Bug 174619

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User-Agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.7.12) Gecko/20050921 Red Hat/1.7.12-1.4.1

Description of problem:
When I use a particular option to the 'top' command, specifically, -b -n1, I do not get the proper output. 

When running top in regular mode, it keeps updating and the values on the Cpu(s) line changes with each update. However, when running top with the -bn1 switches (batch mode, 1 iteration), the Cpu(s) line does not change from run to run over seconds, minutes or even hours.

Here is an example of top, with no switches:

top - 13:42:52 up 21 days,  7:36, 38 users,  load average: 0.93, 0.86, 0.70
Tasks: 289 total,   3 running, 286 sleeping,   0 stopped,   0 zombie
Cpu(s): 15.9% us,  7.9% sy,  0.0% ni, 75.5% id,  0.2% wa,  0.5% hi,  0.0% si
Mem:   2074936k total,  1677308k used,   397628k free,    75060k buffers
Swap:  2064376k total,    53180k used,  2011196k free,   989352k cached

In another widow, close to the same time, I ran 'top -bn1':

top - 13:42:54 up 21 days,  7:36, 38 users,  load average: 0.93, 0.86, 0.70
Tasks: 292 total,   2 running, 290 sleeping,   0 stopped,   0 zombie
Cpu(s): 36.9% us,  2.3% sy,  0.0% ni, 50.3% id, 10.4% wa,  0.1% hi,  0.0% si
Mem:   2074936k total,  1678076k used,   396860k free,    75064k buffers
Swap:  2064376k total,    53180k used,  2011196k free,   989348k cached

Notice that most of the values on the Cpu(s) line are not even close. Any that are seem to be a concidence. This is especially true with 'id' which represents the percentage of time the CPU is idle.

I've been monitoring a number of RH 7.2, RHEL3, and RHEL4 systems. Only the RHEL4 systems have this problem.

On one RHEL4 system, about 50.3% id has been showing consistently for each check of top -bn1 run every 5 minutes. For another RHEL4 system, the id% has been constant at about 81%.

Version-Release number of selected component (if applicable):
procps-3.2.3-8.2

How reproducible:
Always

Steps to Reproduce:
1. Open one window, run 'top'
2. Open another window, run 'watch -n3 "top -bn1|head -7"'
3.
  

Actual Results:  The window running 'top' with no parameters works normally, values for Cpu(s) change almost every update.

The window running top -bn1 repeatedly via 'watch' clearly demonstrates the problem. The values for the Cpu(s) line don't change.

The unchanging values from tob -bn1 can be very different from normal top.

Expected Results:  top -bn1 should return approximately the same result as top when run at the same time.

Additional info:

This appears to be an initialization problem with top. 

When I first start top, without parameters, the first putput shows the exact same values as the 'watch -n3 "top -bn1|head -7"'. On the next update of normal/interactive mode top, the Cpu(s) values change, drastically, and then continue to change with each update.

It seems top on RHEL4 initially gives a false or (counter based?) value for Cpu(s). If it takes an additional cycle to determine and provide real values, batch mode should be fixed so that proper values are reported.