Hi Sebastien,
I have a question about how sar should operate during hotplug
operations. Consider the following situation:
1. offline a cpu
ita01 ~ # grep processor /proc/cpuinfo
processor : 0
processor : 1
processor : 2
processor : 3
ita01 ~ # echo 0 > /sys/devices/system/cpu/cpu3/online
ita01 ~ # grep processor /proc/cpuinfo
processor : 0
processor : 1
processor : 2
2. start sar
ita01 functional # sar -P ALL 1 0
Linux 2.6.19-rc1 (ita01) 10/06/06
ita01 functional # sar -P ALL 1 0
Linux 2.6.19-rc1 (ita01) 10/06/06
20:10:13 CPU %user %nice %system %iowait %steal %idle
20:10:14 all 20.45 0.00 2.26 0.00 0.00 77.29
20:10:14 0 3.98 0.00 2.39 0.00 0.00 93.63
20:10:14 1 47.41 0.00 2.39 0.00 0.00 50.20
20:10:14 2 9.96 0.00 1.99 0.00 0.00 88.05
...
3. online the cpu
ita01 ~ # echo 1 > /sys/devices/system/cpu/cpu3/online
4. The sar output does not display the newly onlined CPU, and
continues to only show cpu's 0, 1, and 2.
I'm wondering if this is intended behavior? When sar is started with
all the CPU's onlined, and a cpu is offlined when it runs, then it will
display 'nan' for that cpu, until it comes back online; this is fine,
since you can see in the output that a cpu is missing. However if the
cpu is brought online after sar starts, then the sar output is not
really providing complete information on the system. How do you think
sar ought to behave in this situation?
This is tested against sar 7.0.1, against the following platforms:
Itanium 2 64 ita01 4-proc Linux ia64 2.6.19-rc1 FAIL
AMD Opteron 64 amd01 2-proc Linux x86_64 2.6.19-rc1 FAIL
Intel Xeon 64 nfs13 2-proc Linux x86_64 2.6.19-rc1 FAIL
Thanks,
Bryce
