topas and mpstat disagree on CPU count

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aix, lpar, mpstat, performance tuning, topas

 
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# 1  
Old 01-10-2012
topas and mpstat disagree on CPU count

I have a number of LPARs on one P520. All LPARs are running 5.3 and I observe the following:

On some LPARs the number of CPUs found do not match between topas and mpstat.

Server 1:
Code:
$ mpstat

System configuration: lcpu=4 ent=0.2 mode=Uncapped

cpu  min  maj  mpc  int   cs  ics   rq  mig lpa sysc us sy wt id   pc  %ec  lcs
  0 3236207143 10334920 18148 3129232930 4185678899 2113273478    1 52924493 100 367388385328 53 45  0  1 0.02  8.0 1128243307
  1 603958753 5039979 16124 1524069311 1859429164 970562064    0 41186584 100 222067273272 49 49  0  2 0.01  4.9 68661856
  2 1710507793 3119307 4364 1114068729 1623216950 830873642    3 34012743 100 206322132851 48 50  0  1 0.01  4.8 1775110222
  3 250548546 2479568 3764 1040035340 1334942079 712336992    0 23302581 100 159082003333 48 50  0  1 0.01  3.5 1588140807
  U    -    -    -    -    -    -    -    -   -    -  -  -  3 76 0.16 78.8    -
ALL 5801222235 20973774 42400 6807406310 9003267092 4627046176    4 151426401 100 954859794784 11 10  3 76 0.04 21.2 4560156192

Code:
$ topas -c 4 -i 2

Topas Monitor for host:    anker-prod           EVENTS/QUEUES    FILE/TTY
Wed Jan 11 00:07:56 2012   Interval: 2         Cswitch    1404  Readch  1191.2K
                                                Syscall   81019  Writech 1592.3K
CPU  User%  Kern%  Wait%  Idle%  Physc          Reads      7208  Rawin         0
0     71.4   27.3    0.1    1.2   0.51          Writes     9568  Ttyout      448
1     64.4   28.9    0.0    6.6   0.05          Forks         1  Igets         0
2      0.0   36.3    0.0   63.7   0.00          Execs         1  Namei       499
                                                Runqueue    0.3  Dirblk        0

Topas only shows 3 CPUs where mpstat shows 4 CPUs.


On Server2 both commands agree on the number of CPUs
Code:
$ mpstat

System configuration: lcpu=4 ent=0.2 mode=Uncapped

cpu  min  maj  mpc  int   cs  ics   rq  mig lpa sysc us sy wt id   pc  %ec  lcs
  0 9860614934 2732104 7298 6735808867 9419381532 4702171407    3 4684492 100 65615358106 32 57  0 10 0.01  3.0 418549046
  1 1973963245 223280 2636 859857037 781266777 458989902    0 12072469 100 21592902586 34 44  0 22 0.00  0.4 1140935784
  2 67906433 112022 2726 251438391 16705237 8752709    0 124434 100 498800985 17 39  0 44 0.00  0.0 253852298
  3 2206185 58927 2548 246896346 5519713 2819540    0 183719 100 23307562  4 36  0 60 0.00  0.0 247932362
  U    -    -    -    -    -    -    -    -   -    -  -  -  0 96 0.19 96.5    -
ALL 11904690797 3126333 15208 8094000641 10222873259 5172733558    3 17065114 100 87730369239  1  2  0 97 0.01  3.5 2061269490

Code:
$ topas -c 4 -i 2
Topas Monitor for host:    kamstra-test         EVENTS/QUEUES    FILE/TTY
Wed Jan 11 00:11:15 2012   Interval:  2         Cswitch     211  Readch   223.7K
                                                Syscall    1226  Writech    3298
CPU  User%  Kern%  Wait%  Idle%  Physc          Reads       109  Rawin         1
0     12.4   74.1    0.1   13.4   0.01          Writes        9  Ttyout     1207
1      0.0   34.1    0.0   65.9   0.00          Forks         1  Igets         0
2      0.0   43.0    0.0   57.0   0.00          Execs         1  Namei       263
3      0.0   43.5    0.0   56.5   0.00          Runqueue    1.5  Dirblk        0

Both LPARs are configured on the same P520.

I hope someone can explain to me why the commands do not match up on some LPARs.

Greetings,
Peter
# 2  
Old 01-11-2012
Just guessing now, could this be caused by dynamic CPU folding?
In this case the effect would not be visible all the time and more likely
occur on LPARs with low or volatile load...

Greetings,
Greg

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