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Clue less abt CPU Time variation

 
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sandeep1dimri

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Joined: 30 Oct 2006
Posts: 76

PostPosted: Wed Dec 06, 2006 12:26 pm    Post subject: Clue less abt CPU Time variation
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Hi!!

Why my same job is taking different CPU minutes ? I have not changed anything i just submited my job again. So for every run the CPU time is different .i Can understand that the variation in the elasped time but i m clueless abt the CPU time variation. Please let me have the solution of this variation.



Thanks in advance
Sandeep
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rajandhla

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Joined: 18 Oct 2005
Posts: 182
Location: Luton UK

PostPosted: Wed Dec 06, 2006 2:39 pm    Post subject:
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CPU time is allocated in slots not contigious. For High priority jobs cpu will be allocated first. It is one of the reason for as It varies every time
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sandeep1dimri

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PostPosted: Wed Dec 06, 2006 3:20 pm    Post subject:
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Hi Raj but in that case elaspased time should vary not the CPU time.
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Phrzby Phil

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Joined: 31 Oct 2006
Posts: 962
Location: Richmond, Virginia

PostPosted: Sat Dec 09, 2006 1:46 am    Post subject:
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Let's see your actual numbers.
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dick scherrer

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Joined: 23 Nov 2006
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Location: Inside the Matrix

PostPosted: Sat Dec 09, 2006 3:13 am    Post subject:
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Hello,

Is it possible that the content of the input file(s) have changed between runs?

If the input is on tape, is the same tape drive allocated for the runs that show different cpu times? If there was a lot of retry operations (temporary i/o errors) this may cause more cpu time to be required.

Does the clock time change as well as the cpu time?
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MFRASHEED

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Joined: 14 Jun 2005
Posts: 186
Location: USA

PostPosted: Sat Dec 09, 2006 4:12 am    Post subject: Re: Clue less abt CPU Time variation
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I think there are lots of other factors which contribute to variation of CPU Time. And it not just on mainframes but other systems too, found one article which tries to explain the variation.

http://www.solarisinternals.com/si/reading/CMG98cpu.pdf
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