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  • Latest Post - ‏2013-07-08T12:06:16Z by JLGuyot
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Pinned topic Question about NMON Run Queue Size

‏2013-07-01T12:56:09Z |

I have a P7 795 (SMT-4)  LPAR with 1.5 entitled CPUs and 8 virtual CPUs.  I create daily NMON files with 1 minute snapshots.

During my peak busy period there are at most 3 physical CPU units used.  Generally, during steady state there are 1.8  physical CPU units used on average.

However, I noticed the RunQueue is continually reporting an averaage value of 4.

Why is my RunQueue always occupied when I have 8 virtual CPUs?

 

 

  • JLGuyot
    JLGuyot
    4 Posts

    Re: Question about NMON Run Queue Size

    ‏2013-07-08T12:06:16Z  

    Run queue gives an information on the processes running at the same time, scheduled or waiting for a schedule.

    Since you have 8 VP on a SMT-4, you have 32 Logical CPU, which mean you could have a run queue of 32, without much to worry about.

    In details, it's not always true, because each process doesn't require the same amount of CPU cycles, but that's a general indicator.

    If i'm not mistaken, there's in fact a run queue for each logical CPU and the value given by nmon runqueue is the sum of them all.