Tc relate these measurement values to system workload for a specific
configuratien, an installation must define its workload. The definition
cf workload varies with the environment:
Interactive time-sharing
system
Batch system
Arrival rate of transactions and the CPU time
and working set size required for each
transaction.
Job throughput and resource requirements (CPU time, region or partition size, and number of EXCPs issued) for each job.
By using these workload definitions, an installation can measure its
workload under as follows: users under OFerating system under VM/370 Number of active users User I/O requests executed When both an operating system and users run under the
system, workload measurement depends upon which type of
dominates the VM/370 system.
same environment
To measure workload performance in a specific configuration, an
installation can use the Field Developed program VM/370 Performance/Mcnitor Analysis program (5798-CPX). This program plots a
number of important system variables (such as CPU usage, various
centention measurements, and paging rates) against workload measurement
fer both the and operating system workloads under VM/370. For a
sFecific configuration, it allows an installation to relate processor
usage, storage usage, and resource contention to the total system
workload in beth interactive and batch production environments.
By using this analysis program, an installation can eventually
determine its optimum processor model, storage size, and l/C
configuraticn fer a specific workload. Thus, an installation may
determine that it needs to do such things as: redistribute data sets to
reduce arm centention, add control units and channels to reduce l/C
centention, and add paging devices to reduce interference between system
and user I/O Frocessing.
These specialized software techniques influence the performance
of an operating system in a virtual machine: • Whether VH/VS handshaking is used. • The tYFe and number of VM/370 performance options in use by one or more virtual machines. • Whether the VM/370 System Extensions Program Product
used. (5748-XE1) is VM/VS handshaking (described earlier in this section
under the teFic "VM/VS Handshaking") permits instructions issued by an
oFerating system in a virtual machine to be processed directly by the
Frocessor. It also permits VM/370 to simulate privileged instructions. Section 1. General Considerations 35

QE!!Qn§: After measuring the performance of both VM/370 and the virtual machines it supports, the system analyst and the
general user can each use certain VM/370 performance options. These oftions allow them to create a special performance environment for one
cr more virtual machines. The options allow: • The system analyst to redistribute system resources either to balance
inequities or to favor one virtual machine over another. • The general user to improve the performance for his virtual machine.
The VM/370 system operator, on behalf of the system analyst, can give
certain oftions to a specific virtual machine to improve its performance
over other virtual machines. A general user has certain performance
options that give limited control over his virtual machine. The options
available to the system operator and the general user are: Locked pages option
Reserved page frames
Priority
Favored execution option Virtual machine assist VM/370 extended control-program support Virtual=real option
1
In the following list, the first option and either of the next two oftions can be applied to only one virtual machine at a time. • Favored execution with guaranteed percentage • Reserved page frames • Virtual=real option
1
The following options can be applied to as many virtual machines
as desired: • Basic favored execution (without guaranteed percentage) • priority • Virtual machine assist • VM/370 extended control-program support (HepS: • Locked pages
For basic information about these options, refer to the For details about specifying the options for the
system operator, refer to Guide. For details about
specifying the options for the general user, refer to f££ The System Extensions program Product (S748-XE1) provides several performance-related additions to the system control program. For certain environments, these additions: • Improve throughput • Provide better terminal response
1This option cannot be specified in a command. To obtain it. a qenpral user requests the VM/370 system programmer to specify it on control statement (VIRT=REAL option) for the user's virtual machine
directory entry_ 36 :BM VM/370 operating Systems in a Virtual Machine