Summary :-Distributed Process Scheduling

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Summary -Distributed Process Scheduling

• Prepared By-
• Monika Patel.

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Outline-

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

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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.

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• 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.

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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.
• Its never prompted to move to another processor .

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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.

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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?

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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.

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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.

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• 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.

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• 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.

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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.

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Rate Monotonic-

• Its 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.

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• 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.

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Refrences-

• 1 Distributed operating systems Algorithms,By
  Randy chow,Theodore johnson.

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• Thank You.