📌  相关文章
📜  LJF和LRJF CPU调度算法的区别

📅  最后修改于: 2021-09-12 11:19:47             🧑  作者: Mango

1. 最长工作优先(LJF):
它是 CPU 调度算法,其中具有最大突发行的进程首先执行。一旦进程进入就绪队列,则该进程只有在执行完成后才退出,因此它是一个非抢占式进程。如果进程的突发次数相同,则选择总体时间最短的作业。这种CPU调度算法导致系统吞吐量低。

Process AT BT
1 0 3
2 1 2
3 2 4
4 3 5
5 4 6

2. 最长剩余工作优先(LRJF):
它是最长作业优先 CPU 调度算法的抢占式版本。每秒选择一次处理突发时间,然后选择最长的作业。如果进程的突发时间相同,则选择总体到达时间较短的作业。

它遭受饥饿,因为同时检查进程的剩余突发时间。它也被称为“最长剩余时间优先”算法。

Process AT BT
1 0 3
2 1 2
3 2 4
4 3 5
5 4 6

LJF和LRJF CPU调度算法的区别:

LJF LRJF
Non preemptive Preemptive
It suffers from starvation It also suffers from starvation
Waiting Time is high Waiting Time is not so high, and processes get chances for execution after some interval.
Switching context is less, since a process that once enters running state is executed completely. Switching context is more, since the process are continually checked for execution.
The processes are executed based on their CPU time and arrival time alone, without increasing CPU overload. The processes are repeatedly checking for an idle CPU, thereby increasing the overload.
No process can complete its execution until longest job persists. The processes can complete execution before the longest process.