Lecture Operating systems: Lesson 14 - Dr. Syed Mansoor Sarwar

Lecture Operating systems: Lesson 14 - Dr. Syed Mansoor Sarwar. The main topics covered in this lesson include: short-term scheduler, CPU Scheduling, scheduling processes, dispatcher, fistogram of CPUburst times, reasons for invoking scheduler, optimization criteria, FCFS, SJF, and SRTF, . | Operating Systems Lecture 14 Agenda for Today Review of previous lecture Short-term scheduler Dispatcher Reasons for invoking scheduler Optimization criteria FCFS SJF and SRTF 28 April 2022 Copyright Virtual University of Pakistan Review of Lecture 13 Single and multi-threaded processes Thread models User- and kernel-level threads Pthreads library Sample multi-threaded code 28 April 2022 Copyright Virtual University of Pakistan Example 1 include include include Prototype for a function to be passed to our thread void MyThreadFunc void arg int main pthread_t aThread Create a thread and have it run the MyThreadFunction pthread_create amp aThread NULL MyThreadFunc NULL Parent waits for the aThread thread to exit pthread_join aThread NULL printf quot Exiting the main function. n quot return 0 28 April 2022 Copyright Virtual University of Pakistan Example 1 void MyThreadFunc void arg printf quot Hello world . The threaded version. n quot return NULL gcc o hello lpthread D_REENTRANT hello Hello world . The threaded version. Exiting the main function. 28 April 2022 Copyright Virtual University of Pakistan Example 2 include include define NUM_THREADS 5 void PrintHello void threadid printf quot n d Hello World n quot threadid pthread_exit NULL 28 April 2022 Copyright Virtual University of Pakistan Example 2 int main int argc char argv pthread_t threads NUM_THREADS int rc t for t 0 t lt NUM_THREADS t printf quot Creating thread d n quot t rc pthread_create amp threads t NULL PrintHello void t if rc printf quot ERROR return code is d n quot rc exit -1 pthread_exit NULL 28 April 2022 Copyright Virtual University of Pakistan CPU Scheduling Scheduling processes in the ready queue Short-term scheduler Different types of schedulers 28 April 2022 Copyright Virtual University of Pakistan Life of a Process 28 April 2022 Copyright Virtual University of Pakistan Histogram of CPU- burst Times 28 April 2022 Copyright Virtual University of Pakistan CPU Scheduler Short-term .