Here is a comparison between the Longest Job First (LJF) and Longest Remaining Job First (LRJF) scheduling algorithms in CPU Scheduling in operating systems :
| Feature | Longest Job First (LJF) | Longest Remaining Job First (LRJF) |
|---|---|---|
| Responsiveness | Lower waiting time for processes, leading to high responsiveness | Lower waiting time for processes, leading to high responsiveness |
| Memory requirements | Requires additional memory for scheduling information | Requires additional memory for scheduling information |
| Task completion | Results in longer completion time for tasks | Results in shorter completion time for tasks |
| Performance prediction | Difficult to predict performance | Easy to predict performance |
| Overhead | Lower overhead compared to priority scheduling | Higher overhead compared to priority scheduling |
| Load balancing | Results in unbalanced distribution of load | Results in balanced distribution of load |
| Real-time applications | Not suitable for real-time applications | Suitable for real-time applications |
| Batch processing | Suitable for batch processing | Suitable for batch processing |
| Multitasking | Not suitable for multitasking | Suitable for multitasking |
| Scheduling decisions | Based on burst time | Based on remaining burst time |
| Process state | Process state information is not required | Process state information is required |
| Predictability | Poor predictability | Good predictability |
| Starvation | Can cause starvation of short processes | Prevents starvation of long processes |
| CPU utilization | Lower average CPU utilization | Higher average CPU utilization |
| Process preemption | Does not allow process preemption | Allows process preemption |
In conclusion, LJF and LRJF are scheduling algorithms used in CPU Scheduling in operating systems. LJF executes the process with the longest burst time first, while LRJF executes the process with the longest remaining burst time first. While LJF is suitable for batch processing, it is not suitable for real-time applications and multitasking. On the other hand, LRJF is suitable for real-time applications and multitasking but requires additional process state information. The choice of scheduling algorithm depends on the specific requirements and constraints of the system and the workload being scheduled.
