Reconciling Load Average and Percentage Idle - Aix

This is a discussion on Reconciling Load Average and Percentage Idle - Aix ; I have a 16-core p570 running an IBM Informix database, and very little else. I sense it's currently substantially over-specd, even at the buiest times. During these busy times the Load Average (as measured by uptime say) rises to as ...

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Thread: Reconciling Load Average and Percentage Idle

  1. Reconciling Load Average and Percentage Idle

    I have a 16-core p570 running an IBM Informix database, and very little
    else. I sense it's currently substantially over-specd, even at the buiest
    times.

    During these busy times the Load Average (as measured by uptime say) rises
    to as high as 3.50. yet the "Percentage Idle" as monitored via topas never
    dips below 85%. How can this be? If the processors are that idle how can I
    be building up a queue on them?

    thx
    Neil



  2. Re: Reconciling Load Average and Percentage Idle

    On Mon, 25 Dec 2006, Neil Truby wrote:

    > I have a 16-core p570 running an IBM Informix database, and very little
    > else. I sense it's currently substantially over-specd, even at the buiest
    > times.
    >
    > During these busy times the Load Average (as measured by uptime say) rises
    > to as high as 3.50. yet the "Percentage Idle" as monitored via topas never
    > dips below 85%. How can this be? If the processors are that idle how can I
    > be building up a queue on them?


    3.5/16 = 0.21

    -s

  3. Re: Reconciling Load Average and Percentage Idle

    >
    > 3.5/16 = 0.21
    >


    Exactly.
    A more verbose comment would have been more helpful for Neil though.

    "The load average is the number of runnable processes over the
    preceding 1-, 5-, 15-minute intervals."
    What this means loosely is that the system would be 100% busy when load
    average equals the number of runqueues (i.e., #cpus, which is 16 in
    your case).

    A load avg of 3.5 means only 21% busy system...so topas correctly
    reported system idle-ness.


  4. Re: Reconciling Load Average and Percentage Idle

    wrote in message
    news:1167125377.508644.44530@h40g2000cwb.googlegro ups.com...
    > >
    >> 3.5/16 = 0.21
    >>

    >
    > Exactly.
    > A more verbose comment would have been more helpful for Neil though.
    >
    > "The load average is the number of runnable processes over the
    > preceding 1-, 5-, 15-minute intervals."
    > What this means loosely is that the system would be 100% busy when load
    > average equals the number of runqueues (i.e., #cpus, which is 16 in
    > your case).
    >
    > A load avg of 3.5 means only 21% busy system...so topas correctly
    > reported system idle-ness.


    Cheers, that's very helpful.



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