Question about CPU use on GPU tasks

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Jacob Johnson Project Donor

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Message 1976427 - Posted: 22 Jan 2019, 12:18:41 UTC

Hello, perhaps this has been answered already but after a bit of searching I could find nothing, perhaps that is because it is a stupid question which has not been asked before. But given my unyielding desire to constantly increase my performance I was wondering what the effect would be if I increased the CPU use on GPU tasks by performing the following changes to the config file.

Current default:
<avg_ncpus>0.04</avg_ncpus>

<max_ncpus>0.2</max_ncpus>

Suggested change:
<avg_ncpus>0.1</avg_ncpus>

<max_ncpus>0.5</max_ncpus>

Would this have a chance of increasing my performance or would it increase the likelihood of error results? I just upgraded from a GTX 1050 Ti to an RTX 2060 so my performance has already received quite the boost this week but as always my thirst for more results has not been quenched, Thanks in advance to anyone who can help, and I apologize for my ignorance if this is either a stupid question or has been answered before.

-Jake
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Message 1976428 - Posted: 22 Jan 2019, 12:27:38 UTC

The "suggested" figures have very little impact on the GPU's performance as the GPU will grab as much CPU as it requires.
What makes a bigger impact is actually having enough CPU cores available for the GPU to grab when needed. There are a number of ways of achieving this, perhaps the simplest is to set the "use % CPU" value in BOINC manager (from the advanced view select "options") and allow one core for each GPU task being run.
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Message 1976431 - Posted: 22 Jan 2019, 12:35:03 UTC - in response to Message 1976428.  

The "suggested" figures have very little impact on the GPU's performance as the GPU will grab as much CPU as it requires.
What makes a bigger impact is actually having enough CPU cores available for the GPU to grab when needed. There are a number of ways of achieving this, perhaps the simplest is to set the "use % CPU" value in BOINC manager (from the advanced view select "options") and allow one core for each GPU task being run.

If you're referring to the Computing Preferences window the only GPU related option I have in there is to "Suspend GPU computing when computer is in use" hence why I have to edit the config files to get anything done. I only leave 1 core unused percentage wise while computing to avoid my computer slowing down or lagging when I'm trying to do something.
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Message 1976437 - Posted: 22 Jan 2019, 13:07:45 UTC

No - I'm referring to the "computing options" within the BOINC manager - "Use % CPU".
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Message 1976444 - Posted: 22 Jan 2019, 13:47:58 UTC - in response to Message 1976437.  

I can't seem to find that area.
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Message 1976447 - Posted: 22 Jan 2019, 14:01:38 UTC

BOINC manager (on your computer, not the website)
"Advanced view"
"options" tab
"computing options"
There are then four or five tabs, on one of them is a line "Use x% of CPU". By default this is set to 100%, but you can set it to anything you like, but it is best to work out how many cores you want to reserve, and then work out what % you are going to use from that.
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Message 1976449 - Posted: 22 Jan 2019, 14:03:20 UTC - in response to Message 1976444.  
Last modified: 22 Jan 2019, 14:04:10 UTC

Go to your boinc manager and click on options from the pull down menus. Select computing preferences. This is on your computer not the seti@home website.

As stated before, to get the best use out of your computer you should have a free thread for each work unit run on GPU in your system. The 0.04 is more of a "guideline" than a hard rule for how much cpu is used. The GPU will use as much as it needs to complete the task, sometime all the way up to 1 full thread. Thus, the recommendation just to set it at 1.
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Message 1976454 - Posted: 22 Jan 2019, 14:10:18 UTC

What I learned hard way CPU power is needed only when GPU task (SoG) "starts". After GPU kicks in CPU wont do any "real job", just polls GPU like crazy wasting 1 CPU core per GPU task.
There are some cmdline options, that reduces CPU usage like -use_sleep and -sbs (buffer size in megabytes, like -sbs 512).
It is still recommended to leave 1 CPU core to feed GPU task so you can get maximum performance out of GPU, especially to start and end the task as fast as possible.
So answer to original question: That setting does not do anything. Leave 1 CPU thread / GPU task free and do other optimizations, like i mentioned before. Try to calculate 2 tasks at once on GPU.
RTX2060 is pretty new and I don't have any experience optimizing RTX architecture cards anyway.
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Message boards : Number crunching : Question about CPU use on GPU tasks


 
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