Too many rcuob and rcuos are shown

Question

On my Linux server, Too many rcuob and rcuos process are shown.

Execute a following command.

ps auxwwf | grep rcu

And shown below.

root          9  0.0  0.0      0     0 ?        S     5月30   0:00  \_ [rcuob/0]
root         10  0.0  0.0      0     0 ?        S     5月30   0:00  \_ [rcuob/1]
:
:
root        151  0.0  0.0      0     0 ?        S     5月30   0:00  \_ [rcuob/142]
root        152  0.0  0.0      0     0 ?        S     5月30   0:00  \_ [rcuob/143]

and

root        154  0.0  0.0      0     0 ?        S     5月30   0:11  \_ [rcuos/0]
root        155  0.0  0.0      0     0 ?        S     5月30   0:04  \_ [rcuos/1]
:
:
root        296  0.0  0.0      0     0 ?        S     5月30   0:00  \_ [rcuos/142]
root        297  0.0  0.0      0     0 ?        S     5月30   0:00  \_ [rcuos/143]

The server's CPU is "Intel(R) Xeon(R) CPU E5-2630 v3 @ 2.40GHz"

Total Memory is "32GB"

and OS is"CentOS Linux release 7.2.1511 (Core)"

I do not know what these are, and if they are the problem, please let me know the procedure to fix it.

Not a problem - please see this question for an explanation: http://askubuntu.com/questions/523025/what-are-the-rcuos-rcuob-processes-im-seeing-in-top — davidm_uk, Sep 06 '16 at 14:12

score 1 · Answer 1 · answered Nov 29 '16 at 13:58

I noticed the same behaviour on RHEL7.2 3.10.0-327.el7. https://access.redhat.com/solutions/1404313 has the title More "rcuob" and "rcuos" kernel threads running than there are CPUs online, and describes how the RCU threads started did not match the number of online CPUs, but the number of possible CPUs. It explains a fix has been released with an errata RHSA-2016-2574, kernel 3.10.0-514.el7. I imagine CentOS will also have a fix.

To view the number of online CPUs and the number of possible CPUs:

> cd /sys/devices/system/cpu ; grep '' {online,offline,possible}
online:0-55
offline:56-191
possible:0-191

Count the number of rcuob and rcuos kernel threads:

> ps aux | awk '/\[(ksoftirqd|migration|watchdog|rcuo)/{print $11}' | sed 's/[0-9]//g' | sort | uniq -c
     56 [ksoftirqd/]
     56 [migration/]
    192 [rcuob/]
    192 [rcuos/]
     56 [watchdog/]

Too many rcuob and rcuos are shown

1 Answers1