IBM Support

db_server or vobrpc_server processes on a Red Hat Enterprise Linux VOB server consume 100% CPU when using NAS storage for VOBs

Troubleshooting


Problem

This technote identifies a Linux® NFS defect within the Red Hat® Enterprise Linux (RHEL) kernel relating to a situation where either a db_server or vobrpc_server process consumes 100% of a CPU on a Red Hat Linux VOB server using NAS storage for the VOBs.

Symptom

db_server or vobrpc_server processes consume 100% of a CPU on a RedHat Linux VOB server when using NAS storage for the VOBs.

Cause


A defect with the Linux implementation of NFS was discovered.

Note: This only applies to clients with Red Hat Linux VOBs hosting VOB storage on a NAS device.

For the latest up to date information concerning this vendor defect, refer to technote 1315605 Clarification on the alert issued for RHEL 4 Update 5/6 and RHEL 5 and support for ClearCase VOB hosts with Network Attached VOB storage.

Diagnosing The Problem


The following behavior will be seen when running into this issue::

  1. A db_server or vobrpc_server process is consuming 100% of a CPU in a tight (user space) loop
    By a tight user space loop, we mean:
    1. the db_server or vobrpc_server process is consuming 100% CPU and
    2. the CPU it is using is in user mode not system mode. (See #2 below)

  2. You can check to see if you have the problem by running "top" and checking to see if a db_server or vobrpc_server process is consuming 100% of a CPU.
    You can also run the "sar" command - and check the heading %user in typical sar output such as:

    # sar -u 1 10
    Linux 2.6.9-55.EL (miami) 12/21/2007

    11:33:44 AM CPU %user  %nice %system %iowait %idle
    11:33:45 AM all 99.90  0.00  0.00    0.00    0.10
    11:33:46 AM all 100.00 0.00  0.00    0.00    0.00
    11:33:47 AM all 100.00 0.00  0.00    0.00    0.00
    11:33:48 AM all 99.99  0.00  0.00    0.00    0.01
    11:33:49 AM all 99.00  0.00  0.99    0.99    0.01
    11:33:50 AM all 100.00 0.00  0.00    0.00    0.00
    11:33:51 AM all 99.00  0.00  0.00    0.00    1.00
    11:33:52 AM all 100.00 0.00  0.00    0.00    0.00
    11:33:53 AM all 100.00 0.00  0.00    0.00    0.00
    11:33:54 AM all 99.99  0.00  0.00    0.00    0.01

Resolving The Problem

Refer to technote 1295636 Known issues with Linux VOB hosts accessing VOB storage on NAS over NFS for information about how to workaround the issue.

[{"Product":{"code":"SSSH27","label":"Rational ClearCase"},"Business Unit":{"code":"BU053","label":"Cloud & Data Platform"},"Component":"Operating System Configurations","Platform":[{"code":"PF016","label":"Linux"}],"Version":"7.0;7.0.0.1;7.0.0.2;7.0.0.3;7.0.0.4;7.0.0.5;7.0.0.6;7.0.1;7.0.1.1;7.0.1.2;7.0.1.3;7.0.1.4;7.0.1.5;7.1;7.1.0.1;7.1.0.2","Edition":"","Line of Business":{"code":"LOB36","label":"IBM Automation"}}]

Document Information

Modified date:
16 June 2018

UID

swg21292064