LRTF stands for Longest Remaining Time First. In the LRTF scheduling algorithm, the job that has the highest burst time is allocated CPU first. We keep monitoring the burst times periodically and assign the then highest burst time process to the CPU. It is a preemptive mode of the Longest Job First algorithm.
LRTF is a preemptive scheduling algorithm that adds an overhead than LJF, as the OS frequently monitors the CPU time of the processes in the READY queue and performs context switching when necessary. All the processes complete the execution around the same time irrespective of their burst size.
- Longest Remaining Time First is a CPU scheduling algorithm used to determine the process to be executed first among all the incoming processes in a systematic way.
- It follows the preemptive approach i.e. CPU is allocated only for a fixed slice of time.
- The criteria for process selection is highest burst size and this process runs till the fixed slice. The selection process takes place again.
- This is not an optimal scheduling algorithm as the average waiting time is high.
- LRTF algorithm is simple and easy to implement.
- Almost all the processes complete by the time the longest job reaches its completion.
- Starvation-free as all processes get fair share of CPU.
- The context switch consumes CPU’s valuable time which can be utilized for executing processes.
- Smaller processes need to wait for CPU to finish larger burst size processes.
- The average waiting time and average turn-around time are much high even with much less burst time of each process.
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