Power

NMON TOP data does not report a process using a CPU at a 100% if it is CPU bound, as you (and I) would expect, but instead adjusts the usage down based on relative usage of available logical processors. This "AIX adjustment" is depending on SMT level, POWER CPU generation and, potentially even clock frequency.
What I typically do is to run a quick "CPU eater" and document wat TOP reports as CPU usage for that known CPU constrained process. Then I use that number to normalize all NMON TOP CPU utilization percentages accordingly.
I use the following "CPU eater" as my test (ksh)
let a=1
while [ 1 ]; do
let a=a+1
done

Below the results when I did this testing in my lab (note that you want to verify those numbers for your specific environment as AIX adjustments may have changed since then!)

NMON TOP data does not report a process using a CPU at a 100% if it is CPU bound, as you (and I) would expect, but instead adjusts the usage down based on relative usage of available logical processors. This "AIX adjustment" is depending on SMT level, POWER CPU generation and, potentially even clock frequency.
What I typically do is to run a quick "CPU eater" and document wat TOP reports as CPU usage for that known CPU constrained process. Then I use that number to normalize all NMON TOP CPU utilization percentages accordingly.
I use the following "CPU eater" as my test (ksh)
let a=1
while [ 1 ]; do
let a=a+1
done

Below the results when I did this testing in my lab (note that you want to verify those numbers for your specific environment as AIX adjustments may have changed since then!)

This is very good information - thank you for sharing it! 

Would you happen to have the original IBM slide deck or reference doc that you could attach or link to?  I've done some looking for the IBM source and am coming up empty.

Thanks!

NMON TOP data does not report a process using a CPU at a 100% if it is CPU bound, as you (and I) would expect, but instead adjusts the usage down based on relative usage of available logical processors. This "AIX adjustment" is depending on SMT level, POWER CPU generation and, potentially even clock frequency.
What I typically do is to run a quick "CPU eater" and document wat TOP reports as CPU usage for that known CPU constrained process. Then I use that number to normalize all NMON TOP CPU utilization percentages accordingly.
I use the following "CPU eater" as my test (ksh)
let a=1
while [ 1 ]; do
let a=a+1
done

Below the results when I did this testing in my lab (note that you want to verify those numbers for your specific environment as AIX adjustments may have changed since then!)

Craig,

I did this work internally - not sure there is "official IBM documentation" spelling it out like the slides do. (By the way, I'm with IBM)

The slides are in an "Oracle on AIX Best Practices" presentation I did for virtual TechU in 2022. FYI, I'll be re-doing those presentations, refreshed/updated, on 5/2 and 5/9 and material will be shared after the calls.

See Power VUG WEB site for further details:  https://www.ibm.com/support/pages/power-virtual-user-group

Ralf.

This is very good information - thank you for sharing it! 

Would you happen to have the original IBM slide deck or reference doc that you could attach or link to?  I've done some looking for the IBM source and am coming up empty.

Thanks!

NMON TOP data does not report a process using a CPU at a 100% if it is CPU bound, as you (and I) would expect, but instead adjusts the usage down based on relative usage of available logical processors. This "AIX adjustment" is depending on SMT level, POWER CPU generation and, potentially even clock frequency.
What I typically do is to run a quick "CPU eater" and document wat TOP reports as CPU usage for that known CPU constrained process. Then I use that number to normalize all NMON TOP CPU utilization percentages accordingly.
I use the following "CPU eater" as my test (ksh)
let a=1
while [ 1 ]; do
let a=a+1
done

Below the results when I did this testing in my lab (note that you want to verify those numbers for your specific environment as AIX adjustments may have changed since then!)