Could someone please explain...

[MethodMan1972]

....why on the same system, I get this output:-

# pmcycles -m
CPU 0 runs at 1648 MHz
CPU 1 runs at 1648 MHz
CPU 2 runs at 1648 MHz
CPU 3 runs at 1648 MHz
CPU 4 runs at 1648 MHz
CPU 5 runs at 1648 MHz
CPU 6 runs at 1648 MHz
CPU 7 runs at 1648 MHz

# lscfg | grep proc
+ proc0 Processor
+ proc2 Processor
+ proc4 Processor
+ proc6 Processor


....i.e., one output show's 8 procs, the other shows 4?

Is this a case of one Quad Core Proc not being enabled, and
one command shows it and the other doesn't?

Thanks

 

[p5wizard]

You have 4 CPUs, but on AIX 53 you have enabled SMT (Simultaneous multi threading), which makes one CPU core look like two (each CPU register is doubled, so each processor can handle two threads at a time).

For the OS and your apps, this looks like double number of processors.




HTH,

p5wizard

 

[MethodMan1972]

Thank you for the response. This was installed from CD using the default settings. How can I see this SMT Parameter is set and where can it be changed?

Thanks

 

[MethodMan1972]

...also, does this mean that the 4 Procs (Sounds like a 70's Soul Band) are in fact running at 3296 Mhz? And the SMT shows this as half this speed when enabled?

Thanks

 

[p5wizard]

smtctl gives info and can turn it on/off

lparstat will also give you info on it I think

All CPUs (and the SMT processors) run on tha same clock. 1.65 GHz on your server. With SMT on, you get a perf boost of 1.3 or so, but it depends on how much your app will profit from this multithreading.

CPU cycles wich would otherwise go to waste while data is read into one register set are used on the other register set...

google for "system p smt aix53" and read up on it.


HTH,

p5wizard

 

[khalidaaa]

Those proc0 to 8 are called logical CPUs (as p5wizard mentioned, they are enabled by the smt)

The other 4 that you listed from lscfg | grep proc are called virtual CPU. Those virtual CPUs are mapped into your physical ones!

I assume you are aware that with those 4 virtual CPUs you can access 4 physical CPUs per 1ms cycle concurrently as max (That's my undertanding from the course i attended)

The logical CPUs as what p5wizard said will boost your CPU performance by 30% approx. and they are best used with multithreaded applications.

Regards,
Khalid

 

[MethodMan1972]

Thanks again guys, this forum is great!

It looks like this is something for me to read up on, but thanks for pointing me in the right direction.