Summary :-Distributed Process Scheduling Prepared By:- Monika Patel.

Outline:- Summary of Chapter 5 A System performance model Static process scheduling Dynamic load sharing and balancing Distributed process implementation Real time scheduling

A system performance model It gives relationship among algorithm, scheduling and architecture. Basically three types of model are there:- Precedence process model:-In this processes are represented by a Directed Acyclic graph (DAG). This is best applied to the concurrent processes generated by concurrent languages constructs such as fork/join.

Communication process model :- In this model processes are created to co-exist and communicate asynchronously. It minimizes the interprocessor communication and computation costs of processes on processors. Disjoint process model:-In this processes run independently and completed in finite time. Processes are mapped to the processors to maximize the utilization of processes and minimize the turnaround time of the processes.

Static Process Scheduling The mapping of processes to processor is determined in advance, before the execution process. Once process started it stays at the processor until completion of the process. It’s never prompted to move to another processor.

Dynamic load sharing and Balancing Load balancing can be defined as a technique to distribute work between many computers,processes or any other resources to get optimal resource utilization. A process used to route signaling traffic over two or more signaling routes for purposes of traffic equalization or security.

Sender Initiated Algorithm It is activated by a sender process that wishes to off-load some of its computation. It also give facility of migration of processes from a heavily loaded sender to a lightly loaded receiver. Transfer of process form a sender to reciever requires three basic decision. Transfer policy:-when does the node become the sender? Selection Policy:-How does the sender choose a process for transfer? Location Policy:-which node should be the target reciever?

Receiver initiated Algorithm:- This are the pull models in which receiver can pull a process from others to its site for execution. They are more stable than the sender initiated algorithm. At high system load,process migration are few and a sender can be found easily.

Distributed process implementation Remote Service:-The message is interpreted as a request for a known service at the remote site Three different software levels:- As remote procedure calls at the language level. As remote commands at the operating system level. As interpretive messages at the application level.

Remote execution:-The message contain a program to be executed at the remote site. Some Implementation issues:- load sharing algorithms. Location independence. System heterogeneity. Protection and security.

Process Migration:-The message represents a process being migrated to the remote site for continuing execution. Link Direction and message forwarding -Real time example is address changing before moving. State and context transfer:-It transfers the computation state information and some initial codes.

Real Time Scheduling:- The systems which insures that certain actions are taken within specified time constraints are called real time systems. Examples:- Avionics Computers. Automobile Control Computers. Factory automation systems. Stock trading Systems.

Rate Monotonic:- It’s easy to implement. Sorts the tasks by the lengths of their periods. It also makes very good priority assignments. Rate monotonic is an optimal priority assignment algorithm.

Deadline Monotonic:-In real time system some tasks need to complete execution a short time after being requested. Earliest Deadline First:-this is applicable to scheduling aperiodic real time tasks because it only uses the deadlines of the task instantiations. Real time Synchronization:-A set of tasks that cooperate to achieve a goal will need to share information and resources or other words synchronize with other tasks.

Refrences:- [1] Distributed operating systems & Algorithms,By Randy chow,Theodore johnson.

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