Performance Options VM/370 offers the following performance options to enhance the operating
efficiency of one oraore virtual machines. This enhancement is
nor. ally at the expense of the performance of other virtualmachines. In certain instances, enhancements to a specific virtual machine (or
aultiple virtualmachines) are detrimental to the operating efficiency
of other virtual The performance options are: • Virtual machine assist • VM/370 Extended Control-Program Support • Reserved page frames • Favored execution • Virtual=real • Locked pages • Priority • Affinity in an attached processor environment You can dynaMically assign or withdraw any of these options except
for the virtual=real option (it can only bedynamically withdrawn) fro.
virtual machine users duringsystem operations. You can assign to one
virtual machine a"mix" of performance options, or the options may be
assigned to separate virtual machines. Efficient use of these options
depends upon the characteristics of theprogram applications; the nUMber, size, and complexity of the virtual machines being run; and the
size,I/O configuration, and CPU model of the real computer being used.
In addition to using these performance options,you can also use the SET PRIORITY command to change a virtual machine's execution priority
and, thereby, change its performance.For example, you could assign the following mix of One virtual machine: Reserved Pages=10 Favored Execution=80% Virtual Machine Assist
Another virtualmachine: Virtual=Real priority=1
A third virtual machine:
LockedPages=2 The favored execution (with percentage value specified), VIRT=REAL, and the reserved page option are unique in that each option cannot be
applied tomultiple virtual machines at the same time. However, no.such
restrictions apply to the locked pages, virtual machine assist,VM/370 Extended Control-Program Support, priority, or favored execution
(without the percentage value) options; they can beapplied' to multiple virtual machines. RESERVED PAGE FRAMES OPTION The CP paging routine uses chained lists of available and pageable pages
to control real storage use.CP assigns pages for users from the
available list, which it replenishesfrom the pageable list.
Section 2. InitiatingVM/370 Operation 27
efficiency of one or
nor. ally at the expense of the performance of other virtual
aultiple virtual
of other virtual
for the virtual=real option (it can only be
virtual machine users during
virtual machine a
assigned to separate virtual machines. Efficient use of these options
depends upon the characteristics of the
size,
In addition to using these performance options,
and, thereby, change its performance.
Another virtual
A third virtual machine:
Locked
applied to
restrictions apply to the locked pages, virtual machine assist,
(without the percentage value) options; they can be
to control real storage use.
available list, which it replenishes
Section 2. Initiating