2 replies Latest Post - ‏2013-07-15T08:44:41Z by R2R4_Ivan_NG
2 Posts

Pinned topic How to interpert and link the CPU_ALL, CPU_SUMM and PCPU_ALL tags?

‏2013-07-11T09:53:35Z |

Hi all. I am analyzing one of the clients' AIX. I found in some interpertion between the CPU_ALL, CPU_SUMM and PCPU_ALL tags.So could you pls tell me how to interpert and link up these CPU usage tags? Thank you.

P740 LPAR info
Number Of Processors: 4 ( enable SMT-4)
Total number of thread is 16

May I know how to link up the CPU_ALL, CPU_SUMM and PCPU_ALL usage?
Focus on the Peak CPU usage period from 09:00 to 10:00
CPU_ALL chart shows the usage is 84%
CPU_SUMM chart shows the core and thread usage are 45% and 32% respectively
PCPU_ALL chart shows the usage is 3.4 at most


  • MrBhatt
    11 Posts

    Re: How to interpert and link the CPU_ALL, CPU_SUMM and PCPU_ALL tags?

    ‏2013-07-14T18:56:40Z  in response to R2R4_Ivan_NG

        -Since from the PCPU chart i see Entitled capacity average as 4, i would assume this partition is not participating in playing with shared CPU cycles and would have been a 4 CPU dedicated / capped partition
        -To figure out the max CPU consumed from PCPU_ALL charts, you have taken into account only the user part. Which is not correct, since there is system PCPU component also to be factored for this.
            I would say to derive the number of PCPU your system is consuming at some point o
        time, probably a line chart over the period of time must have made better sense.what is given in this chart is only full day avg. wavg & max. and tough to make point-in-time usage observation from it...
        -This would be the best candidate to figure out point-in time CPU usage by the currently configured type of partition.
        -For the duration you are referring it shows b/w 80-90% of CPU capacity (4 cores) in use
        -This would come out to b/w 3.2-3.6 cores

        -I understand the continuous red line at 90 is not a part of standard chart and have been drawn by you for your own analysis
        -Since this is a SMT enabled partition, you can observe 4 LCPUs against each of the assigned processor (core in your case)
        -And since we know that AIX in the default behavior (recent changed with 6.1TL08) would favor primary threads for running workload before making secondary and tertiary a candidate, this is what you see here. Primary and secondary thread of each of the processor is loaded more as compared to tertiary thread.
        -Good, I can say you can put more workload and can see tertiary threads start working for you.

        -I have not never came across this chart personally, but can make some guess in the current situation
        -Since we know in SMT mode , a single SMT thread would never consume the whole amount of physical resources on the physical processor and AIX reporting mechanism has also been enhanced to report the same for Power6/Power7. Hence what you see in chart-4 against each of the core is the % of resources consumed by all the LCPUs (4 on each core) on that specific core.
        -Looking at this you can make some guess on what % of your physical core resources have been made busy by all the SMT threads (hardware thread context) out of it

    You can still load you system further and pump up more work, provided your reporting tool wont spam you inbox with CPU usage going very high (above 90%) mails ;-)

    You might be interested in below mentioned article for appreciating modern Power CPU utilization behavior,

    Understanding Processor Utilization on Power Systems - AIX!/wiki/Not+AIX/page/Understanding+Processor+Utilization+on+Power+Systems+-+AIX


    Hope this helps !



    • R2R4_Ivan_NG
      2 Posts

      Re: How to interpert and link the CPU_ALL, CPU_SUMM and PCPU_ALL tags?

      ‏2013-07-15T08:44:41Z  in response to MrBhatt

      Mr Bhatt, It helps a lot. Thanks for your explanation.