Calculating The Precise Processor Utilization; Mode Of Operation Of The Task Administrator - Siemens SIMADYN D Manual

Systemsoftware

2.1.9.2 Calculating the precise processor utilization

Function block PSL

2.1.9.3 Mode of operation of the task administrator

2-32
After the charts of a CPU have been compiled using the CFC editor via
the menu item Chart > Compile the path of a MAP list is specified in an
info window or in an error window. The processor utilization, entered in
the MAP list, is an approximate value for the reasons mentioned above,
which is generally accurate to approximately +/- 10 %.
The precise CPU utilization can only be determined when the PSL
"Permanent System Load" block is configured. The PSL block is
configured in any cyclic task in the CPU to be investigated.
It has 5 outputs (Y1..5) which display the actual utilization of the
individual tasks in the form of a load factor. The displayed factor should
not exceed 1.0 (100%). Values exceeding 1.0 indicate that a CPU is
overloaded.
Further, the PSL block has 5 inputs (T1..5) which, for each task, can be
used to simulate an additional load in milliseconds (ms). It is then
possible to read how such a load effects the utilization of the individual
tasks at the outputs. The utilization is determined by measuring the task
run times and then dividing this by the actual sampling time. Higher
priority tasks occur within the run time of a task which extend the run time
and noticeably increase the utilization. Thus, by just adding these values,
it isn't possible to obtain an overall utilization level.
Sampling time of
task T1 = 100 %
50 %
T1
90 % utilization
25 % 25 %
T2
Sampling time of
task T2 = 100 %
Idle time of
the task(s)
Fig. 2-11 Calculating the run time
The mode of operation of the task administrator is illustrated in this
Chapter in Fig. 2-12
If a task can be completed within a basic sampling time due to a low
computation time, then this is illustrated in the 1st cycle.
50 % 50 %
25 %
15 %
Actual task run
time(s)
Sequence of a configured task.
System- and communication configuring D7-SYS - SIMADYN D
50 %
25 % 15 %
Edition 03.2001