How many CPUs can BOINC handle?

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Message 10969 - Posted: 9 Jun 2011, 17:50:49 UTC




Sunflower is only using 60 CPUs - where are the other 20?
Is this a BURP limitation? BOINC limitation?

Running W2K8-R2 Datacenter Edition... so I can see all 80, but not use them all?


(I know crazy problem to have eh?)
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Profile Janus
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Message 10970 - Posted: 10 Jun 2011, 5:59:19 UTC - in response to Message 10969.  
Last modified: 10 Jun 2011, 6:01:50 UTC

Hehe, very interesting problem! I think it is actually a combination of the two:

I'm surprised that the BOINC default mt app plan limit isn't 64 CPUs though, since that is what it should be (maybe a bug?):
MT app plan: An application that can use anywhere from 1 to 64 threads, and whose speedup with N CPUs is .95N.

It should leave the remaining CPUs to other projects.

However, the fact that it is running on 60 out of 80 CPUs but "only" using around 50% (like 40 CPUs total) is related to the way that Blender renders stuff, it pauses some of its threads while waiting for others to complete when switching layers.

Still a very impressive piece of machinery you've got there! I assume that's actually 40 cores hyperthreaded?
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Message 10971 - Posted: 10 Jun 2011, 19:45:04 UTC

it is a windows limitation and how windows is grouping your cpus/cores.
each physical cpu is a node. nodes are assigned into groups which can have max. 64 logical processors. because you have more than 64 logical processors, windows creates 2 groups. every group must consist of at least one node.
thats a short explaination for your 60/20 problem.

also see here:
http://msdn.microsoft.com/en-us/library/dd405503%28VS.85%29.aspx

and here:
http://msdn.microsoft.com/en-us/library/aa363804%28v=VS.85%29.aspx
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Message 10972 - Posted: 13 Jun 2011, 15:33:14 UTC - in response to Message 10971.  

it is a windows limitation and how windows is grouping your cpus/cores.
each physical cpu is a node. nodes are assigned into groups which can have max. 64 logical processors. because you have more than 64 logical processors, windows creates 2 groups. every group must consist of at least one node.
thats a short explaination for your 60/20 problem.

also see here:
http://msdn.microsoft.com/en-us/library/dd405503%28VS.85%29.aspx

and here:
http://msdn.microsoft.com/en-us/library/aa363804%28v=VS.85%29.aspx


great info! So would Linux have any similar restrictions? or would that allow more utilization?

oh and @Janus - yes, it's 40 physical cores (4x10) which is hyper-threaded :)
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Message 10973 - Posted: 13 Jun 2011, 22:32:22 UTC - in response to Message 10972.  

linux should use all of your 80 logical processors. just try it ;)
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Message boards : Number crunching : How many CPUs can BOINC handle?