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#Power
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  • 1.  minimum capacity

    Posted Wed December 01, 2010 03:26 PM

    Originally posted by: tech100


    the vmstat shows:

    
    kthr    memory              page              faults              cpu ----- ----------- ------------------------ ------------ ----------------------- r  b   avm   fre  re  pi  po  fr   sr  cy  in   sy  cs us sy id wa    pc    ec 1  0 382037 477519   0   0   0   0    0   0  16  241 348  0  0 99  0  0.01   0.7 1  0 382037 477519   0   0   0   0    0   0  20  226 370  0  0 99  0  0.01   0.6 1  0 382036 477520   0   0   0   0    0   0  19  320 404  0  0 99  0  0.01   0.8 1  0 382036 477520   0   0   0   0    0   0  17  207 340  0  0 99  0  0.01   0.6 1  0 382030 477526   0   0   0   0    0   0  17  569 357  0  0 97  2  0.01   0.7 1  0 382128 477428   0   0   0   0    0   0  45 12332 493 10  5 83  1  0.16  15.7 0  0 382034 477522   0   0   0   0    0   0  17  205 404  0  0 99  0  0.01   0.8
    


    and lparstat:

    
    Type                                       : Shared Mode                                       : Uncapped Entitled Capacity                          : 1.00 Partition Group-ID                         : 32772 Shared Pool ID                             : 0 Online Virtual CPUs                        : 4 Maximum Virtual CPUs                       : 4 Minimum Virtual CPUs                       : 1 Online Memory                              : 6784 MB Maximum Memory                             : 10240 MB Minimum Memory                             : 6144 MB Variable Capacity Weight                   : 128 Minimum Capacity                           : 1.00 Maximum Capacity                           : 4.00 Capacity Increment                         : 0.01 Maximum Physical CPUs in system            : 4 Active Physical CPUs in system             : 4 Active CPUs in Pool                        : 4 Shared Physical CPUs in system             : 4 Maximum Capacity of Pool                   : 400 Entitled Capacity of Pool                  : 400 Unallocated Capacity                       : 0.00 Physical CPU Percentage                    : 25.00% Unallocated Weight                         : 0 Desired Virtual CPUs                       : 4 Desired Memory                             : 6784 MB Desired Variable Capacity Weight           : 128 Desired Capacity                           : 1.00
    

    Doesn't the "Minimum Capacity : 1" mean that the LPAR should have 1 processing unit all the time? If not what does it mean?

    I am curious why vmstat shows pc=0.01 nearly all the time - I know the system is not heavy loaded but I thought having minimum processing set to 1.0, the pc in vmstat should never be lower than 1.0...

    btw. what is the latency in dynamical/automatic processing units chnages (increase/decrease) by a hypervizor?

    does xmtopas process make some role in such processing unit increase/decrease operations?
    #AIX-Forum


  • 2.  Re: minimum capacity

    Posted Wed December 01, 2010 05:25 PM

    Originally posted by: The_Doctor


    I'm sure there are many interpretations of Minimum Capacity, but in simplistic terms, my interpretation is --> Minimum Capacity is the MINIMUM amount of CPU allotment that must be available in the PHYSICAL FRAME, otherwise the LPAR will not start.

    Personally, I think you are confusing Minimum Capacity with Entitled Capacity. They are significantly different. Entitled Capacity (EC) is the CPU allocation that you are guaranteed to get during each time slice. So, with EC = 1.0 you are guaranteed to get 1.0 CPUs worth of processing during each time slice BUT ONLY IF YOU NEED IT. Excess/unused cycles are generally ceded back to the hypervisor for potential distribution to other needy LPARs.

    PC shows you what is physically consumed during the interval. So, PC = 0.01 indicates an average of 1% of 1 CPU was used during that interval. A PC = 3.45 would indicate an average of 3 CPUs at 100% + 1 CPU at 45% for a total average consumption of 345% during the interval.

    The hypervisor recalculates changes every 10ms or 100 times per second (aka a time slice). What you're guaranteed in terms of EC does not change. Once an LPAR is powered on and the hypervisor sets the EC, the EC stays at that value until you change it (either forcibly thru the use of DLPAR or similar changes thru the profile, which would require a POWER OFF/ON cycle). I therefore do not understand where any latency would come into play..... but maybe I'm missing your point.

    You also wrote > does xmtopas process make some role in such processing unit increase/decrease operations? I think it's safe to speculate & say the answer is --> NO !
    #AIX-Forum


  • 3.  Re: minimum capacity

    Posted Thu December 02, 2010 02:50 AM

    Originally posted by: tech100


    thank you very much for your valuable post.
    #AIX-Forum


  • 4.  Re: minimum capacity

    Posted Thu December 02, 2010 03:16 AM

    Originally posted by: tech100


    by the way - could you please also explain what means on lparstat output:

    Physical CPU Percentage :25.00%
    #AIX-Forum


  • 5.  Re: minimum capacity

    Posted Thu December 02, 2010 12:10 PM

    Originally posted by: The_Doctor


    
    Physical CPU Percentage :25.00%
    


    Well, Physical CPU Percentage = Entitled Capacity / Online Virtual CPUs, so in your case 1.0 / 4 = 25%

    If EC = 3.0 & Online Virtual CPUs = 3 then 3.0 / 3 = 100%

    If EC = 4.0 & Online Virtual CPUs = 8 then 4.0 / 8 = 50%
    That's pretty much it....

    If needed, man lparstat may help you to understand this further.
    #AIX-Forum