The interaction between the various components of an operating system is critical to achieving good performance. Discuss the interaction between the memory manager and the job initiator (i.e., admission scheduler) in a virtual-memory multiprogramming system. In particular, suppose the memory manager uses a working set memory-management approach.

Question

What will be an ideal response?

Answer 1

Clearly, the job initiator does not want to initiate jobs that will cause system resources
in general, and memory in particular, to become overcommitted. So the job initiator interacts
with the memory manager to see if sufficient space is available to hold the incoming job.This
is a nontrivial decision, however, because before a process begins execution, its working set
size must be estimated. Needless to say, this is difficult to do with any degree of accuracy,
especially because the size of the working set can vary considerably as the process transitions
between phases. Accordingly, many systems use simple heuristics, such as initiate the job if x
pages are available, or initiate the job if space to hold y percent of its virtual space is available,
and so on.