进程之间的预定义抢占点 [英] predefined preemption points among processes
问题描述
我分叉了许多子进程，并为每个子进程分配了优先级和核心.流程A的执行时间为3秒，流程B的执行时间为6秒.我希望它们以这样一种方式执行:较高优先级的进程应仅在预定义的点抢占较低优先级的进程，并尝试通过信号量来实现.我在两个进程中都使用了相同的代码片段，但两个代码中的数组值都不相同.
I have forked many child processes and assigned priority and core to each of them. Porcess A executes at period of 3 sec and process B at a period of 6 sec. I want them to execute in such a way that the higher priority processes should preempt lower priority ones only at predefined points and tried to acheive it with semaphores. I have used this same code snippets within the 2 processes with different array values in both.
'bubblesort_desc()'对数组进行降序排序并打印. "bubblesort_asc()"以升序排序并打印.
'bubblesort_desc()' sorts the array in descending order and prints it. 'bubblesort_asc()' sorts in ascending order and prints.
while(a<3)
{
printf("time in sort1.c: %d %ld\n", (int)request.tv_sec, (long int)request.tv_nsec);
int array[SIZE] = {5, 1, 6 ,7 ,9};
semaphore_wait(global_sem);
bubblesort_desc(array, SIZE);
semaphore_post(global_sem);
semaphore_wait(global_sem);
bubblesort_asc(array, SIZE);
semaphore_post(global_sem);
semaphore_wait(global_sem);
a++;
request.tv_sec = request.tv_sec + 6;
request.tv_nsec = request.tv_nsec; //if i add 1ms here like an offset to the lower priority one, it works.
semaphore_post(global_sem);
semaphore_close(global_sem); //close the semaphore file
//sleep for the rest of the time after the process finishes execution until the period of 6
clk = clock_nanosleep(CLOCK_MONOTONIC, TIMER_ABSTIME, &request, NULL);
if (clk != 0 && clk != EINTR)
printf("ERROR: clock_nanosleep\n");
}
无论何时同时激活两个进程，我都会得到这样的输出.例如，以6、12，..
I get the output like this whenever two processes get activated at the same time. For example at time units of 6, 12,..
time in sort1.c: 10207 316296689
time now in sort.c: 10207 316296689
9
99
7
100
131
200
256
6
256
200
5
131
100
99
1
1
5
6
7
9
在打印一组排序的列表时，一个进程不应该抢占另一个进程.但这似乎没有信号灯.我根据此链接定义了信号灯: http://linux.die.net/man/3/pthread_mutexattr_init
One process is not supposed to preempt the other while one set of sorted list is printing. But it's working as if there are no semaphores. I defined semaphores as per this link: http://linux.die.net/man/3/pthread_mutexattr_init
有人可以告诉我原因吗?有没有比信号量更好的选择?
Can anyone tell me what can be the reason for that? Is there a better alternative than semaphores?
推荐答案
它的printf导致输出模棱两可.如果打印的结果中没有'\ n'，那么我们将获得更准确的结果.但是，对于实时应用程序，最好避免使用printf语句.我使用trace-cmd和kernelshark可视化了进程的行为.
Its printf that's causing the ambiguous output. If the results are printed without '\n' then we get a more accurate result. But its always better to avoid printf statements for real time applications. I used trace-cmd and kernelshark to visualize the behaviour of the processes.
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