11/28/95, 4FAX# 2703
 
  High CPU Percentage for kproc Process 514/516
 
 
 
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  ABOUT THIS DOCUMENT
 
       This document explains why the CPU percentage reported for
|      kproc process 514 (on AIX 3.2) and kproc process 516 (on AIX
|      4.1) may have increased.  Please note that the high per-
       centage for this process is normal.  Since this process just
       indicates the idle time of the system, the high percentage
       does not indicate a problem and no action is required.
 
       This document applies to AIX 3.2 and 4.1.
 
  EXPLANATION OF HIGH CPU PERCENTAGE
 
|      Note:  If you are running AIX 4.1, substitute process 514
|      with process 516 in the documentation below.
 
       You may have seen the CPU% greatly increase for process 514,
       the wait kernel process, which is executed only when no
       other process is runnable.  Here is an explanation:
 
       The change in CPU% occurred when the start times were fixed
       for a few of the processes (514, 771, and 1028).  This fix
       was in APAR IX33330.  Prior to the fix, the start time for
       these processes was 0 (which translated to Dec 31, 1969)
       rather than the true start time.  Since the startTime(pid)
       was an extremely small number (0) and the currentTime is
       always an extremely large number (> 700,000,000), the CPU%
       for the 514 process was kept artificially low.
 
       The formula for computing the CPU% is:
 
       CPU% = CPUTime(pid) / (currentTime - startTime(pid) ) *
       100.0
 
       Now that the start time has been corrected, the above
       equation will give the true percentage of CPU that the
       process has consumed over its lifetime.  On unburdened
       systems, process 514 will use 50% or more of CPU.  Since
       this computation is based on lifetime statistics, it will be
       slow to rise and slow to fall.
 
       Additionally, you should see that adding the numbers in %CPU
       column will not yield 100%.  For example, process A may have
 
                        High CPU Percentage for kproc Process 514/516  1
 
 
                                                    11/28/95, 4FAX# 2703
 
       been using 80% of the CPU for its first hour.  Then process
       B is started at a higher priority and consumes 80%.  Process
       A still runs, but now only gets 5% of the CPU slices.  The
       %CPU as shown by "ps ug" will gradually decline for process
       A, starting from 80% and eventually leveling off near 5%.
       For a while,  both process A and B will show %CPU of 80%.
 
       To determine if you have the start time fix in place, enter
       the following command:
 
          ps -fu root | grep 514
 
       If the 5th field is "Dec 31", you do NOT have the fix.
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
                        High CPU Percentage for kproc Process 514/516  2
 
 
                                                    11/28/95, 4FAX# 2703
 
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  END OF DOCUMENT (kproc.high.cpu.lxp, 4FAX# 2703)
 
 
 
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