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Summary: 7
Scheduling: Introduction
By now you should understand the basic machinery of running
processes, including how to context-switch between processes
and the details therein. Thus, the low-level mechanisms should
be clear.
However, we have yet to understand the high-level policies
that the OS scheduler employs. In this note, we will do just
that, presenting a series of scheduling policies (sometimes called
disciplines) that people have developed over the years.
We will now develop some scheduling policies that have been
put forth through the years. The origins of scheduling, in fact,
predate computer systems, as early approaches were taken from
the field of operations management and applied to computer
systems. This should be no surprise: assembly lines and many
other human constructions also require scheduling.
7.1 Workload Assumptions
Before getting into the range of possible policies, let us first
make a number of simplifying assumptions about the processes
running in the system, sometimes collectively called the work-
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