Bug 579409

Description of problem:

The sysstat's programs such as mpstat shows one extra cpu.

According to the result of mpstat, the number of CPU is displayed from 0 to 8.
However, the number of CPU's core is actually 8, and it should be displayed
from 0 to 7. 

> # mpstat -P ALL 1
> 
> 16時49分08秒  CPU   %user   %nice    %sys %iowait    %irq   %soft  %steal   %idle    intr/s
> 16時49分09秒  all    0.00    0.00    0.12    0.12    0.00    0.00    0.00   99.75      6.00
> 16時49分09秒    0    0.00    0.00    0.00    1.00    0.00    0.00    0.00   99.00      0.00
> 16時49分09秒    1    0.00    0.00    0.00    0.00    0.00    0.00    0.00  100.00      0.00
> 16時49分09秒    2    0.00    0.00    0.00    0.00    0.99    0.00    0.00   99.01      1.00
> 16時49分09秒    3    0.00    0.00    0.00    0.00    0.00    0.00    0.00  100.00      1.00
> 16時49分09秒    4    0.00    0.00    0.00    0.00    0.00    0.00    0.00  100.00      0.00
> 16時49分09秒    5    0.00    0.00    0.00    0.00    0.00    0.00    0.00  100.00      2.00
> 16時49分09秒    6    0.00    0.00    0.00    0.00    0.00    0.00    0.00  100.00      0.00
> 16時49分09秒    7    0.00    0.00    0.99    0.00    0.00    0.00    0.00   99.01      2.00
> 16時49分09秒    8    0.00    0.00    0.00    0.00    0.00    0.00    0.00    0.00      0.00


Additional info:

In reviewing the source, when sysfs is mounted /sys, mpstat calculates the
number of CPU by counting "cpu*" under /sys/devices/system/cpu/.


The following in customer's environment.

> # find /sys/devices/system/cpu/ -maxdepth 1
> /sys/devices/system/cpu/
> /sys/devices/system/cpu/sched_mc_power_savings
> /sys/devices/system/cpu/cpuidle
> /sys/devices/system/cpu/cpu0
> /sys/devices/system/cpu/cpu1
> /sys/devices/system/cpu/cpu2
> /sys/devices/system/cpu/cpu3
> /sys/devices/system/cpu/cpu4
> /sys/devices/system/cpu/cpu5
> /sys/devices/system/cpu/cpu6
> /sys/devices/system/cpu/cpu7

I assume that "cpuidle" was considered with the 9th CPU by mistake.

The same phenomenon has been reported in the following issue:

 * https://bugzilla.redhat.com/show_bug.cgi?id=442801

Created attachment 412947 [details]
Patch adapted from BZ 442801 for sysstat 7.0.2

    Technical note added. If any revisions are required, please edit the "Technical Notes" field
    accordingly. All revisions will be proofread by the Engineering Content Services team.
    
    New Contents:
Previously, the mpstat utility wrongly interpreted data about processors in the system. Consequently, it reported a processor that did not exist. This bug has been fixed and non-existent CPUs are no longer reported by mpstat.

An advisory has been issued which should help the problem
described in this bug report. This report is therefore being
closed with a resolution of ERRATA. For more information
on therefore solution and/or where to find the updated files,
please follow the link below. You may reopen this bug report
if the solution does not work for you.

http://rhn.redhat.com/errata/RHSA-2011-1005.html