High-Performance Embedded Computing

6.4 Embedded Multiprocessors 371

other scheduling methods or mix scheduling policies, we must ensure that the

processes that need quality-of-service obtain the level of service they need.

QoS model Quality-of-service can be modeled using three basic concepts. First, a contract

specifies the resources that will be provided. The client may propose a set of

terms, such as the amount of bandwidth and rate of missed packets, but the

server may counterpropose a different set of terms based on its available

resources. A protocol manages the establishment of the contract and its imple-

mentation. Third, a scheduler implements the terms of the contract, setting the

sizes of buffers, managing bandwidth, and so on.

QoS and

resources

Assuming that we run a QoS-friendly ...