Confusing CPU Utilisation ?

[rveri]

Hi all ,

We have 4 CPU in the system L2000-36 . And recently getting 100% cpu usage many times.

While watching top and sar output found this as follows:


-------------
CPU Status:


TOP shows

274 processes: 254 sleeping, 20 running
Cpu states:
CPU LOAD USER NICE SYS IDLE BLOCK SWAIT INTR SSYS
0 0.09 2.0% 0.0% 1.2% 96.8% 0.0% 0.0% 0.0% 0.0%
1 0.57 5.6% 0.0% 1.8% 92.6% 0.0% 0.0% 0.0% 0.0%
2 0.28 14.9% 0.0% 0.6% 84.5% 0.0% 0.0% 0.0% 0.0%
3 0.85 5.8% 0.0% 4.0% 90.3% 0.0% 0.0% 0.0% 0.0%
--- ---- ----- ----- ----- ----- ----- ----- ----- -----
avg 0.45 7.0% 0.0% 1.8% 91.2% 0.0% 0.0% 0.0% 0.0%

---------------------------------------------------------------------



But at the same time sar shows this :

# sar -u -M 4 9

HP-UX sapsys0 B.11.11 U 9000/800 11/30/05

18:30:02 cpu %usr %sys %wio %idle
18:30:06 0 0 1 0 98
1 7 2 91 0
2 3 1 96 0
3 6 4 3 87
system 4 2 47 46
18:30:10 0 1 5 1 92
1 1 3 96 0
2 6 2 92 0
3 6 6 0 88
system 3 4 47 45
----------------------------------------------------------

& this

# sar -u 5 7

HP-UX sapsys0 B.11.11 U 9000/800 11/30/05

18:33:27 %usr %sys %wio %idle
18:33:32 1 1 49 48
18:33:37 6 3 46 46
18:33:42 0 1 50 49
18:33:47 2 2 47 49
18:33:52 1 1 49 49
18:33:57 22 3 35 40
18:34:02 4 2 47 47

Average 5 2 46 47
----------------------------------------------------------


Question:
Top shows 91% IDLE CPU , where as sar shows 47% (including cpu 1 and cpu 2, 100% used always). ??

Please suggest, why this difference is. And what to do , to get exact details.

Thanks.

[Raj D.]

Hi ,

sar result seems to be more correct than top.

hth,
Raj.

[Eric SAUBIGNAC]

Hi rveri

as far as i know, HP-UX is the only unix system which gives %wio metric with sar. top and glance don't show this value.


U should not consider this metric as CPU consumer. The definition for %wio is "idle with some process waiting for I/O (only block I/O, raw I/O, or VM pageins/swapins indicated)".

So if U want to compare top and glance idle CPU, U should first add %wio & %idle from sar to compare to IDLE from top.

Now, high %wio could mean that you have some stress with your disks, due to swapping activity or heavy application load. So have a look at "sar -d", "vmstat -S" ...

Hope this will help

Eric

(PBFWME;-)