Lec03 - Processes and Threads Processes and their...

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Computer Science Lecture 3, page CS677: Distributed OS Processes and Threads Processes and their scheduling Multiprocessor scheduling Threads Distributed Scheduling/migration 1 Computer Science Lecture 3, page CS677: Distributed OS Processes: Review Multiprogramming versus multiprocessing Kernel data structure: process control block (PCB) Each process has an address space Contains code, global and local variables. . Process state transitions Uniprocessor scheduling algorithms Round-robin, shortest job first, FIFO, lottery scheduling, EDF Performance metrics: throughput, CPU utilization, turnaround time, response time, fairness 2
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Computer Science Lecture 3, page CS677: Distributed OS Process Behavior Processes: alternate between CPU and I/O CPU bursts Most bursts are short, a few are very long (high variance) Modeled using hyperexponential behavior If X is an exponential r.v. Pr [ X <= x] = 1 – e - μ x E[X] = 1/ μ If X is a hyperexponential r.v. Pr [X <= x] = 1 – p e - μ1 x -(1-p) e - μ2 x E[X] = p/ μ1 + (1 ! p)/ μ2 3 Computer Science Lecture 3, page CS677: Distributed OS Process Scheduling Priority queues: multiples queues, each with a different priority Use strict priority scheduling Example: page swapper, kernel tasks, real-time tasks, user tasks Multi-level feedback queue Multiple queues with priority Processes dynamically move from one queue to another Depending on priority/CPU characteristics Gives higher priority to I/O bound or interactive tasks Lower priority to CPU bound tasks Round robin at each level 4
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Computer Science Lecture 3, page
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Lec03 - Processes and Threads Processes and their...

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