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  • Latest Post - ‏2011-05-10T20:41:10Z by SystemAdmin
SystemAdmin
SystemAdmin
706 Posts

Pinned topic POWER7 PMCs: Is there a way to estimate memory bandwidth using PMU events?

‏2011-05-04T18:54:26Z |
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We are looking for a way to estimate the actual memory bandwidth on a POWER7 system using the hardware counters.
Updated on 2011-05-10T20:41:10Z at 2011-05-10T20:41:10Z by SystemAdmin
  • SystemAdmin
    SystemAdmin
    706 Posts

    Re: POWER7 PMCs: Is there a way to estimate memory bandwidth using PMU events?

    ‏2011-05-04T19:01:32Z  
    And as always with hardware counters, there's a "it depends" answer emerging.

    Code examples are being built with two counters. The actual derived (estimated) bandwidth would be a formula which is being validated.

    
    PM_MEM0_RQ_DISP - Event counted at memory controller to count memory read dispatches PM_MEM0_WQ_DISP - Event counted at memory controller to count memory write dispatches
    
  • SystemAdmin
    SystemAdmin
    706 Posts

    Re: POWER7 PMCs: Is there a way to estimate memory bandwidth using PMU events?

    ‏2011-05-10T20:41:10Z  
    And as always with hardware counters, there's a "it depends" answer emerging.

    Code examples are being built with two counters. The actual derived (estimated) bandwidth would be a formula which is being validated.

    <pre class="jive-pre"> PM_MEM0_RQ_DISP - Event counted at memory controller to count memory read dispatches PM_MEM0_WQ_DISP - Event counted at memory controller to count memory write dispatches </pre>
    As an update.. there is some peculiar initial behavior with these counters when measuring fairly simple applications. In other words, the pieces are not yet adding up when using "perf". Investigations continue. If you happen to be working in this area and have your own observations, we would like to hear from you.