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Hi all,

someone knows why i get 16 LCPUs in many performance tools when i only
have 8 physical CPUs in my box ?

DATA: POWER5, AIX53ML2

# mpstat 3

System configuration: lcpu=16

cpu min maj mpc int cs ics rq mig lpa sysc us sy wa id pc
0 0 0 0 7423 15066 7607 0 28 100 91 0 15 0 85 0.78
1 0 0 0 11 0 0 0 0 - 0 0 0 0 100 0.22
2 51 9 0 319 3235 2860 0 29 100 1870 9 2 6 84 0.70
3 0 0 0 15 0 0 0 0 - 0 0 0 0 100 0.29
4 0 0 0 47 1506 925 0 98 96 1300 11 3 0 86 0.73
5 0 0 0 12 0 0 0 0 - 0 0 0 0 100 0.27
6 221 0 0 51 3013 2747 0 92 91 2879 15 1 0 83 0.73
7 0 0 0 14 0 0 0 0 - 0 0 0 0 100 0.27
8 0 0 0 75 1451 726 0 2 100 771 92 5 0 3 0.07
9 0 0 0 136 1 1 0 0 100 12901 97 3 0 0 0.93
10 0 0 0 34 14446 7366 0 4 100 865 1 9 0 90 0.71
11 0 0 0 25 11 6 0 0 100 15 0 0 0 100 0.30
12 0 0 0 175 12812 6757 0 1 100 16 0 4 0 96 0.68
13 0 0 0 18 6 3 0 1 91 754 2 3 0 94 0.32
14 0 0 0 24 3288 1644 0 0 100 117 68 13 0 19 0.03
15 0 0 0 134 1 1 0 0 100 13271 97 3 0 0 0.97
ALL 272 9 0 8513 54836 30643 0 255 100 34850 28 4 1 68 8.01
--------------------------------------------------------------------------------


# lsdev -C | grep proc
proc0 Disponible 00-00 Procesador
proc2 Disponible 00-02 Procesador
proc4 Disponible 00-04 Procesador
proc6 Disponible 00-06 Procesador
proc8 Disponible 00-08 Procesador
proc10 Disponible 00-10 Procesador
proc12 Disponible 00-12 Procesador
proc14 Disponible 00-14 Procesador


thanks

jhidalgo wrote:
> Hi all,
>
> someone knows why i get 16 LCPUs in many performance tools when i only
> have 8 physical CPUs in my box ?

<snip>

You have a p5 machine running AIX 5.3 which therefore supports
Simultaneous Multithreading (SMT), which uses additional registers on
the chip to make a single CPU look like two to the OS. Understanding the
performance you're getting needs a little more understanding than in a
non-SMT environment but it's worth it - for about 10% more transistors
you can get up to 30% better performance.

FOr further information, go to http://www.redbooks.ibm.com and look at
"AIX 5L Differences Guide Version 5.3 Edition" - in particular the
chapter on Performance Monitoring.