margin-right: 0pt;
text-align: left; text-indent: 0pt; line-height: 40pt;">Resident Set Size

Fixed-allocation policy

Allocates a fixed number of frames that  remains
constant over time

The number is determined at load time and depends
on the type of the application

Variable-allocation policy

The number of frames allocated to a process may vary
over time

May increase if page fault rate is high
May decrease if page fault rate is very low

Requires more OS overhead to assess behavior of active
processes

3

Replacement Scope

Replacement scope determines the set of frames to
be considered for replacement when a page fault occurs
Local replacement policy

Chooses only among the frames that are allocated to
the process that issued the page fault

Global replacement policy

Any unlocked frame is a candidate for replacement

Let us consider the possible combinations of replacement
scope and resident set size policy

4

Fixed allocation and Local scope

Each process is allocated a fixed number of pages

Determined at load time and depends on application
type

When a page fault occurs, page frames considered for
replacement are local to the page-fault process

The number of frames allocated is thus constant
Previous replacement algorithms can be used

Problem: difficult to determine ahead of time a good
number for the allocated frames

If too low: page fault rate will be high
If too large: multiprogramming level will be low

5

Fixed allocation and Global scope

Impossible to achieve