Applies To:

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sol13091: The global CPU usage ratio is always reported as 1 regardless of the CPU utilization
Known IssueKnown Issue

Original Publication Date: 09/13/2011
Updated Date: 01/07/2013

Description

The global CPU usage ratio is always reported as 1 regardless of the CPU utilization.

The global CPU usage ratio is an aggregated percentage of CPU utilization for the entire system calculated based on the CPU usage statistics, such as user, niced, idle, over the last 10-second interval. You can observe the global CPU usage ratio using the following methods:

  • Utilization % (last 10 sec) from the output of the tmsh show sys host-info global command
  • The sysGlobalHostCpuUsageRatio (.1.3.6.1.4.1.3375.2.1.1.2.20.13.0) SNMP variable

Impact

The BIG-IP system reports incorrect CPU utilization.

Symptoms

As a result of this issue, you may encounter the following symptoms:

  • The tmsh show sys host-info global command output reports 1 for the Total column in the Utilization % (last 10 sec) row on a loaded system.

    For example:

    Note: The following output is truncated for brevity purpose.

    CPU (clock ticks)              Last-5-second  Last-1-minute  Last-5-minute   Total
      -                            (Average/sec)  (Average/sec)  (Average/sec)       -

      Utilization % (last 10 sec)              -              -              -       1

  • The sysGlobalHostCpuUsageRatio SNMP variable reports 1 when you run an SNMP query on a loaded system.

    For example:

    snmpwalk -v2c -c public localhost sysGlobalHostCpuUsageRatio

    If you use the snmpwalk utility in the above example to query the variable on the BIG-IP system, the snmpwalk utility returns the following output:

    F5-BIGIP-SYSTEM-MIB::sysGlobalHostCpuUsageRatio.0 = Counter64: 1

Status

F5 Product Development has assigned ID 355208 to this issue, and has confirmed that this issue exists in the products listed in the Applies To box. For information about releases or hotfixes that resolve this issue, refer to the following table:

Type of Fix
Versions Fixed
Related Articles
Release 11.0.0 SOL2200: Most recent versions of F5 software
Hotfix None None

Workaround

To work around this issue, you can query for the sysGlobalHostCpuUsageRatio5s (.1.3.6.1.4.1.3375.2.1.1.2.20.21.0) SNMP variable, which is the global CPU usage ratio over 5 seconds. To do so, you can use the snmpwalk utility to query for the sysGlobalHostCpuUsageRatio5s variable by typing the following command from the command line:

Impact of workaround: The value reported is a calculated average over a 5-second interval instead of a 10-second interval.

snmpwalk -v2c -c public localhost sysGlobalHostCpuUsageRatio5s

Supplemental Information

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