Question

当前，我正在运行Ubuntu 16.04，Linux内核版本为4.15，并且我试图找出linux最后期限调度程序的用途。我遵循official website中发布的示例代码，该示例代码将截止日期和期限设置为30ms。以下是我的代码：

    #include <time.h>
    #include <errno.h>
    #include <stdint.h>
    #include <sys/stat.h>
    #include <fcntl.h>
    #include <pthread.h>
    #include <linux/kernel.h>
    #include <linux/types.h>
    #include <syscall.h>
    #include <math.h>
    #include <sched.h>
    #include <sys/ioctl.h>
    #include <sys/types.h>
    #include <sys/mman.h>
    #include <sched.h>
    #include <linux/sched.h>
    #include <signal.h>
    #include <execinfo.h>
    #include <getopt.h>
    #include <sys/sysinfo.h>

    #define __NR_sched_setattr   314
    #define __NR_sched_getattr   315

    #define RTIME long long int
    #define rt_printk printf

    #define SCHED_DEADLINE  6

    struct sched_attr {
      __u32 size;

      __u32 sched_policy;
      __u64 sched_flags;

      /* SCHED_NORMAL, SCHED_BATCH */
      __s32 sched_nice;

      /* SCHED_FIFO, SCHED_RR */
      __u32 sched_priority;

      /* SCHED_DEADLINE (nsec) */
      __u64 sched_runtime;
      __u64 sched_deadline;
      __u64 sched_period;
    } sched_attr_t;

    int sched_setattr(pid_t pid, const struct sched_attr *attr, unsigned int flags){

        return syscall(__NR_sched_setattr, pid, attr, flags);
    }


    int sched_getattr(pid_t pid,struct sched_attr *attr,unsigned int size, unsigned int flags){

        return syscall(__NR_sched_getattr, pid, attr, size, flags);
    }


    #define gettid() syscall(__NR_gettid) // for gettid

    static volatile int done;

    void *run_deadline(void *data){

        struct sched_attr attr;
        int x = 0, ret;
        unsigned int flags = 0;

        printf("deadline thread start %ld\n", gettid());

        attr.size = sizeof(attr);
        attr.sched_flags = 0;
        attr.sched_nice = 0;
        attr.__sched_priority = 0;

        attr.sched_policy = SCHED_DEADLINE;
        attr.sched_period = 30 * 1000 * 1000;
        attr.sched_runtime = 10 * 1000 * 1000;
        attr.sched_deadline = 30 * 1000 * 1000;

        ret = sched_setattr(0, &attr, flags);

        if(ret < 0){
            done = 0;
            perror("sched_setattr");
            exit(-1);
        }

        while(!done){
            x++;
        }

        printf("x = %d \n", x);
        return NULL;
    }

    int main(){

        pthread_t thread;

        printf("main thread [%ld] \n", gettid());
        pthread_create(&thread, NULL, run_deadline, NULL);
        sleep(10);
        done = 1;
        pthread_join(thread, NULL);
        printf("main dies [%ld] \n", gettid());

        return 0;
    }

我认为，如果正确设置了截止日期参数，则run_deadline（）中的循环应该每30毫秒开始一次，x的值将为334，直到程序终止。

kay@IET:~/eclipse-workspace/dlsched/Debug$ sudo ./dlsched 
main thread [29485] 
deadline thread start 29486
x = 920417116 
main dies [29485]

但是，我在循环后面添加了一个“ printf”来打印x的值，结果是“ x = 844426336”。似乎循环未按我设置的那样运行。在使用截止时间调度程序之前，是否需要执行任何程序？

我真的对这个问题感到困惑。谁能给我一些提示，建议或类似的东西？

如何使用Linux Deadline Scheduler

0 个答案: