Day 01 Part 17(B)- Concept of schedulers short term, long term and medium term schedulers<\/p>\n
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In operating systems, schedulers<\/strong> are responsible for managing the execution of processes by determining which process runs at a given time.<\/span> There are three primary types of schedulers: Long-Term<\/strong>, Medium-Term<\/strong>, and Short-Term<\/strong>.<\/span> Each plays a distinct role in process management and system performance.<\/span><\/p>\n Role:<\/strong> Determines which processes are admitted into the system for processing.<\/span><\/p>\n Functions:<\/strong><\/p>\n Controls Multiprogramming:<\/strong> Regulates the number of processes in memory to maintain an optimal level of multiprogramming.<\/span><\/p>\n<\/li>\n Process Selection:<\/strong> Chooses processes from the job pool and loads them into the ready queue.<\/span><\/p>\n<\/li>\n Process Mix:<\/strong> Ensures a balanced mix of I\/O-bound and CPU-bound processes to optimize resource utilization.<\/span><\/p>\n<\/li>\n<\/ul>\n Characteristics:<\/strong><\/p>\n Frequency:<\/strong> Invoked less frequently compared to other schedulers.<\/span><\/p>\n<\/li>\n Speed:<\/strong> Slower decision-making process.<\/span><\/p>\n<\/li>\n Presence:<\/strong> Not present in all systems; for instance, time-sharing systems like UNIX often lack a long-term scheduler.<\/span><\/p>\n<\/li>\n<\/ul>\n Role:<\/strong> Manages the swapping of processes in and out of main memory to optimize CPU and memory utilization.<\/span><\/p>\n Functions:<\/strong><\/p>\n Swapping:<\/strong> Temporarily removes (swaps out) processes from main memory to reduce the degree of multiprogramming and later swaps them back in when appropriate.<\/span><\/p>\n<\/li>\n Resource Management:<\/strong> Balances memory usage among processes, ensuring efficient utilization.<\/span><\/p>\n<\/li>\n Process Prioritization:<\/strong> May adjust process priorities based on their current state or resource requirements.<\/span><\/p>\n<\/li>\n<\/ul>\n Characteristics:<\/strong><\/p>\n Frequency:<\/strong> Operates at a medium frequency, depending on system load and memory availability.<\/span><\/p>\n<\/li>\n Presence:<\/strong> Common in systems that support swapping; not all operating systems implement a medium-term scheduler.<\/span><\/p>\n<\/li>\n<\/ul>\n Role:<\/strong> Selects which process in the ready queue should be executed next by the CPU.<\/span><\/p>\n Functions:<\/strong><\/p>\n Process Dispatching:<\/strong> Allocates CPU to one of the ready processes.<\/span><\/p>\n<\/li>\n Context Switching:<\/strong> Handles the switching of the CPU from one process to another.<\/span><\/p>\n<\/li>\n Scheduling Algorithms:<\/strong> Implements algorithms like First-Come-First-Serve (FCFS), Shortest Job Next (SJN), Round Robin (RR), etc., to determine process execution order.<\/span><\/p>\n<\/li>\n<\/ul>\n Characteristics:<\/strong><\/p>\n Frequency:<\/strong> Invoked very frequently (milliseconds), making rapid decisions.<\/span><\/p>\n<\/li>\n Speed:<\/strong> Fastest among all schedulers due to the need for quick decision-making.<\/span><\/p>\n<\/li>\n Presence:<\/strong> Essential component in all operating systems.<\/span><\/p>\n<\/li>\n<\/ul>\n
\n\ud83d\udd52 Long-Term Scheduler (Job Scheduler)<\/h3>\n
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\n\ud83d\udd51 Medium-Term Scheduler (Swapper)<\/h3>\n
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\n\ud83d\udd50 Short-Term Scheduler (CPU Scheduler)<\/h3>\n
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\n\ud83d\udcca Comparative Overview<\/h3>\n