AIX 5L Problem Determination - IBM Redbooks

The syncd, X, and dtsession are all processes that have been active since IPL;
that is why they have accumulated more total TIME than the test program.
The %CPU column
The %CPU column, generated by the -u or -v flag, shows the percentage of time
that the process has used the CPU since the process started. The value is
computed by dividing the time the process uses the CPU by the elapsed time of
the process. In a multi-processor environment, the value is further divided by the
number of available CPUs, since several threads in the same process can run on
different CPUs at the same time. Because the time base over which this data is
computed varies, the sum of all %CPU fields can exceed 100 percent. In the
following example, there are two ways to sort the extracted output from a system.
The first example includes kprocs, for example, PID 516, which is a wait process.
The other, more complex command syntax excludes such kprocs:
# ps auxwww |head -n 5
USER PID %CPU %MEM SZ RSS TTY STAT STIME TIME COMMAND
root 18802 25.0 1.0 4140 4160 pts/11 A 15:40:28 5:44 ./tctestprog
root 516 25.0 5.0 8 15136 - A Jun 15 17246:34 kproc
root 774 20.6 5.0 8 15136 - A Jun 15 14210:30 kproc
root 1290 5.9 5.0 8 15136 - A Jun 15 4077:38 kproc
# ps gu|head -n1; ps gu|egrep -v "CPU|kproc"|sort +2b -3 -n -r |head -n 5
USER PID %CPU %MEM SZ RSS TTY STAT STIME TIME COMMAND
root 18802 25.0 1.0 4140 4160 pts/11 A 15:40:28 7:11
./tctestprog
imnadm 12900 0.0 0.0 264 332 - A Jun 15 0:00 /usr/IMNSearch/ht
root 0 0.0 5.0 12 15140 - A Jun 15 4:11 swapper
root 1 0.0 0.0 692 764 - A Jun 15 0:28 /etc/init
root 3398 0.0 1.0 1692 2032 - A Jun 15 1:48 /usr/dt/bin/dtses
From the output, you can see that the test program, tctestprog, uses about 25
percent of available CPU resources since the process started.
Upon finding a run-away process, the next step in the analysis is to find out what
exactly in the process uses the CPU. For this, a profiler is needed. The AIX
profiler of preference is tprof.
10.1.4 The tprof command
The tprof command can be used for application tuning and for information
collection of overall CPU utilization. The tprof command can be run over a time
period to trace the activity of the CPU.
In the AIX operating system, an interrupt occurs periodically to allow a
housekeeping kernel routine to run. This occurs 100 times per second. When the
tprof command is invoked, it counts every such kernel interrupt as a tick. This
Chapter 10. Performance problem determination 243