Possible System Performance When A Virtual Storage; Operating System Is Used With An Existing Model; Configuration - IBM System/370 145 Manual

Panel 1
Sample existing CPU and I/O
utilization and overlap for
Model 145.
EXISTING SYSTEM THROUGHPUT
MAINTAINED
Panel 2
a
Some of the additional CPU and I/O
time required is overlapped with pre-
viously unoverlapped I/O and CPU time
(points A). Additional CPU and I/O
time that cannot be overlapped
(points B) is offset by a reduction
in the amount of CPU and I/O time
required to process the same job
stream. Results are achieved in the
same elapsed time.
Panel 3
cpt
(a)
-I
I ..
(b)
I/O
\..
,,~----------------~I
Elapsed Time
i
®
CPU
-I-
I/O
Reduced CPU Time
"I
~
1
1 __
I~_~
________
R_e_d_uc_e_d_I_/O ________ ~_~1
_
® ®
Additional CPU and I/O time required
(dotted lines) is overlapped and off-
set by operating the system ata
higher level of multiprogramming to
achieve greater overlap. Results are
aChieved
in
the same elapsed time.
CPU
--I . . . .
- - - ( a _ )
-----.l-~I--I
EXISTING SYSTEM THROUGHPUT IMPROVED
Panel 4
unoverlapped CPU and I/O time required
is exceeded by reductions in previ-
ously used CPU and I/O time. Better
overlap of previously used CPU and I/O
time is also achieved. Same results
are aChieved in less elapsed time.
Panel 5
A higher level of multiprogramming
is used to perform more work and
achieve better overlap of CPU and I/O
time. More results are achieved in
the same elapsed time.
I/O
~-It04
_____
{_b) _ _ _
~_I
_
\.~---..
.......... _ _ --...,I
Better Overlap
CPU
_I_
Reduce~
CPU Time
"1--1
I/O
1 __
1_
Reduced I/O Time
~
·1--
\. Better Overlap
J
,,---------------~
Elapsed Time Reduced
I
Increased CPU Time
I
1
CPU -- ..... - - - - - - - . .. --.
I/O
1 __
I' " .. __
--------I-nc-r-ea-s-ed.-..;..I/-O-T-im--e------........-t ..
I--
~----------~_---------I
Better Overlap
Figure 15.15.1. possible system performance when a virtual storage
operating system is ulEied with an existing Model 145
configuration
Existing throughput is maintained ijE both of the following occur:
1. A portion of the additional CPU and I/O time required to support
a virtual storage environment
i~J
overlapped with CPU and I/O time
that previously was not overlapped, as shown by points A in panel 2.
A Guide to the IBM System/370 Model 14S 81