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Thread: Weird process..

  1. #1
    Join Date
    Oct 2011
    Beans
    40

    Post Weird process..

    Hi there people , i was wondering if anyone would have any idea of which process causes this .
    Code:
     
        8 root      20   0       0      0      0 R  0.0  0.0   0:00.25 rcuos/0    9 root      20   0       0      0      0 S  0.0  0.0   0:00.00 rcuos/1
       10 root      20   0       0      0      0 S  0.0  0.0   0:00.00 rcuos/2
       11 root      20   0       0      0      0 S  0.0  0.0   0:00.00 rcuos/3
       12 root      20   0       0      0      0 S  0.0  0.0   0:00.00 rcuos/4
       13 root      20   0       0      0      0 S  0.0  0.0   0:00.00 rcuos/5
       14 root      20   0       0      0      0 S  0.0  0.0   0:00.00 rcuos/6
       15 root      20   0       0      0      0 S  0.0  0.0   0:00.00 rcuos/7
       16 root      20   0       0      0      0 S  0.0  0.0   0:00.00 rcuos/8
       17 root      20   0       0      0      0 S  0.0  0.0   0:00.00 rcuos/9
       18 root      20   0       0      0      0 S  0.0  0.0   0:00.00 rcuos/10
       19 root      20   0       0      0      0 S  0.0  0.0   0:00.00 rcuos/11
       20 root      20   0       0      0      0 S  0.0  0.0   0:00.00 rcuos/12
       21 root      20   0       0      0      0 S  0.0  0.0   0:00.00 rcuos/13
       22 root      20   0       0      0      0 S  0.0  0.0   0:00.00 rcuos/14
       23 root      20   0       0      0      0 S  0.0  0.0   0:00.00 rcuos/15
       24 root      20   0       0      0      0 S  0.0  0.0   0:00.00 rcuos/16
       25 root      20   0       0      0      0 S  0.0  0.0   0:00.00 rcuos/17
       26 root      20   0       0      0      0 S  0.0  0.0   0:00.00 rcuos/18
       27 root      20   0       0      0      0 S  0.0  0.0   0:00.00 rcuos/19
       28 root      20   0       0      0      0 S  0.0  0.0   0:00.00 rcuos/20
       29 root      20   0       0      0      0 S  0.0  0.0   0:00.00 rcuos/21
       30 root      20   0       0      0      0 S  0.0  0.0   0:00.00 rcuos/22
       31 root      20   0       0      0      0 S  0.0  0.0   0:00.00 rcuos/23
       32 root      20   0       0      0      0 S  0.0  0.0   0:00.00 rcuos/24
       33 root      20   0       0      0      0 S  0.0  0.0   0:00.00 rcuos/25   
       73 root      20   0       0      0      0 S  0.0  0.0   0:00.00 rcuob/0
       74 root      20   0       0      0      0 S  0.0  0.0   0:00.00 rcuob/1
       75 root      20   0       0      0      0 S  0.0  0.0   0:00.00 rcuob/2
       76 root      20   0       0      0      0 S  0.0  0.0   0:00.00 rcuob/3
       77 root      20   0       0      0      0 S  0.0  0.0   0:00.00 rcuob/4
       78 root      20   0       0      0      0 S  0.0  0.0   0:00.00 rcuob/5
       79 root      20   0       0      0      0 S  0.0  0.0   0:00.00 rcuob/6
       80 root      20   0       0      0      0 S  0.0  0.0   0:00.00 rcuob/7
       81 root      20   0       0      0      0 S  0.0  0.0   0:00.00 rcuob/8
       82 root      20   0       0      0      0 S  0.0  0.0   0:00.00 rcuob/9
       83 root      20   0       0      0      0 S  0.0  0.0   0:00.00 rcuob/10
       84 root      20   0       0      0      0 S  0.0  0.0   0:00.00 rcuob/11
       85 root      20   0       0      0      0 S  0.0  0.0   0:00.00 rcuob/12
       86 root      20   0       0      0      0 S  0.0  0.0   0:00.00 rcuob/13
       87 root      20   0       0      0      0 S  0.0  0.0   0:00.00 rcuob/14
       88 root      20   0       0      0      0 S  0.0  0.0   0:00.00 rcuob/15
       89 root      20   0       0      0      0 S  0.0  0.0   0:00.00 rcuob/16
       90 root      20   0       0      0      0 S  0.0  0.0   0:00.00 rcuob/17
       91 root      20   0       0      0      0 S  0.0  0.0   0:00.00 rcuob/18
       92 root      20   0       0      0      0 S  0.0  0.0   0:00.00 rcuob/19
       93 root      20   0       0      0      0 S  0.0  0.0   0:00.00 rcuob/20
       94 root      20   0       0      0      0 S  0.0  0.0   0:00.00 rcuob/21
       95 root      20   0       0      0      0 S  0.0  0.0   0:00.00 rcuob/22
       96 root      20   0       0      0      0 S  0.0  0.0   0:00.00 rcuob/23
       97 root      20   0       0      0      0 S  0.0  0.0   0:00.00 rcuob/24
       98 root      20   0       0      0      0 S  0.0  0.0   0:00.00 rcuob/25
       99 root      20   0       0      0      0 S  0.0  0.0   0:00.00 rcuob/26
      100 root      20   0       0      0      0 S  0.0  0.0   0:00.00 rcuob/27
      101 root      20   0       0      0      0 S  0.0  0.0   0:00.00 rcuob/28
      102 root      20   0       0      0      0 S  0.0  0.0   0:00.00 rcuob/29
    Following Ubuntu since 7.10 Feisty Fawn

  2. #2
    Join Date
    Feb 2009
    Location
    Dallas, TX
    Beans
    7,796
    Distro
    Ubuntu 16.04 Xenial Xerus

    Re: Weird process..

    Hi enterdavertex.

    Those processes are the result of turning on the following kernel flags:
    Code:
    CONFIG_RCU_NOCB_CPU
    CONFIG_RCU_NOCB_CPU_ALL
    CONFIG_RCU_STALL_COMMON
    CONFIG_RCU_USER_QS
    They were set on by default starting from saucy (13.10) (reference here).

    As far as the reason, I can only speculate that it was done to reduce OS jitter.

    Hope it helps. Let us know how it goes.
    Regards.

  3. #3
    Join Date
    Oct 2011
    Beans
    40

    Re: Weird process..

    Thanks papibe for your explanation !
    Following Ubuntu since 7.10 Feisty Fawn

  4. #4
    Join Date
    Sep 2014
    Beans
    1

    Re: Weird process..

    We have run into this same issue. What is odd, on vmware 5.1, there is a single process for both rcuos and rcuob. On xenserver 6.1, there are 14 processes and on Hyper-V 2012 R2 there are 63 processes each for rcuos and rcuob! Does anyone know why the differences based on hypervisor?

    I know they are all sleeping, but it seems excessive.

  5. #5
    Join Date
    Sep 2014
    Beans
    2

    Re: Weird process..

    Hi Papibe,
    Can you please explain below flags more? Why these are generating lots of rcuob process? If I disabled these flags then what is the impact on my OS or kernel?
    CONFIG_RCU_NOCB_CPU
    CONFIG_RCU_NOCB_CPU_ALL
    CONFIG_RCU_STALL_COMMON
    CONFIG_RCU_USER_QS

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