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Message boards : Number crunching : Work Unit Stated CPU usage 0.981C + 1NV

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archeye
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Message 53410 - Posted: 31 Dec 2019 | 12:28:41 UTC
Last modified: 31 Dec 2019 | 12:30:54 UTC

Now I am happy with the 1NV = 1 x Nvidia GPU

The 0.981C however is something I am less sure of the meaning.

For example when I already have 8 CPU tasks running and using 80 to 90% of a CPU thread then I sort of expected one of these tasks to be bumped but it does not happen.

Can someone explain what 0.981C means when processing alongside a max number of other CPU tasks.

CPU is i7-4790K 4 core and 8 threads, RAM = 32Gb

Thanks
(I could not get the image to display so sry for the link)

[img]https://i.postimg.cc/prN3w8zL/GPU-grid-qu.jpg[/img]

Erich56
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Message 53411 - Posted: 31 Dec 2019 | 12:44:16 UTC

don't worry, this is normal for GPUGRID tasks, regardless which CPU you have.

Zalster
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Message 53413 - Posted: 31 Dec 2019 | 16:38:00 UTC - in response to Message 53410.

Now I am happy with the 1NV = 1 x Nvidia GPU

The 0.981C however is something I am less sure of the meaning.

For example when I already have 8 CPU tasks running and using 80 to 90% of a CPU thread then I sort of expected one of these tasks to be bumped but it does not happen.

Can someone explain what 0.981C means when processing alongside a max number of other CPU tasks.

CPU is i7-4790K 4 core and 8 threads, RAM = 32Gb

Thanks
(I could not get the image to display so sry for the link)

[img]https://i.postimg.cc/prN3w8zL/GPU-grid-qu.jpg[/img]



The 0.981 C is what default amount of CPU thread a work unit should use. It doesn't always use that much or that little. It's more of a guideline. It will use as much CPU resource as it needs to process the work unit. The rest of your question gets into a sticky debate.

If you are running 8 CPU task on a 8 thread CPU and running a single GPU task with a 0.981 C requirement, then you are running 9 tasks! How can that be??? Because, are are not running all 9 task simultaneously. You may think you are but there are momentary brief pauses where there is a shifting of work units across those 8 threads. They only way to prevent that is to set up an affinity lock for each work unit to each thread (something we don't do here) that way a single thread is dedicated specific work unit. In this case, the GPU work unit is going to be stealing processing time on a thread from other work units as it has a higher priority than the CPU work units. You just can't see this infinitesimal pauses as it shifts between tasks. Essentially you are starving the GPU of a thread it needs to process the work unit so it steals it where it can.

Which brings up another question. There aren't any CPU task currently at GPUGrid so I'm guessing you are processing data from another project? Some of us restrict the number of work units from a project on a machine to make sure there is a 1-2 free cores to support the GPU and the OS. How we do this is another debate

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archeye
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Message 53417 - Posted: 31 Dec 2019 | 23:35:28 UTC - in response to Message 53413.

This is far more technical than I was looking for but thanks for the details, it shows me how much I still need to learn :)

On another point, ha, I cant count, when I have 2 GPUGRID GPU tasks running on both my 2 Nvidia cards it does bump one of the already running CPU tasks so then there is x 7 CPU tasks and x 2 GPU Tasks running.

You can see that in the image i have linked in the original post for this thread.

I should pay closer attention to details i guess ;)

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Message boards : Number crunching : Work Unit Stated CPU usage 0.981C + 1NV