📅  最后修改于: 2023-12-03 14:54:48.315000             🧑  作者: Mango
UGC NET CS 2014 年 12 月 - II 中的问题 24 关于操作系统的问题,它涉及到进程调度和死锁问题。针对该问题,程序员需要了解以下内容:
进程调度是操作系统的一项重要功能,它的主要目的是合理地利用 CPU 和系统资源,保证不同进程之间的公平性和效率。
常见的进程调度算法包括:
需要根据系统的实际情况和应用场景,选择合适的进程调度算法,并根据不同进程之间的状态和优先级,采取相应的调度策略。
死锁是指系统中两个或多个进程,彼此都在等待对方完成某些操作而无法继续执行下去,导致系统整体卡住的现象。死锁可能会导致系统崩溃或变得不稳定。
常见的死锁预防和避免方法包括:
需要对系统中的进程或线程,进行合理的调度和资源分配,以避免死锁的发生。
以下是一个简单的进程调度和死锁判断的代码实现(Python):
# 进程调度算法
class Process:
def __init__(self, id, arrival_time, burst_time, priority):
self.id = id
self.arrival_time = arrival_time
self.burst_time = burst_time
self.priority = priority
# 先来先服务调度算法
def fcfs(processes):
processes = sorted(processes, key=lambda x: x.arrival_time)
current_time = 0
for process in processes:
current_time += process.burst_time
return current_time
# 短作业优先调度算法
def sjf(processes):
processes = sorted(processes, key=lambda x: x.burst_time)
current_time = 0
for process in processes:
current_time += process.burst_time
return current_time
# 优先级调度算法
def priority(processes):
processes = sorted(processes, key=lambda x: x.priority)
current_time = 0
for process in processes:
current_time += process.burst_time
return current_time
# 时间片轮转调度算法
def rr(processes, quantum):
current_time = 0
while True:
done = True
for process in processes:
if process.burst_time > 0:
done = False
if process.burst_time > quantum:
current_time += quantum
process.burst_time -= quantum
else:
current_time += process.burst_time
process.burst_time = 0
if done == True:
break
return current_time
# 死锁检测
def is_deadlock(locks, resources):
work = resources.copy()
finish = [False] * len(locks)
while True:
found = False
for i in range(len(locks)):
if finish[i] == False and all([work[j] >= locks[i][j] for j in range(len(resources))]):
work = [work[j] + resources[j][i] for j in range(len(resources))]
finish[i] = True
found = True
if not found:
break
return all(finish)
# 测试代码
if __name__ == '__main__':
# 进程调度测试用例
processes = [Process(1, 0, 6, 5), Process(2, 2, 2, 4), Process(3, 4, 3, 3), Process(4, 6, 4, 2), Process(5, 8, 8, 1)]
print('FCFS:', fcfs(processes))
print('SJF:', sjf(processes))
print('Priority:', priority(processes))
print('RR:', rr(processes, 2))
# 死锁测试用例
locks = [[1, 0, 0], [1, 0, 1], [0, 1, 0]]
resources = [[1, 0, 0], [1, 0, 1], [0, 1, 0]]
print('Deadlock:', is_deadlock(locks, resources))
代码片段中,实现了常见的进程调度算法和死锁预防方法,程序员可以根据实际需求,进行相应的修改和调试。