Computers as Components, 2nd Edition

330 CHAPTER 6 Processes and Operating Systems

<<signal>>

aSig

p: integer

someClass

sigbehavior( )

<<send>>

FIGURE 6.16

Use of a UML signal.

6.5 EVALUATING OPERATING SYSTEM PERFORMANCE

The scheduling policy does not tell us all that we would like to know about the

performance of a real system running processes. Our analysis of scheduling policies

makes some simplifying assumptions:

■ We have assumed that context switches require zero time. Although it is often

reasonable to neglect context switch time when it is much smaller than the

process execution time, context switching can add significant delay in some

cases.

■ We have assumed that we know the execution ...