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frequent update_cpu_power messages in the system logs

This document (7015325) is provided subject to the disclaimer at the end of this document.

Environment

SUSE Linux Enterprise Server 11 Service Pack 1 (SLES 11 SP1)
SUSE Linux Enterprise Server 11 Service Pack 2 (SLES 11 SP2)

Situation


Log messages relating to update_cpu_power appear frequently in the system logs:

Jun  6 13:17:12 myhost kernel: [87824625.772466] update_cpu_power: cpu_power = 28614818560; scale_rt = 49748003745
Jun  6 13:17:12 myhost kernel: [51795828.865150] update_cpu_power: cpu_power = 24528796992; scale_rt = 42644292225
Jun  6 13:17:12 myhost kernel: [87824626.024221] update_cpu_power: cpu_power = 21251351804; scale_rt = 36946323002
Jun  6 13:17:12 myhost kernel: [87824626.036207] update_cpu_power: cpu_power = 20892174701; scale_rt = 36321879278
Jun  6 13:17:14 myhost kernel: [87824627.762462] update_cpu_power: cpu_power = 28542184816; scale_rt = 49621727084

These messages may have non-consecutive timestamps.

In the example above, it can be seen that the timestamps from the kernel are not
all consecutive.

Jun  6 13:17:12 myhost kernel: [87824625.772466]
Jun  6 13:17:12 myhost kernel: [51795828.865150]
Jun  6 13:17:12 myhost kernel: [87824626.024221]





Resolution

Update to SLES 11 SP3 or later, which is not effected by this issue.

SLES 11 SP2 is not effected by the issue, however a patch has been provided as a
precautionary measure in kernel-3.0.101-0.7.19.1, which is available to customers with
Long Term Service Pack Support (LTSS).

Customers who have LTSS for SLES 11 SP1 can update to kernel-2.6.32.59-0.13.1 or later.

Cold booting the system at a minimum of every 208 days should avoid the issue.

Additional Information

Additional checks were put in place to protect scale_rt_power() from clock
aberrations, and also to prevent any anomalous value returned by scale_rt_power()
from being stored in load balancing structures to be encountered at some later time.

As a safety measure was implemented to avoid potential overflows in the clocksource.

Also, changes were made to limit the number of update_cpu_power messages that would
be logged.

Disclaimer

This Support Knowledgebase provides a valuable tool for NetIQ/Novell/SUSE customers and parties interested in our products and solutions to acquire information, ideas and learn from one another. Materials are provided for informational, personal or non-commercial use within your organization and are presented "AS IS" WITHOUT WARRANTY OF ANY KIND.

  • Document ID:7015325
  • Creation Date:03-JUL-14
  • Modified Date:07-JUL-14
    • SUSESUSE Linux Enterprise Server

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