MPE/iX Commands Reference Manual (32650-90877)

Chapter 14 607
Command List XII
Commands STREAM thru XEQ
provided for compatibility, avoid setting the base priority between 150 and
152, since user processes running at priorities greater than 152 can
adversely affect system performance.
limit An integer specifying the lowest priority at which a process in the CS, DS,
or ES scheduling subqueues can execute. Priority is inversely related to
the integer: a higher-priority process has a lower number. The
limit ,
which can range from 150 to 255, must be greater than or equal to the
base .
min The minimum quantum is a lower bound for the dynamically calculated
quantum (average transaction time) value. The quantum value
determines the rate of priority decay for processes within the scheduling
subqueue. Values range between 1 and 32767 milliseconds.
max The maximum quantum is an upper bound for the dynamically calculated
quantum (average transaction time) value. The quantum value
determines the rate of priority decay for processes within the scheduling
subqueue. Values range between 1 and 32767 milliseconds. The value of
max must be greater than or equal to the value of min .
DECAY Sets the subqueue to the default decay behavior associated with circular
scheduling subqueues. If set, a process decays normally to the
limit
priority and returns to the base priority when the Dispatcher transaction
is complete. DECAY is the default boost property.
OSCILLATE Sets the subqueue to oscillate behavior. If set, a process returns to the
base priority once its priority has decayed to the limit of the subqueue,
even if it has not completed a Dispatcher transaction.
tslice The number of milliseconds a process in a given subqueue can hold the
CPU. A process that has held the CPU continuously for this number of
milliseconds is interrupted. This value must be set to a multiple of 100
milliseconds and has a minimum value of 100 milliseconds.
OPERATION
The system manager uses the TUNE command to change the characteristics of the circular
scheduling subqueues to more efficiently manage the current processing load.
A process in the CS, DS, or ES scheduling subqueues typically begin execution at the
base
priority. When the process stops (for disk I/O, terminal I/O, preemption, etc.), the amount
of CPU it has consumed is used to determine its new priority. If the process has completed
a Dispatcher transaction, typically by issuing a terminal read, its priority is reset to the
base , and the quantum value for that workgroup is recalculated. If the process has
exceeded the quantum (filter) value since its priority was last reduced, the priority is
decreased without exceeding the
limit priority. If the boost property for the workgroup is
oscillate, process priorities are reset to the
base value once they decay to the limit .
The parameters
min and max refer to the absolute bounds of the quantum, or a filter
representing the average transaction time of processes in that subqueue. The quantum is
recomputed after every user Dispatcher transaction is complete, and then compared
against the CPU time of a process to determine whether the priority of the process should
be decreased.