IBM Z9 Planning Manual page 164

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3-38
PR/SM Planning Guide
ZVSE
ZOSTEST
ZVM
v The share of processing resource for each online logical CP is calculated by
dividing the share for each LP by the number of online logical CPs. The share for
each logical CP is as follows:
ZVSE
ZOSTEST
ZVM
These percentages are used to determine preemption priority for I/O
interruptions. A lower priority logical CP can be preempted when an I/O
interruption is pending for a higher priority logical CP when the following occurs:
– The higher priority logical CP is further behind in its share, or
– The higher priority logical CP is not as far ahead of its share as the lower
priority logical CP.
For example, the lower priority LP is receiving 15% more than its processing
share, and the higher priority LP is receiving 10% more than its processing
share.
As long as there is excess CP capacity, processing weights have no effect on the
CP resources consumed. Weights affect processing when the number of logical
CPs that need processing time is greater than the number of physical CPs
available.
Processing Weights and Shared CP, ICF, IFA, IFL and zIIP Processors: Shared
general purpose, ICF, IFA, IFL and zIIP processors are each managed as separate
"pools" of physical resources. The processing weights assigned to logical partitions
using shared ICF, IFA, IFL, zIIP or general purpose processors are totaled and
managed together only with the total weights from all of the logical partitions using
the same processor type. The calculations shown in previous examples as well as
the examples to follow are done independently for general purpose, ICF, IFA, IFL,
or zIIP processors, on a machine that has them.
Processing Weights for Logical Partitions with Multiple Shared CP Types:
When a logical partition is defined to use one or more shared general purpose CPs
and one or more shared IFAs/zIIPs, each of the types of logical processors is
managed independently. The shared general purpose CPs compete with all other
shared general purpose CPs defined in other logical partitions in the configuration.
The IFAs compete with all other shared IFAs defined in other logical partitions. The
zIIPs compete with all other shared zIIPs defined in other logical partitions. General
purpose, IFA, and zIIP processors each have a separate processing weight
specified. Note that if WLM weight management is being used for such a logical
partition, only the weight of the shared general purpose processor portion of the
logical partition will be altered by WLM. The specified weight for an LP's IFA/zIIP
processors is unaltered by WLM.
Effects of Processing Weights: Several implications are derived from the rules
described above. First, every time a sharing LP is activated, the share of all other
active LPs, using the same processor types, changes. This happens because the
total of the processing weights has changed.
Because the processing share of LPs can vary, the actual utilization reported by
monitors such as RMF can be different from the weights. In systems at less than
100% utilization, some LPs could receive greater than their share if other LPs are
not using their share. The number of CPs defined also affects the maximum
300/1300 = 23.1%
100/1300 = 7.7%
900/1300 = 69.2%
23.1/1 CP = 23.1%
7.7/6 CPs = 1.3%
69.2/2 CPs = 34.6%