LPAR - not using all processors - Aix

This is a discussion on LPAR - not using all processors - Aix ; I have two LPARS, both running Oracle for the same application (one is Test, the other is Development). Each has two processors assigned, and because they're dual-core, they show up in NMON as four processors. On one LPAR, it uses ...

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Thread: LPAR - not using all processors

  1. LPAR - not using all processors

    I have two LPARS, both running Oracle for the same application (one is
    Test, the other is Development). Each has two processors assigned,
    and because they're dual-core, they show up in NMON as four
    processors. On one LPAR, it uses all four processors equally. On the
    other, it appears to only be using two of the processors (the other
    two show 100% idle all the time). I've never seen that behavior
    before, either from an LPAR of a physical box. What might cause that?

  2. Re: LPAR - not using all processors

    rodak schrieb:
    > I have two LPARS, both running Oracle for the same application (one is
    > Test, the other is Development). Each has two processors assigned,
    > and because they're dual-core, they show up in NMON as four
    > processors. On one LPAR, it uses all four processors equally. On the
    > other, it appears to only be using two of the processors (the other
    > two show 100% idle all the time). I've never seen that behavior
    > before, either from an LPAR of a physical box. What might cause that?

    Dual-core will not make 4 out of 2.... this is SMT.
    It seems on that 2nd LPAR you don't have enough load
    to use that 2nd thread on the two CPUs, so they stay
    idle.

  3. Re: LPAR - not using all processors


    There would seem to be plenty of load on the system - processors 0 and
    1 are running 80-100% busy, while processors 2 and 3 are dead-idle.
    What would cause that?

    On Aug 28, 1:15*am, Thomas Braunbeck
    wrote:
    > rodak schrieb:> I have two LPARS, both running Oracle for the same application (one is
    > > Test, the other is Development). *Each has two processors assigned,
    > > and because they're dual-core, they show up in NMON as four
    > > processors. *On one LPAR, it uses all four processors equally. *On the
    > > other, it appears to only be using two of the processors (the other
    > > two show 100% idle all the time). *I've never seen that behavior
    > > before, either from an LPAR of a physical box. *What might cause that?

    >
    > Dual-core will not make 4 out of 2.... this is SMT.
    > It seems on that 2nd LPAR you don't have enough load
    > to use that 2nd thread on the two CPUs, so they stay
    > idle.



  4. Re: LPAR - not using all processors

    >
    > output of "lparstat -i" on the two lpars in question would be helpful.

    First is the one that uses all four processors more or less equally:

    Node Name : HQDBLAW2
    Partition Name : HQDBLAW2
    Partition Number : 5
    Type : Shared-SMT
    Mode : Capped
    Entitled Capacity : 2.00
    Partition Group-ID : 32773
    Shared Pool ID : 0
    Online Virtual CPUs : 2
    Maximum Virtual CPUs : 2
    Minimum Virtual CPUs : 2
    Online Memory : 4096 MB
    Maximum Memory : 8192 MB
    Minimum Memory : 2048 MB
    Variable Capacity Weight : 0
    Minimum Capacity : 2.00
    Maximum Capacity : 2.00
    Capacity Increment : 0.01
    Maximum Physical CPUs in system : 32
    Active Physical CPUs in system : 16
    Active CPUs in Pool : 16
    Unallocated Capacity : 0.00
    Physical CPU Percentage : 100.00%
    Unallocated Weight : 0

    Sample NMON output:
    nmon 2=Top-Child-CPU Host=HQDBLAW2 Refresh=2 secs
    14:22.37
    CPU-Utilisation-Small-View EntitledCPU= 2.00 UsedCPU=
    1.162
    Logical CPUs
    0----------25-----------50----------75----------100
    CPU User% Sys% Wait% Idle%| | |
    | |
    0 19.9 13.9 2.0 64.2|UUUUUUUUUssssss
    > |

    1 13.9 20.4 0.5 65.2|UUUUUUssssssssss
    > |

    2 10.0 23.9 1.5 64.7|UUUUsssssssssss
    > |

    3 25.9 30.8 1.0 42.3|UUUUUUUUUUUUsssssssssssssss
    > |

    EntitleCapacity/VirtualCPU
    +-----------|------------|-----------|------------+
    EC 24.4 23.1 0.2 10.5|
    UUUUUUUUUUUUsssssssssssiiiii---------------------|
    VP 24.4 23.1 0.2 10.5|
    UUUUUUUUUUUUsssssssssssiiiii---------------------|
    EC= 58.1% VP= 58.1% +--Capped---|------------|-----------100%
    VP=2 CPU+


    Next is the one that only seems to want to use two of the processors:

    Node Name : HQDBLAW3
    Partition Name : HQDBLAW3
    Partition Number : 3
    Type : Shared-SMT
    Mode : Capped
    Entitled Capacity : 2.00
    Partition Group-ID : 32771
    Shared Pool ID : 0
    Online Virtual CPUs : 2
    Maximum Virtual CPUs : 2
    Minimum Virtual CPUs : 2
    Online Memory : 4096 MB
    Maximum Memory : 8192 MB
    Minimum Memory : 2048 MB
    Variable Capacity Weight : 0
    Minimum Capacity : 2.00
    Maximum Capacity : 2.00
    Capacity Increment : 0.01
    Maximum Physical CPUs in system : 32
    Active Physical CPUs in system : 16
    Active CPUs in Pool : 16
    Unallocated Capacity : 0.00
    Physical CPU Percentage : 100.00%
    Unallocated Weight : 0

    sample NMON output, while three DB report jobs are running:
    CPU-Utilisation-Small-View EntitledCPU= 2.00 UsedCPU=
    0.649
    Logical CPUs
    0----------25-----------50----------75----------100
    CPU User% Sys% Wait% Idle%| | |
    | |
    0 34.0 19.0 9.5 37.5|
    UUUUUUUUUUUUUUUUUsssssssssWWWW> |
    1 18.5 8.0 4.0 69.5|UUUUUUUUUssssWW
    > |

    2 0.0 0.0 0.0 100.0|
    > |

    3 0.0 0.0 0.0 100.0|
    > |

    EntitleCapacity/VirtualCPU
    +-----------|------------|-----------|------------+
    EC 21.4 7.2 0.4 3.4|
    UUUUUUUUUUsssi-----------------------------------|
    VP 21.4 7.2 0.4 3.4|
    UUUUUUUUUUsssi-----------------------------------|
    EC= 32.4% VP= 32.4% +--Capped---|------------|-----------100%
    VP=2 CPU+

  5. Re: LPAR - not using all processors

    rodak wrote:
    >> output of "lparstat -i" on the two lpars in question would be helpful.

    > First is the one that uses all four processors more or less equally:
    >
    > Node Name : HQDBLAW2
    > Partition Name : HQDBLAW2
    > Partition Number : 5
    > Type : Shared-SMT
    > Mode : Capped
    > Entitled Capacity : 2.00
    > Partition Group-ID : 32773
    > Shared Pool ID : 0
    > Online Virtual CPUs : 2
    > Maximum Virtual CPUs : 2
    > Minimum Virtual CPUs : 2
    > Online Memory : 4096 MB
    > Maximum Memory : 8192 MB
    > Minimum Memory : 2048 MB
    > Variable Capacity Weight : 0
    > Minimum Capacity : 2.00
    > Maximum Capacity : 2.00
    > Capacity Increment : 0.01
    > Maximum Physical CPUs in system : 32
    > Active Physical CPUs in system : 16
    > Active CPUs in Pool : 16
    > Unallocated Capacity : 0.00
    > Physical CPU Percentage : 100.00%
    > Unallocated Weight : 0
    >
    > Sample NMON output:
    > nmon 2=Top-Child-CPU Host=HQDBLAW2 Refresh=2 secs
    > 14:22.37
    > CPU-Utilisation-Small-View EntitledCPU= 2.00 UsedCPU=
    > 1.162
    > Logical CPUs
    > 0----------25-----------50----------75----------100
    > CPU User% Sys% Wait% Idle%| | |
    > | |
    > 0 19.9 13.9 2.0 64.2|UUUUUUUUUssssss
    >> |

    > 1 13.9 20.4 0.5 65.2|UUUUUUssssssssss
    >> |

    > 2 10.0 23.9 1.5 64.7|UUUUsssssssssss
    >> |

    > 3 25.9 30.8 1.0 42.3|UUUUUUUUUUUUsssssssssssssss
    >> |

    > EntitleCapacity/VirtualCPU
    > +-----------|------------|-----------|------------+
    > EC 24.4 23.1 0.2 10.5|
    > UUUUUUUUUUUUsssssssssssiiiii---------------------|
    > VP 24.4 23.1 0.2 10.5|
    > UUUUUUUUUUUUsssssssssssiiiii---------------------|
    > EC= 58.1% VP= 58.1% +--Capped---|------------|-----------100%
    > VP=2 CPU+
    >
    >
    > Next is the one that only seems to want to use two of the processors:
    >
    > Node Name : HQDBLAW3
    > Partition Name : HQDBLAW3
    > Partition Number : 3
    > Type : Shared-SMT
    > Mode : Capped
    > Entitled Capacity : 2.00
    > Partition Group-ID : 32771
    > Shared Pool ID : 0
    > Online Virtual CPUs : 2
    > Maximum Virtual CPUs : 2
    > Minimum Virtual CPUs : 2
    > Online Memory : 4096 MB
    > Maximum Memory : 8192 MB
    > Minimum Memory : 2048 MB
    > Variable Capacity Weight : 0
    > Minimum Capacity : 2.00
    > Maximum Capacity : 2.00
    > Capacity Increment : 0.01
    > Maximum Physical CPUs in system : 32
    > Active Physical CPUs in system : 16
    > Active CPUs in Pool : 16
    > Unallocated Capacity : 0.00
    > Physical CPU Percentage : 100.00%
    > Unallocated Weight : 0
    >
    > sample NMON output, while three DB report jobs are running:
    > CPU-Utilisation-Small-View EntitledCPU= 2.00 UsedCPU=
    > 0.649
    > Logical CPUs
    > 0----------25-----------50----------75----------100
    > CPU User% Sys% Wait% Idle%| | |
    > | |
    > 0 34.0 19.0 9.5 37.5|
    > UUUUUUUUUUUUUUUUUsssssssssWWWW> |
    > 1 18.5 8.0 4.0 69.5|UUUUUUUUUssssWW
    >> |

    > 2 0.0 0.0 0.0 100.0|
    >> |

    > 3 0.0 0.0 0.0 100.0|
    >> |

    > EntitleCapacity/VirtualCPU
    > +-----------|------------|-----------|------------+
    > EC 21.4 7.2 0.4 3.4|
    > UUUUUUUUUUsssi-----------------------------------|
    > VP 21.4 7.2 0.4 3.4|
    > UUUUUUUUUUsssi-----------------------------------|
    > EC= 32.4% VP= 32.4% +--Capped---|------------|-----------100%
    > VP=2 CPU+






    looks OK to me so far. Does "smtctl" output on the 2 lpars differ?
    Has oracle been configured identically? (not my field)

    Regards
    Joachim Gann

  6. Re: LPAR - not using all processors

    Yes, smtctl produces the same output on both:
    -------------------------------------------------------------------------------
    This system is SMT capable.
    SMT is currently enabled.
    SMT boot mode is not set.
    SMT threads are bound to the same virtual processor.

    proc0 has 2 SMT threads.
    Bind processor 0 is bound with proc0
    Bind processor 1 is bound with proc0

    proc2 has 2 SMT threads.
    Bind processor 2 is bound with proc2
    Bind processor 3 is bound with proc2
    -------------------------------------------------------------------------------

    I presume Oracle is configured identically - my DBA is pretty
    persnickety about such things.

    But maybe not - I just fired of a bunch of simple "find" commands, and
    saw from nmon that it did use all four processors. I've asked my DBA
    if there's something in Oracle that determines how it handlse multi-
    threaded processes.

    On Aug 28, 2:50*pm, Joachim Gann wrote:>
    > looks OK to me so far. Does "smtctl" output on the 2 lpars differ?
    > Has oracle been configured identically? (not my field)
    >
    > Regards
    > Joachim Gann



  7. Re: LPAR - not using all processors

    rodak schrieb:
    >> output of "lparstat -i" on the two lpars in question would be helpful.

    > First is the one that uses all four processors more or less equally:


    > CPU-Utilisation-Small-View
    > EntitledCPU= 2.00
    > UsedCPU= 1.162



    >
    > Next is the one that only seems to want to use two of the processors:
    >


    > CPU-Utilisation-Small-View
    > EntitledCPU= 2.00
    > UsedCPU= 0.649


    The 2nd system uses less than 1 CPU, so why should it touch the
    2nd CPU at all? Put sole load on that box (just a looping script
    will do) and see how the 2nd CPU starts 'working' when the UsedCPU
    value gets > 1

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