Description

VCPUs added to running domains on SPARC T7, S7 and M7 Systems (added using commands such as 'ldm add-vcpu') may have less than 20% of the performance of originally assigned VCPUs.

Occurrence

This issue can occur on the following platforms:

SPARC Platform

• SPARC T7-1 with Firmware version 9.7.1.c (patch 23291631) or earlier
• SPARC T7-2 with Firmware version 9.7.1.c (patch 23291632) or earlier
• SPARC T7-4 with Firmware version 9.7.1.c (patch 23291633) or earlier
• SPARC M7-8 with Firmware version 9.7.1.b (patch 23291634) or earlier
• SPARC M7-16 with Firmware version 9.7.1.b patch 23291634) or earlier
• SPARC S7-2 with Firmware version 9.7.2.c (patch 23632951) or earlier
• SPARC S7-2L with Firmware version 9.7.2.c (patch 23632952) or earlier
• SPARC Netra S7-2 with Firmware version 9.7.2.c (patch 23632954) earlier

To determine the firmware version installed on the system, use the following ILOM command:

    -> show /HOST sysfw_version

Symptoms

If the described issue occurs, computations on the domain may not complete as quickly as expected. Because only the newly added VCPUs are affected, it may not be noticed, or noticed as erratic performance issues.

To check a system for affected VCPUs, a simple performance test can be run.

For example, this shell script will allow detection of slower VCPUs:

    #!/bin/sh

    CMD="dd if=/dev/random of=/dev/null bs=8 count=51200"
    CPUS=`psrinfo | cut -f1` 
    for i in $CPUS ; do
        echo $i "\c"
        pbind -b $i $$ >/dev/null
        sh -c "time -p $CMD" 2>&1 | grep real
        done

The output on a relatively unloaded server should look similar to the following:

    0 real     0.2
    1 real     0.2
    2 real     0.3
    3 real     0.4
    4 real     0.2
    ...

Affected VCPUs will show significantly higher values:

    32 real   1.3

Workaround

To work around this issue, disable power management, then, if required, re-enable.

To disable power management, do the following:

On the T7 and S7 Platforms:

    -> set /SP/powermgmt policy=disabled

On the M7 Platform:

    -> set /Servers/PDomains/PDomain_[0-3]/SP/powermgmt policy=disabled

Resolution

This issue is addressed on the following platforms:

SPARC Platform

• SPARC T7-1 with Firmware version 9.7.3.b (patch 24483620) or later
• SPARC T7-2 with Firmware version 9.7.3.b (patch 24483621) or later
• SPARC T7-4 with Firmware version 9.7.3.b (patch 24483622) or later
• SPARC M7-8 with Firmware version 9.7.3.b (patch 24483623) or later
• SPARC M7-16 with Firmware version 9.7.3.b patch 24483623) or later
• SPARC S7-2 with Firmware version 9.7.3.b (patch 24483624) or later
• SPARC S7-2L with Firmware version 9.7.3.b (patch 24483625) or later
• SPARC Netra S7-2 with Firmware version 9.7.3.b (patch 24483627) or later

Patches

<patch 24483620>
<patch 24483621>
<patch 24483622>
<patch 24483623>
<patch 24483624>
<patch 24483625>
<patch 24483627>

History

11-Aug-2016: Document released, status Workaround
19-Oct-2016: Updated the Resolution section. State Resolved

Questions regarding this document should be addressed to
sunalertpublication_us_grp@oracle.com and copy the
submitter/responsible engineer listed below.

Internal Contributor/Submitter: Grant.Gredvig@oracle.com
Internal Eng Responsible Engineer: Grant.Gredvig@oracle.com
Oracle Knowledge Analyst: jeff.folla@oracle.com
Internal Eng Business Unit Group: Systems RPE
Internal Associated SR IDs: 3-12980266561, 3-12336468195, 3-12002190951, 3-12288296901
Internal Pending Patches:
Internal Resolution Patches:

References

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