CPU Activity

The CPU Activity section reports on logical core and logical processor activity. For each processor, the report provides a set of calculations that are provided at a particular granularity that depends on whether multithreading is disabled (LOADxx PROCVIEW CPU parameter is in effect) or enabled (LOADxx PROCVIEW CORE parameter is in effect).

If multithreading is disabled for a processor type, all calculations are at logical processor granularity.

If multithreading is enabled for a processor type, some calculations are provided at logical core granularity and some are provided at logical processor (thread) granularity. The CPU Activity section displays exactly one report line per thread showing all calculations at logical processor granularity. Those calculations that are provided at core granularity are only shown in the same report line that shows the core id in the CPU NUM field and which is representing the first thread of a core.

The following calculations are on a per logical processor basis when multithreading is disabled and on a per logical core basis when multithreading is enabled:

Percentage of the interval time the processor was online
LPAR view of the processor utilization (LPAR Busy time percentage)
Percentage of a physical processor the logical processor is entitled to use
Multithreading core productivity (only reported when multithreading is enabled)
Multithreading core utilization (only reported when multithreading is enabled)

The following calculations are on a per logical processor basis regardless whether multithreading is enabled or disabled:

MVS view of the processor utilization (MVS Busy time percentage)
Percentage of the online time the processor was parked (in HiperDispatch mode only)
I/O interrupts rate (general purpose processors only)
Percentage of I/O interrupts handled by the I/O supervisor without re-enabling (general purpose processors only)

If RMF is running as a guest under z/VM® and Monitor I Session option NOVMGUEST is active, it only reports the MVS busy time percentage. If you want to measure partition utilization (as well as the individual CPU utilization of the single guests, namely LPAR busy time percentage), you need to use a z/VM monitor. Performance analysts need both views of CPU utilization. The MVS view is a direct indicator to see a CPU bottleneck, while the LPAR view is important with respect to capacity aspects.

The LPAR view of the CPU utilization takes the different states that are possible into account:

WAIT state
NON WAIT state being dispatched by PR/SM
NON WAIT state not being dispatched by PR/SM
WAIT state being dispatched when the LPAR has dedicated processors

The LPAR Busy time is calculated depending on the status of the logical processor:

Dedicated and LOADxx PROCVIEW CPU is in effect or hardware does not support multithreading: CPU time = Online time - Wait time
Dedicated and LOADxx PROCVIEW CORE is in effect on hardware that supports multithreading: CPU time = MT Core LPAR Busy time
Wait completion = YES (requires multithreading disabled): CPU time = Dispatch time - Wait time
Wait completion = NO: CPU time = Dispatch time

The LPAR view of CPU utilization is calculated as:

                     CPU time
LPAR Busy Time(%) = ----------- * 100
                    Online time

The MVS view of the CPU utilization considers the following states:

CPU wait state
CPU busy state (which means NON WAIT state)

In HiperDispatch mode, logical processors can be parked and are not dispatched by z/OS. The MVS BUSY fields in the RMF report reflect the effective used capacity for the logical processors and the entire logical partition. The values are based on the difference between online time and MVS wait time to provide an operating system perspective of busy time. Parked processors in HiperDispatch mode generally reflect unavailable capacity at high physical processor utilizations. The formula for MVS Busy has been changed with HiperDispatch mode to exclude the parked time to show how busy the logical processor was when not parked.

HiperDispatch = NO: Time range = Online time
HiperDispatch = YES: Time range = Online time - Parked time

Note: In HiperDispatch mode, the Total/Average MVS BUSY TIME % does not consider parked processors. Therefore, do not use Total/Average LPAR BUSY TIME % and Total/Average MVS BUSY TIME % to calculate the MVS to LPAR busy ratio.

The MVS view of CPU utilization is:

                   Time range - Wait time
MVS Busy Time(%) = ---------------------- * 100
                        Time range

If multithreading is enabled for at least one processor type, you can use the multithreading core productivity and multithreading core utilization metrics to determine the effectiveness of the configured logical cores.

When the multithreading core productivity (MT % PROD) equals 100% in multithreading mode, all threads on the core are executing work and all core resources are being used. If MT % PROD is less than 100%, the core resources were dispatched to physical hardware but one or more threads on a core were in a wait because they had no work to run.

If multithreading is enabled, the available core capacity can be calculated using the multithreading core utilization and LOG PROC SHARE %:

Available Core Capacity = LOG PROC SHARE % - MT % UTIL