>the detailed MVS capture ratio discussions imply that MVS isn't even bothering 
>to do the clock accounting for large parts of the kernel (and in some cases 
>has been as high as 60%).

A long time ago, in a lab far far away, IBM made a (possibly erroneous) 
decision when CPU was expensive to not measure everything. The rough guideline, 
so I was told was it took 4-8000 instructions to measure an event. So, anything 
under 20K was not worth it (again, I'm quoting what I was told from [old] 
memory).
Also, at the time, no console activity measured (ie: operator commands).
Some things changed when SMF Typ30-6 waw introduced (System Address Spaces).
-
-teD

300,000 Kilometres per Second
Not only is it a good idea!
It's the LAW!!!    

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