ITEM: G9927

My system is cpu bound. Which process is causing the problem?

Question:

My system is running 100% CPU bound, how can I tell which process is
causing the problem?

Response:

'tprof' is the best tool to use to analyze a CPU bottleneck.  It is one of the
AIX specific performance tools and can be found in /usr/lpp/bosperf.  If the
suite of AIX Specific Performance tools is not installed on your system,
install bosext1 (BOS Extended Commands 1).

Syntax AIX 3.2.4 or below:
        tprof -p sleep -x sleep 30
        pg __sleep.all

AIX 3.2.5 or greater:
        tprof -x sleep 30
        pg __prof.all

The first section of the output file lists the processes in descending order of
CPU usage.  The second section combines process with like names and, again,
sorts by CPU usage.  

To run tprof on AIX Levels prior to AIX 3.2.5, you must also have bos.adt
(BOS Application Development Toolkit) installed.

On AIX 3.2.5, tprof may show an incorrect process name for PID 514, the wait
process.  Tprof may also report an incorrect PID for processes that have been
exec'ed from other applications (You might see an 8 digit PID).  There are two
APARs against tprof on AIX 3.2.5: IX41401 and IX41692.

If you cannot run tprof, you can get similar CPU usage information from the
first section of a 'netpmon' report.  Netpmon is another of the AIX specific
performance tools that can be found in /usr/lpp/bosperf. 

Syntax: netpmon -Ocpu -ooutfile ; sleep 30 ; trcstop
        pg outfile

Occasionally someone may recommend using the 'ps' command to determine which
process(es) are consuming CPU resources.  Ps reports %CPU as the sum of user
and system CPU execution time, divided by the elapsed time (since the process
started executing), multiplied by 100.  For example, if process A starts
executing now, and is 100% CPU bound for one minute, at the end of the minute
'ps' will show %CPU as 100.  If process A then goes to sleep and process B
starts executing 100% CPU bound for a minute, at the end of the second minute,
process A will show %CPU as 50 and process B will show %CPU as 100.  As
you can see, just looking at this information can be misleading if you do not
consider the start time (STIME) of the process.



Support Line: My system is cpu bound.  Which process is causing the problem? ITEM: G9927

Dated: February 1994 Category: N/A

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