36.6. 显示进程的调度策略和相关属性

流程

1. 创建 sched_timeslice.c 源文件，并在文本编辑器中打开该文件。

   $ {EDITOR} sched_timeslice.c

2. 将以下行添加到 sched_timeslice.c 文件中。

   #define _GNU_SOURCE
   #include <unistd.h>
   #include <stdio.h>
   #include <stdlib.h>
   #include <string.h>
   #include <time.h>
   #include <linux/unistd.h>
   #include <linux/kernel.h>
   #include <linux/types.h>
   #include <sys/syscall.h>
   #include <pthread.h>
   
   #define gettid() syscall(__NR_gettid)
   
   #define SCHED_DEADLINE    6
   
   /* XXX use the proper syscall numbers */
   #ifdef __x86_64__
   #define __NR_sched_setattr        314
   #define __NR_sched_getattr        315
   #endif
   
   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;
   };
   
   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);
   }
   
   int main (int argc, char **argv)
   {
        struct sched_attr attr;
        unsigned int flags = 0;
        int ret;
   
        ret = sched_getattr(0, &attr, sizeof(attr), flags);
        if (ret < 0) {
            perror("sched_getattr");
            exit(-1);
        }
   
        printf("main thread pid=%ld\n", gettid());
        printf("main thread policy=%ld\n", attr.sched_policy);
        printf("main thread nice=%ld\n", attr.sched_nice);
        printf("main thread priority=%ld\n", attr.sched_priority);
        printf("main thread runtime=%ld\n", attr.sched_runtime);
        printf("main thread deadline=%ld\n", attr.sched_deadline);
        printf("main thread period=%ld\n", attr.sched_period);
   
        return 0;
   }

3. 编译 sched_timeslice.c 文件。

   $ gcc sched_timeslice.c -o sched_timeslice

4. 检查 sched_timeslice 程序的输出。

   $ ./sched_timeslice
   main thread pid=321716
   main thread policy=6
   main thread nice=0
   main thread priority=0
   main thread runtime=1000000
   main thread deadline=9000000
   main thread period=10000000