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  • 1.  Difference between processing units and virtual processors.

    Posted Sun August 30, 2009 02:45 PM

    Originally posted by: ejk67


    I have one 55A with 2-LPARS the resources equally distributed between both. I have the following listed for "Processing Units" and "Virtual processors" but don't understand the difference between "units" and "virtual". Would some explain?

    Processing units
    Minimum processing units: 2
    Desired processing units: 4
    Maximum processing units: 8

    Virtual processors
    Minimum processing units required for each virtual processor: 0.10
    Minimum virtual processors: 4
    Desired virtual processors: 8
    Maximum virtual processors: 16
    #AIX-Forum


  • 2.  Re: Difference between processing units and virtual processors.

    Posted Tue September 01, 2009 02:54 AM

    Originally posted by: ostost


    Processing units is the amount of physical processor capacity an LPAR will get. Having desired processing units set to 4 means the LPAR can consume the capacity of 4 physical processors (provided that 4 physical processors are available when the LPAR is activated).

    The number of virtual processors decides how many processors the OS running in the LPAR will see. In this case the capacity of the 4 physical processors would be delivered to LPAR through 8 virtual processors. The number of virtual processors also limits the amount of physical CPU an LPAR can consume when running in uncapped mode. In this case in uncapped mode the LPAR cannot get more than 8 physical processors in uncapped mode.
    #AIX-Forum


  • 3.  Re: Difference between processing units and virtual processors.

    Posted Wed September 02, 2009 08:47 AM

    Originally posted by: SystemAdmin


    To add to ostost's reply, processing units also describe the amount of CPU time available for the LPAR in a timeslice. So if the duration of one timeslice is 10ms, the LPAR would get "upto" 40ms from the shared processor pool. Any unused CPU cycles would remain in the shared pool which can be further used by uncapped LPARS.

    Virtual processors is ofcourse the number which the OS sees. But it also means how many threads would be dispatched by the OS at a time. So this number could be increased to get better performance (provided sufficient physical processors exist in the shared pool and the LPAR is uncapped) upto a certain limit after which performance degrades.

    Number of Virtual processors are generally the higher rounded off value of processing units (2.4=3), and increased as required.

    r/
    R
    #AIX-Forum


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