SUMMARY: load average wrong?

From: Granzow, Doug (NCI) <granzowd_at_mail.nih.gov>
Date: Thu Mar 07 2002 - 09:10:14 EST
Thanks to all who responded -- too many responses to list names.

The overwhelming response was that you need to divide the load average by
the number of CPUs to make a comparison.  A 12 processor box with a load
average of 5 is about as busy as a 1 processor box with a load average of
5/12 or 0.42.

To me that doesn't match the definition of load average given in uptime(1)
which says it is "the average number of jobs in the run queue over the last
1, 5 and 15 minutes."  If there were an average of 5 jobs in the run queue,
wouldn't vmstat show 5, or at least some non-zero value, in the run queue
column?  I am going to guess that the difference is that the "load average"
computation used by w, uptime, and top includes processes that are
*currently* running, where vmstat only reports on processes that are
*waiting* to run.  In my stats, vmstat shows 0 in the run queue column -- no
processes waiting to run.  But looking at the idle column seems to support
that about half of the 12 CPUs are busy at any given instant, i.e. there are
about 6 running processes at any given instant.  So if the load average
includes these running processes, that would support a load average of about
6.

Thanks again for all of your responses!

Doug




-----Original Message-----
From: Granzow, Doug (NCI) 
Sent: Wednesday, March 06, 2002 3:25 PM
To: 'sunmanagers@sunmanagers.org'
Subject: load average wrong?


I suspect the load average on a Sunfire 6800 is wrong.  It is reporting load
averages around 5.00 even though all 12 of the CPUs are partially idle.
vmstat shows r = 0.  What could be causing the load average to be high, or
how can I get an accurate report of the load average?  (w, uptime, and top
all report the same load average)

bash-2.03# uname -a
SunOS hostname 5.8 Generic_108528-10 sun4u sparc SUNW,Sun-Fire
bash-2.03# uptime
  3:17pm  up 21 day(s),  1:31,  4 users,  load average: 5.18, 5.01, 5.11
bash-2.03# vmstat 5
 procs     memory            page            disk          faults      cpu
 r b w   swap  free  re  mf pi po fr de sr m1 m1 m1 m2   in   sy   cs us sy
id
 23 0 0 21384600 10314952 0 0 0 0  0  0  0  2  1  1  0 4294967196 0 0 -59 -2
-43
 0 0 0 21508048 10822144 125 76 979 0 0 0 0 0  0  0  0 4586 249126 2693 45 6
49
 0 0 0 21507664 10817944 119 15 947 0 0 0 0 0  0  0  0 4573 250649 2655 45 6
50
 0 0 0 21506864 10813520 119 49 960 0 0 0 0 0  0  0  0 4575 249904 2671 44 6
50
 0 0 0 21505792 10809008 109 22 854 0 0 0 0 0  0  0  0 4558 249775 2623 44 8
48
 0 0 0 21510992 10811360 112 552 816 0 0 0 0 0 0  0  0 4470 250176 2397 43 6
51
 0 0 0 21511248 10808792 71 29 596 0 0 0 0  0  0  0  0 4347 250057 2008 44 6
50
 0 0 0 21511240 10806576 69 15 596 0 0 0 0  0  0  0  0 4338 252180 1988 43 6
50
^C
bash-2.03# mpstat 5
CPU minf mjf xcal  intr ithr  csw icsw migr smtx  srw syscl  usr sys  wt idl
 12   34   0 1242   614  499   51   25   10    4    0   426   57   2   0  42
 13   35   0  190   325  292   52   26   10    5    0   596   57   2   0  41
 14   36   0  184   325  295   51   26   10    5    0   661   57   2   0  41
 15   35   0  190   328  297   51   26   10    5    0   693   57   2   0  41
 16   35   0  178   325  290   51   26   10    5    0   552   57   2   0  42
 17   35   0  186   325  288   51   26   10    5    0   534   57   2   0  42
 18   35   0  181   325  291   52   26   10    5    0   696   57   2   0  41
 19   35   0  187   325  290   53   26   10    5    0   568   57   2   0  41
 20   35   0  187   325  288   54   26   10    5    0   516   57   2   0  41
 21   34   0  197   353  315   51   25   10    6    0   540   57   2   0  41
 22   35   0  197   349  313   51   26   10    5    0   673   57   2   0  42
 23   35   0  180   325  286   52   26   10    4    0   554   57   2   0  42
CPU minf mjf xcal  intr ithr  csw icsw migr smtx  srw syscl  usr sys  wt idl
 12    0  15 3860   611  500  393   15   25   28    0   220   39   2   0  59
 13    0   3  132   309  298   52    9    8    8    0 161359   47  34   0
19
 14    0   2   95   310  298   55   10   12    9    0 35515   65  12   0  23
 15   26   6  217   312  297  142   12   16   20    0 51534   54  11   0  35
 16    1   5  243   310  291   92   10   15   22    0   233   58   1   0  40
 17   16  15  546   314  293  325   13   21   34    0   312   38   2   0  60
 18    0   9  453   313  294  308   13   20   29    0   244   46   2   0  52
 19    0   6  179   312  294  108   12   19   15    0   209   51   1   0  47
 20    0  13  622   312  293  417   12   19   49    0   439   29   3   0  68
 21    0  15  634   924  911  313   12   16  116    0   366   24   2   0  75
 22    0  10  473   319  300  263   13   20   33    0   248   39   1   0  60
 23    0  13  345   314  294  177   14   23   29    0   329   41   1   0  58
CPU minf mjf xcal  intr ithr  csw icsw migr smtx  srw syscl  usr sys  wt idl
 12    0   7 3734   606  500  130   10   16   31    0 33540   41   8   0  52
 13   13  12  348   312  292  314   12   20   22    0   197   36   3   0  61
 14    0   4  134   309  294   74    9   16   11    0  1126   63   1   0  36
 15    0   5  130   312  295   75   11   13   18    0 69333   56  14   0  30
 16    0   7  262   310  289  100   11   15   24    0 42551   44  11   0  45
 17    0  10  247   307  291  113    7   15   18    0   192   34   8   0  58
 18    0   6  173   311  291   81   11   14   13    0 18969   56   5   0  39
 19    0   6  167   309  289   82    9   15   15    0   974   60   2   0  38
 20    1   8  561   310  289  138   10   17   42    0   381   49   2   0  49
 21    0  17  813   874  862 1095   30   23   64    0  1206   12   3   0  85
 22    0   9  319   317  299  120   11   15   20    0 69102   44  15   0  42
 23    0   7  458   314  291  173   14   20   41    0 12015   39   5   0  56
CPU minf mjf xcal  intr ithr  csw icsw migr smtx  srw syscl  usr sys  wt idl
 12    0  16 3964   611  500  224   15   21   48    0  1675   30   2   0  68
 13    0  10  289   309  295   99    9   16   22    0   736   47   2   0  51
 14   13   6  154   312  297   91   12   19   12    0   204   59   2   0  39
 15    0   6  150   313  296   93   12   16   12    0 42861   63   8   0  29
 16    0  10  426   311  294  128   11   19   29    0  5135   47   2   0  51
 17    0   6  156   307  293   78    7   13   11    0   137   46   4   0  50
 18    0   4  236   310  294   95   10   15   18    0  5281   56   1   0  43
 19    0  12  495   315  294  435   15   23   32    0   314   36   2   0  62
 20    0  13  502   310  293  370   10   17   40    0   530   39   2   0  59
 21    0  16  869   922  911  805   21   17   89    0   565   15   2   0  83
 22    0   8  328   318  302  177   11   12   11    0 141415   44  27   0
29
 23    0   5  211   310  295   82   10   13   13    0 52874   51  13   0  36
^C
bash-2.03# uptime
  3:18pm  up 21 day(s),  1:32,  4 users,  load average: 5.62, 5.18, 5.16


Will summarize.  Thanks in advance,
Doug
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Received on Thu Mar 7 08:11:12 2002

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