Is there any performance increase by using the "vcpu" option in BOINC ?


Message boards : Number crunching : Is there any performance increase by using the "vcpu" option in BOINC ?

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Rantanplan

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Message 1595 - Posted: 27 Aug 2013, 17:22:57 UTC

Last modified: 27 Aug 2013, 17:25:43 UTC
Question above !

Any interesting results ?

Greetings *wave*
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Rantanplan

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Message 1596 - Posted: 27 Aug 2013, 18:39:31 UTC - in response to Message 1595.  

Last modified: 27 Aug 2013, 19:17:35 UTC
uuhhwww, i went wrong, is the "ncpu" option in BOINC, sorry...

ok changed ncpu to 8 cores using a i5 Ivy , all different results by running times, but shorter cpu time, courios..
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Rantanplan

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Message 1599 - Posted: 27 Aug 2013, 20:32:25 UTC - in response to Message 1596.  

Last modified: 27 Aug 2013, 20:56:33 UTC
oops, disgusting running times , reduced to 6 cores...

ok, now i got more moderate runtimes between 35 and 41 minutes per wu.

thats 10 to 16 minutes slower than running 4 cores...

Is that an advantage ?
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Message 1603 - Posted: 27 Aug 2013, 21:07:24 UTC - in response to Message 1599.  

Last modified: 27 Aug 2013, 21:10:58 UTC
I think not. Tasks will block each other on FPU/SSE.
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Rantanplan

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Message 1604 - Posted: 27 Aug 2013, 21:14:27 UTC - in response to Message 1603.  

Last modified: 27 Aug 2013, 21:34:35 UTC
ok , thx , i am trying about 5 cores now, must be then like hyperthreading on 25% each core, i will see the results.

No better results so far, i will adjust my bios settings now, what ever it is, perhaps i can fix it !?

It dont happen much, same result, i think it could better run on linux as on w7.

Arent it ? ;)
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Message 1605 - Posted: 27 Aug 2013, 22:18:05 UTC

Last modified: 27 Aug 2013, 22:19:48 UTC
There is no advantage to setting ncpus to a value higher than your physical thread count (as intel now calls it). For an i5 that would be 4 and an i7 with hyper threading enabled to 8 (or 12 depending on model).

If you set it higher BOINC will try and run more tasks than the CPU can so it then has to swap stuff in and out which slows it down. Quite often I leave a thread free when running GPU work to save swapping.
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Message boards : Number crunching : Is there any performance increase by using the "vcpu" option in BOINC ?