RMF Meaning of "CPU Busy" and "CPU Wait"
From the point of view of z/OS running in a logical partition, CPU busy time is the sum of the durations of the periods during which the logical processor is actually executing instructions. For shared processor wait-disabled partitions, this is equal to the PR/SM dispatch time. For wait-enabled partitions, however, CPU busy time is equal to the dispatch time minus the CPU wait time recorded in the CPU Data section.
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From the point of view of z/OS running in a logical partition, CPU busy time is the sum of the durations of the periods during which the logical processor is actually executing instructions. For shared processor wait-disabled partitions, this is equal to the PR/SM dispatch time. For wait-enabled partitions, however, CPU busy time is equal to the dispatch time minus the CPU wait time recorded in the CPU Data section.
From the point of view of the entire complex, on the other hand, central processor utilization does not depend on the wait assist status. If a logical processor is dispatched, the central processor it uses is unavailable for other use, whether it is actually executing instructions or is in the wait state. The amount of time during which the central processor is unavailable to other partitions or for LPAR management functions is equal to the dispatch time in both cases. In order to differentiate this measurement from "CPU busy" as described previously, we can think of the dispatch time as "CPU allocation" time.
CPU wait time in the LPAR environment can be defined as "CPU not busy". This covers the amount of time represented by the difference between the overall duration of the measurement interval and CPU busy time. For wait-disabled partitions, this is the duration of the measurement interval minus the dispatch time. For wait-enabled partitions, this is the interval duration minus the difference between the dispatch time and the CPU wait time recorded in the CPU Data section.
The following formulas can be used to calculate processor utilization statistics:
- For partitions with dedicated processors:INTERVAL - WAITTIME PCT_BUSY = ------------------- x 100 INTERVAL PCT_ALLC = 100 (constant) WAITTIME PCT_WAIT = -------- x 100 INTERVAL PCT_NBSY = PCT_WAIT
- For partitions with shared processors and with wait-assist disabled:DISPTIME PCT_BUSY = -------- x 100 INTERVAL PCT_ALLC = PCT_BUSY PCT_WAIT = 0 (constant) INTERVAL - DISPTIME PCT_NBSY = ------------------- x 100 INTERVAL
- For partitions with shared processors and with wait-assist enabled:DISPTIME - WAITTIME PCT_BUSY = ------------------- x 100 INTERVAL DISPTIME PCT_ALLC = -------- x 100 INTERVAL WAITTIME PCT_WAIT = -------- x 100 INTERVAL INTERVAL - (DISPTIME - WAITTIME) PCT_NBSY = -------------------------------- x 100 INTERVALwhere:CA MICS label meaning element --------- --------------------------- -------- PCT_BUSY Percent processor busy IPUPCBS PCT_ALLC Percent processor allocated IPUPCDT PCT_WAIT Percent processor wait IPUPCVW PCT_NBSY Percent not using processor IPUPCWT INTERVAL Measurement interval DURATION WAITTIME processor wait time IPUWTM DISPTIME processor dispatch time IPUDTM