cc_config file with the instructions for boinc to use it. That worked, and now my system is crunching with 2 gpus. Problem is, it only runs 3 of the 4 available CPU cores. If I stop the GPUs, the other core picks up another WU. As soon as the gpus start, I'm back to 3 cores. So a max of 5, not 6, tasks run at a time. Also, this system started pre-empting many tasks. I've got 11 pre-empted right now and don't know if that's related. Seems like boinc isn't figuring out the expected completion time correctly for the slower gpu.

Any ideas what's going on here?
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Message 1168482 - Posted: 6 Nov 2011, 1:56:30 UTC - in response to Message 1168465.

My guess is you are running stock apps and you will see that is is using something like 0.66 CPU's + 1 Nvidia GPU.

With each GPU unit being crunched it uses up more than 1 CPU core.

Only way to combat that would be to use an app_info to specify that it only use something like 0.04 CPU.

There is also the optimized apps that will do the work for you.
http://lunatics.kwsn.net/index.php?module=Downloads;catd=9
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Message 1168494 - Posted: 6 Nov 2011, 2:24:13 UTC

Yes, you're right. 0.60 cpu is what each gpu taks says. When I look at my windows task manager performance monitor, and add up the % usage for my 4 cores I get about 320% out of a maximum 400. So there's some horsepower available which is not being used.

Is it beneficial to reduce the amount of cpu allocated per gpu task? If so, how do I do it?
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Message 1168512 - Posted: 6 Nov 2011, 3:09:20 UTC
Last modified: 6 Nov 2011, 3:10:17 UTC

Easiest way is the optimized apps as it will install the app_info file that will take it down to 0.04 CPU. That works just fine as the CPU is only used to load the GPU and then goes idle.

For that system you would want this installer and then choose the SSE3 AMD version and the x38 cuda option.

The only caveat is if you use an app_info you will have to keep an eye on the forums for when newer versions are released so you can upgrade to the newer versions.
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Message 1168763 - Posted: 6 Nov 2011, 21:46:36 UTC - in response to Message 1168512.

Thanks for your guidance. I did as you said and everything worked as you predicted. All of my cores are now pegged at a 100, and I've got 6 tasks crunching simultaneously. The install was very easy, and I'll be doing this for my other AMD crunchers as well.

Which install settings should I use for my intel crunchers? I've got some core 2 duos and a Pentium D.
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Message 1168777 - Posted: 6 Nov 2011, 22:30:28 UTC

The Pentium D can do SSE3 and the C2D's can do SSSE3.
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Message 1172553 - Posted: 20 Nov 2011, 20:14:46 UTC - in response to Message 1168777.

I installed app_info on all of my intel and amd windows crunchers. It's made a huge difference. I've done some hardware upgrades as well so I can't tell for sure what the performance improvement attributed to app_info was but on the one Core 2 machine I didn't upgrade, it was at least 10%, maybe 15. Overall my RAC went up at least 40% and is still rising.

My quad-core AMD with 2 GPUs subsequently ate a power supply. I replaced it with a heftier unit, but have a feeling it too is under-rated now that all CPUs and GPUs are running 100%.

Thanks for your suggestion. It helped a lot.
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Questions and Answers : GPU applications : Quad Core + 2 GPUs, but can only run 5 WUs.

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