admin In a multiprocessing environment, several processes compete for limited resources. A running process goes to waiting state when a resource is not available. The process could not change its state because some other process holds the resources. This is called a deadlock. Normal Conditions The operating system does not provide with deadlock prevention mechanism, the … Read more
The shortest job first (SJF) algorithm is preemptive or non-preemptive. You have learned about the non-preemptive SJF in the previous article. In this article, you will learn about preemptive SJF, also called the shortest remaining time first scheduling algorithm. Preemptive SJF A new process arrives at the ready queue while an old process is executing … Read more
A multilevel queue is suitable when the processes are classified in groups. The multilevel queue scheduling algorithm partition the queue into several separate queues. Each of the processes are permanently assigned to one queue based on some property such as memory requirement, process priority, or process type. Then each queue has its own scheduling algorithm. … Read more
The fork-join is a basic method of expressing concurrency within a computation. This is implemented in the UNIX operating system as system calls. Fork The fork() call creates a new child process which runs concurrently with the parent. The child process is an exact copy of the parent except that it has a new process … Read more
There are certain conditions for concurrency. Here we have listed them for you in this article. Conditions for Concurrency , the read set for , is the set of all variables whose values are referenced in statement during its execution. , the write set for , is the set of all variables whose values are … Read more
A precedence graph is a directed acyclic graph whose nodes corresponds to individual statements. An edge from to , implies that statement can only be executed after statement has completed execution. In the above diagram following precedence relation is shown: S2 and S3 can be executed only after S1 has finished execution. S4 can be … Read more
A scheduling algorithms like round-robin treat all processes as same. But if we consider other information about a process, some process is more important than the other. This is the motivation behind priority scheduling. Each process carries a priority and process with the highest priority will be allocated CPU time. Since there is a chance … Read more
The shortest job first algorithm associates the length of the next CPU burst with each process. The CPU time is assigned to a process with the smallest next CPU burst time. Gantt Chart for SJF If there are two processes with the same next CPU burst time, then FCFS algorithm is applied to them. Consider … Read more
The round-robin scheduling algorithm is suitable for time-sharing computers which are similar to FCFS. However, preemption is added to this algorithm to switch between processes. A time slice is defined called time quantum which is typically 10 to 100 milliseconds. The processes are allocated CPU time up to 1-time quantum. Then the process is preempted … Read more
The first come first served (FCFS) is the simplest CPU-scheduling algorithm. The process which requests CPU first will be allocated CPU first and so on. The process enters the ready queue and its PCB is linked to the tail of the queue. When the CPU is free, it is assigned a new process from the … Read more
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