linux进程的调度机制为以下哪一个 A 时间片轮询机制 B 先来先服务算法 C 分级调度算法 D 以上都不是
时间: 2024-05-27 07:09:57 浏览: 16
A 时间片轮询机制。Linux进程的调度采用时间片轮询机制,即将CPU的运行时间划分为若干个时间片,每个进程占用一个时间片,时间片用完后,该进程被挂起,等待下一次调度。如果一个进程在时间片用完之前就已经执行完毕,那么它会被立即结束,让出CPU资源。如果系统中有多个进程处于就绪状态,那么调度程序会按照一定的顺序轮流为它们分配时间片,保证每个进程都有机会获得CPU资源。
相关问题
一个c语言代码实现先来先服务调度算法、短作业优先算法、时间片轮转和优先级调度算法
先来先服务调度算法(FCFS):
```c
#include <stdio.h>
#define MAX 10
struct Process {
int pid;
int arrival_time;
int burst_time;
int waiting_time;
int turnaround_time;
};
int main() {
struct Process p[MAX];
int n, i;
float avg_waiting_time = 0, avg_turnaround_time = 0;
printf("Enter the number of processes: ");
scanf("%d", &n);
for(i=0; i<n; i++) {
printf("Enter arrival time and burst time for Process %d: ", i+1);
scanf("%d %d", &p[i].arrival_time, &p[i].burst_time);
p[i].pid = i+1;
}
// calculate waiting time and turnaround time
p[0].waiting_time = 0;
for(i=1; i<n; i++) {
p[i].waiting_time = p[i-1].waiting_time + p[i-1].burst_time;
}
for(i=0; i<n; i++) {
p[i].turnaround_time = p[i].waiting_time + p[i].burst_time;
avg_waiting_time += p[i].waiting_time;
avg_turnaround_time += p[i].turnaround_time;
}
// print result
printf("\nProcess\tArrival Time\tBurst Time\tWaiting Time\tTurnaround Time\n");
for(i=0; i<n; i++) {
printf("%d\t\t%d\t\t%d\t\t%d\t\t%d\n", p[i].pid, p[i].arrival_time, p[i].burst_time, p[i].waiting_time, p[i].turnaround_time);
}
avg_waiting_time /= n;
avg_turnaround_time /= n;
printf("Average Waiting Time: %f\n", avg_waiting_time);
printf("Average Turnaround Time: %f\n", avg_turnaround_time);
return 0;
}
```
短作业优先算法(SJF):
```c
#include <stdio.h>
#define MAX 10
struct Process {
int pid;
int arrival_time;
int burst_time;
int waiting_time;
int turnaround_time;
int is_completed;
};
int main() {
struct Process p[MAX];
int n, i, j;
float avg_waiting_time = 0, avg_turnaround_time = 0;
printf("Enter the number of processes: ");
scanf("%d", &n);
for(i=0; i<n; i++) {
printf("Enter arrival time and burst time for Process %d: ", i+1);
scanf("%d %d", &p[i].arrival_time, &p[i].burst_time);
p[i].pid = i+1;
p[i].is_completed = 0;
}
int time = 0, completed = 0;
while(completed != n) {
int shortest = -1;
for(i=0; i<n; i++) {
if(!p[i].is_completed && p[i].arrival_time <= time) {
if(shortest == -1 || p[i].burst_time < p[shortest].burst_time) {
shortest = i;
}
}
}
if(shortest != -1) {
p[shortest].waiting_time = time - p[shortest].arrival_time;
p[shortest].turnaround_time = p[shortest].waiting_time + p[shortest].burst_time;
avg_waiting_time += p[shortest].waiting_time;
avg_turnaround_time += p[shortest].turnaround_time;
p[shortest].is_completed = 1;
completed++;
time += p[shortest].burst_time;
} else {
time++;
}
}
// print result
printf("\nProcess\tArrival Time\tBurst Time\tWaiting Time\tTurnaround Time\n");
for(i=0; i<n; i++) {
printf("%d\t\t%d\t\t%d\t\t%d\t\t%d\n", p[i].pid, p[i].arrival_time, p[i].burst_time, p[i].waiting_time, p[i].turnaround_time);
}
avg_waiting_time /= n;
avg_turnaround_time /= n;
printf("Average Waiting Time: %f\n", avg_waiting_time);
printf("Average Turnaround Time: %f\n", avg_turnaround_time);
return 0;
}
```
时间片轮转算法(RR):
```c
#include <stdio.h>
#define MAX 10
struct Process {
int pid;
int arrival_time;
int burst_time;
int remaining_time;
int waiting_time;
int turnaround_time;
int is_completed;
};
int main() {
struct Process p[MAX];
int n, i, j, time_quantum;
float avg_waiting_time = 0, avg_turnaround_time = 0;
printf("Enter the number of processes: ");
scanf("%d", &n);
for(i=0; i<n; i++) {
printf("Enter arrival time and burst time for Process %d: ", i+1);
scanf("%d %d", &p[i].arrival_time, &p[i].burst_time);
p[i].pid = i+1;
p[i].remaining_time = p[i].burst_time;
p[i].is_completed = 0;
}
printf("Enter time quantum: ");
scanf("%d", &time_quantum);
int time = 0, completed = 0;
while(completed != n) {
for(i=0; i<n; i++) {
if(!p[i].is_completed && p[i].arrival_time <= time) {
int execute_time = time_quantum;
if(p[i].remaining_time < execute_time) {
execute_time = p[i].remaining_time;
}
p[i].remaining_time -= execute_time;
time += execute_time;
if(p[i].remaining_time == 0) {
p[i].waiting_time = time - p[i].arrival_time - p[i].burst_time;
if(p[i].waiting_time < 0) {
p[i].waiting_time = 0;
}
p[i].turnaround_time = p[i].waiting_time + p[i].burst_time;
avg_waiting_time += p[i].waiting_time;
avg_turnaround_time += p[i].turnaround_time;
p[i].is_completed = 1;
completed++;
}
}
}
}
// print result
printf("\nProcess\tArrival Time\tBurst Time\tWaiting Time\tTurnaround Time\n");
for(i=0; i<n; i++) {
printf("%d\t\t%d\t\t%d\t\t%d\t\t%d\n", p[i].pid, p[i].arrival_time, p[i].burst_time, p[i].waiting_time, p[i].turnaround_time);
}
avg_waiting_time /= n;
avg_turnaround_time /= n;
printf("Average Waiting Time: %f\n", avg_waiting_time);
printf("Average Turnaround Time: %f\n", avg_turnaround_time);
return 0;
}
```
优先级调度算法:
```c
#include <stdio.h>
#define MAX 10
struct Process {
int pid;
int arrival_time;
int burst_time;
int priority;
int waiting_time;
int turnaround_time;
int is_completed;
};
int main() {
struct Process p[MAX];
int n, i, j;
float avg_waiting_time = 0, avg_turnaround_time = 0;
printf("Enter the number of processes: ");
scanf("%d", &n);
for(i=0; i<n; i++) {
printf("Enter arrival time, burst time and priority for Process %d: ", i+1);
scanf("%d %d %d", &p[i].arrival_time, &p[i].burst_time, &p[i].priority);
p[i].pid = i+1;
p[i].is_completed = 0;
}
int time = 0, completed = 0;
while(completed != n) {
int highest_priority = -1, index = -1;
for(i=0; i<n; i++) {
if(!p[i].is_completed && p[i].arrival_time <= time) {
if(p[i].priority > highest_priority) {
highest_priority = p[i].priority;
index = i;
}
}
}
if(index != -1) {
p[index].waiting_time = time - p[index].arrival_time;
p[index].turnaround_time = p[index].waiting_time + p[index].burst_time;
avg_waiting_time += p[index].waiting_time;
avg_turnaround_time += p[index].turnaround_time;
p[index].is_completed = 1;
completed++;
time += p[index].burst_time;
} else {
time++;
}
}
// print result
printf("\nProcess\tArrival Time\tBurst Time\tPriority\tWaiting Time\tTurnaround Time\n");
for(i=0; i<n; i++) {
printf("%d\t\t%d\t\t%d\t\t%d\t\t%d\t\t%d\n", p[i].pid, p[i].arrival_time, p[i].burst_time, p[i].priority, p[i].waiting_time, p[i].turnaround_time);
}
avg_waiting_time /= n;
avg_turnaround_time /= n;
printf("Average Waiting Time: %f\n", avg_waiting_time);
printf("Average Turnaround Time: %f\n", avg_turnaround_time);
return 0;
}
```
进程调度算法;先来先服务调度算法、短作业优先调度算法、时间片轮转调度算法流程图
以下是三种进程调度算法的流程图:
1. 先来先服务调度算法(FCFS):
![FCFS](https://img-blog.csdnimg.cn/20210711160153185.png)
2. 短作业优先调度算法(SJF):
![SJF](https://img-blog.csdnimg.cn/20210711160418471.png)
3. 时间片轮转调度算法(RR):
![RR](https://img-blog.csdnimg.cn/20210711160754691.png)
以上三种调度算法是操作系统中常用的进程调度算法,在实际应用中根据不同场景选择不同的算法可以提高系统的性能和效率。
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