Forum - System performance degradation with fan control script problem

NEC has found that a system performance degradation may occur with the fan control script problem due to a known bash bug(*1). Users will eventually need to install the bug fixed version of bash from Redhat. Until the fix, please think about the workaround below.

Condition

• OS : RHEL/CentOS 8
  • RHEL 8.1

bash 4.4.19-1.el8_1 to 4.4.19-11.el8_1

• RHEL 8.2

bash 4.4.19-1.el8_2 to 4.4.19-11.el8_2

• CentOS 8

bash 4.4.19-1 to 4.4.19-14

How to check and do workaround

• Please check if cpu usage is high for the nec-ve-fan-ctl service on the vector host.

$ top -b -n 1 | grep "nec-ve-"

123456 root　　　 20　 0　 123696　　9968　　1452 S　　0.2　0.0　12:26.96 nec-ve-fan-ctl.sh

　　　　　　　　　　　　　　　　　　　　　　　　　　  ^^^^(*2)

123457 root　　　 20 　0　 123696　　9976　　1452 S　　0.1　0.0 　0:37.34 nec-ve-fan-ctl-mon.sh

　　　　　　　　　　　　　　　　　　　　　　　　　　  ^^^^(*2)

＊ the script names (nec-ve-fan-ctl) may be displayed a bit differently, depending on your environment.

• In the normal operation the cpu usage for them stays 0-1%. When this issue is occuring the cpu usage will be close to 100% (*2). Please restart nec-ve-fan-ctl services in root user then.

# systemctl restart nec-ve-fan-ctl-mon nec-ve-fan-ctl

References

^*1: bash-4.4.19 bug: Bash loops forever trying to reap children, spins on the CPU
external link) https://bugzilla.redhat.com/show_bug.cgi?id=1943495