1.最长的工作优先(LJF)：
最长作业优先(LJF)基于过程的突发时间。根据进程的突发时间将其放入就绪队列。在该算法中，首先处理突发时间最大的过程。仅比较那些在该时间之前存在或已经到达的进程的突发时间。它在本质上也是非抢先的。它的抢占版本称为最长剩余时间优先(LRTF)算法。
该算法的主要缺点是对于给定的一组过程，它会提供非常高的平均等待时间和平均周转时间，从而降低了系统的效率。这也可能导致车队效应。
笔记 –
如果两个进程的突发时间相同，则使用FCFS断开连接，即首先处理最先到达的进程。
2，罗宾(RR)：
轮询(RR)调度算法是专门为时间共享系统设计的。进程被放入就绪队列，在这种情况下，该队列是循环队列。在这种情况下，定义了一个小的时间单位，称为时间量。该算法从队列中选择第一个进程，并在时间量所定义的时间内执行它。如果该进程的突发时间小于该时间量，则CPU执行下一个进程，但如果其突发时间大于该时间量，则该过程被中断，并针对相同的时间量执行下一个进程。如果某个进程被中断，则会发生上下文切换，并将该进程放回队列的尾部。它本质上是先发制人的。
该算法主要取决于时间量。很大的时间量会使RR与FCFS相同，而很小的时间量将导致开销，因为上下文切换将在非常小的间隔后一次又一次地发生。
该算法的主要优点是，所有进程都一个接一个地执行，这不会导致进程出现饥饿或等待进程等待很长时间才能执行。最长作业优先(LJF)和轮询(RR)调度算法之间的区别如下：
| Longest Job First (LJF) | Round-Robin (RR) |
|---|---|
| Longest Job First (LJF) executes the processes based upon their burst time i.e. in descending order of their burst times. | Round-Robin (RR) executes the processes based upon the time quantum defined i.e. each process is executed for a fixed amount of time. |
| LJF is also non-preemptive but its preemptive version is also there called Longest Remaining Time First (LRTF) algorithm. | Round-Robin (RR) is preemptive in nature. |
| The average waiting time and average turn-around time for given set of processes is very large. | The average waiting time for given set of processes is quite small and depends on the time quantum. |
| The LJF algorithm is difficult to implement. | It is quite easy to implement RR. |
| A short process may never get executed and the system may keep executing the longer processes and a user may feel that his work is being neglected in case of multi user systems. | Each process is executed and every user feels that his work is being done as the CPU gives equal amount of time to each process. |
| In case of LJF, very large waiting time leads to slow processing and reduces the effectiveness of the system. | In case of RR, if the time quantum is very small then context switch takes place again and again after very short intervals of time which leads to overhead. |