Performance Guidelines
Performance Guidelines The performance characteristics of an operating system when it is run in
a virtual machine environment are difficult to predict. This
unpredictability is a result of many factors: The System/370 model used The system environment used (uniprocessor or attached processor) The total number of virtual machines executing The type of work being done by each virtual machine The speed, capacity, and number of the paging devices The amount of real storage available The degree of channel and control unit contention, as well as arm
contention, affecting the paging device The type and number of VK/370 performance options in use by one or
more virtual machines The availability of VM/370 hardware assist The favored priority and V=R options in effect
Also, the virtual machine's channel mode, block multiplexer or selector,
has an effect on the virtual machine's performance. !Qig: The performance of an KSS being accessed by
and shared with other systems depends on the total
contention.
Performance Measurement and Analysis
the operating system KSS utilization and
The VK/370 control program has two commands that measure system
performance and, thus, help you identify problem areas. The MONITOR command collects system measurement data offline for the system operator
or system analyst, while the INDICATE command displays system
measurement data online for the system operator, system analyst or
gen eral user.
The MONITOR command controls the collection of performance data and
writing it to system spool files or tapes. Both summary and trace data
can be collected. The classes of data collected may be specified using
either the operands of the MONITOR command or those of the SYSMON macro
instruction. The classes selected depend on the nature of the analysis
to be performed. The IBM Field Developed Program (FOP) VM/370: Performance/"onitor Analysis Program can be used to reduce the data
collected. The guidelines for using this program provide the user with
information that will aid him in determining the overall load
environment and performance profile of his system. The VM/370 Performance/Monitor Analysis Program should enable him to analyze the
utilization of and contention for the major system resources such as the CPU, storage, and I/O paging subsystems. Part 1. Planning for System Generation 7
Performance Guidelines
The INDICATE command displays, at the terminal, some key information
about the system that shows the current performance indicators.
Invoking the INDICATE command displays the system conditions existing at
the time the command is issued including attached processor utilization
measurement when operating in an attached processor environment. If,
after using the INDICATE command, the system analyst wants more
extensive data collection and reduction, he can use the MONITOR command.
The user can specify automatic data collection with the SYSMON macro
in DMKSYS. Coding Considerations are contained in the section "Preparing the CP System Control File (DKKSYS)." See the !I1LJIQ for the directions on using the MONITOR command to
collect performance data on a dedicated tape drive or spool file, the
format and contents of the various classes of data collection available
with MONITOR, and details of the INDICATE command options.
Using the Performance Options
The performance of a specific virtual machine can be improved by
assigning it one or more performance options. These include: favored
execution, priority, reserved page frames, locked pages, and
virtual=real.
The performance of a VM/370 system running virtual storage operating
systems can be improved if you use virtual machine assist or Extended
Control-Program Support. The manner in which these are supported by the
various VK/370 processors is detailed below:
r , Virtual Machine Assist VM/370:ECPS 1---------------------------------------------------------------------------- 1 Standard I Feature
135-3
13A
145-3 14A 3031 3031 AP 4341 1 1 Special Feature
135
145
158
158-3 158AP 158MP 4331 1 RPQ 168
168-3 168AP 168MP 3032 3033UP 3033AP 3033MP 1 Not ,Standard IAvailablel Feature
155 155I1 165
165-3
135-3
138
145-3
148
3031
2 3031 AP2 4341 Special I Not
Feature IAvailable 4331
12
135
145
155
155II
158
158-3 158AP 158MP 165
165- 3 168AP 168MP 3032 3033 3033AP 3033MP 1 ITo function with the availability of the hardware feature. I I I L 2See the for specific VM/370: EPCS functions available on this processor.
8 IBM VM/370 Planning and System Generation Guide
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