sar output shows different CPU utilization..

vikas027 · 07-15-2009, 10:23 PM

Hi All,

I am using RHEL 4

Code:

$ cat /etc/redhat-release
Red Hat Enterprise Linux ES release 4 (Nahant Update 4)

I have a issue with sar command. It is showing different idle CPU utilization, than showing in other commands like top, iostat, vmstat.

SAR OUTPUT where CPU idle state is 0 %

Code:

08:34:39 AM       CPU     %user     %nice   %system   %iowait     %idle
08:34:40 AM       all      0.00      0.00      0.00      0.00      0.00
08:34:41 AM       all      0.00      0.00      0.00    100.00      0.00
08:34:42 AM       all      0.00      0.00    100.00      0.00      0.00
08:34:43 AM       all      0.00      0.00      0.00    100.00      0.00
08:34:44 AM       all      0.00      0.00      0.00    100.00      0.00
08:34:45 AM       all      0.00      0.00      0.00    100.00      0.00
08:34:46 AM       all     14.29      0.00      0.00     85.71      0.00
08:34:47 AM       all      0.00      0.00      0.00    100.00      0.00
08:34:48 AM       all      0.00      0.00      0.00    100.00      0.00
08:34:49 AM       all      0.00      0.00     33.33     66.67      0.00
Average:          all      4.55      0.00      9.09     86.36      0.00

where as in other commands, it is showing CPU is above 84% idle.

Code:

$ vmstat
procs -----------memory---------- ---swap-- -----io---- --system-- ----cpu----
 r  b   swpd   free   buff  cache   si   so    bi    bo   in    cs us sy id wa
 0  0 101436  45524 137288 1562948    0    0     0     2    0     0 14  1 85  0
$
$ iostat | head -4 | tail -2
avg-cpu:  %user   %nice    %sys %iowait   %idle
          13.66    0.00    1.02    0.45   84.87
$
$ top -bn1 | grep -i cpu
Cpu(s): 13.7% us,  1.0% sy,  0.0% ni, 84.9% id,  0.4% wa,  0.0% hi,  0.0% si

Am I missing out something. There is nothing in /var/log/messages also, other than session opening/closing messages.

valen_tino · 07-16-2009, 09:18 AM

Is your output from the current sar report?

Can you post the output of:

Code:

# sar -u 5 60

and

Code:

# top -bn1 | grep -i cpu

I ran these two on my system and the %idle was identical along with vmstat and iostat

vikas027 · 07-16-2009, 10:58 PM

Yes, the output is different, this is my problem.

Ideally all commands should have the same CPU idle %.