树莓派提高实时性

首先你可以根据指令 htop ,看到4个cpu

首先有俩个思路，第一种提高这个进程的优先级，使CPU全速运行这个进程，这个是随机分配到某个CPU上，运行

函数原型：

#include 
#include 

int test1(const int pri)
{
  struct sched_param sched ;

  memset (&sched, 0, sizeof(sched)) ;

  if (pri > sched_get_priority_max (SCHED_RR))
    sched.sched_priority = sched_get_priority_max (SCHED_RR) ;
  else
    sched.sched_priority = pri ;

  return sched_setscheduler (0, SCHED_RR, &sched) ;
}

pri= 0 (默认) to 99 (最高)
返回 0，成功； -1， 失败；

函数只需要放在程序的初始化位子，就行；

第二种
将树莓派单独预留出一个CPU，单独的运行这个实时的进程
首先在/boot/cmdline.txt 中末尾添加

isolcpus=x,x为屏蔽的核心 X=3时为树莓派中的最后一个CPU

然后将程序挂载在刚刚禁用的CPU上，使CPU全速运行这个程序

#define __USE_GNU
#include .h>

void test2(){
     cpu_set_t mask;
     CPU_ZERO(&mask);
     CPU_SET(3,&mask);
     if (sched_setaffinity(0,sizeof(mask),&mask)<0){
                printf("affinity set fail!");}
 }

这里需要定义 __USE_GNU
在 sched.h中（片断截取）

#ifdef __USE_GNU
/* Access macros for `cpu_set'.  */
# define CPU_SETSIZE __CPU_SETSIZE
# define CPU_SET(cpu, cpusetp)   __CPU_SET_S (cpu, sizeof (cpu_set_t), cpusetp)
# define CPU_CLR(cpu, cpusetp)   __CPU_CLR_S (cpu, sizeof (cpu_set_t), cpusetp)
# define CPU_ISSET(cpu, cpusetp) __CPU_ISSET_S (cpu, sizeof (cpu_set_t), \
                        cpusetp)
# define CPU_ZERO(cpusetp)   __CPU_ZERO_S (sizeof (cpu_set_t), cpusetp)
# define CPU_COUNT(cpusetp)  __CPU_COUNT_S (sizeof (cpu_set_t), cpusetp)

# define CPU_SET_S(cpu, setsize, cpusetp)   __CPU_SET_S (cpu, setsize, cpusetp)
# define CPU_CLR_S(cpu, setsize, cpusetp)   __CPU_CLR_S (cpu, setsize, cpusetp)
# define CPU_ISSET_S(cpu, setsize, cpusetp) __CPU_ISSET_S (cpu, setsize, \
                               cpusetp)
# define CPU_ZERO_S(setsize, cpusetp)       __CPU_ZERO_S (setsize, cpusetp)
# define CPU_COUNT_S(setsize, cpusetp)      __CPU_COUNT_S (setsize, cpusetp)

# define CPU_EQUAL(cpusetp1, cpusetp2) \
  __CPU_EQUAL_S (sizeof (cpu_set_t), cpusetp1, cpusetp2)
# define CPU_EQUAL_S(setsize, cpusetp1, cpusetp2) \
  __CPU_EQUAL_S (setsize, cpusetp1, cpusetp2)

# define CPU_AND(destset, srcset1, srcset2) \
  __CPU_OP_S (sizeof (cpu_set_t), destset, srcset1, srcset2, &)
# define CPU_OR(destset, srcset1, srcset2) \
  __CPU_OP_S (sizeof (cpu_set_t), destset, srcset1, srcset2, |)
# define CPU_XOR(destset, srcset1, srcset2) \
  __CPU_OP_S (sizeof (cpu_set_t), destset, srcset1, srcset2, ^)
# define CPU_AND_S(setsize, destset, srcset1, srcset2) \
  __CPU_OP_S (setsize, destset, srcset1, srcset2, &)
# define CPU_OR_S(setsize, destset, srcset1, srcset2) \
  __CPU_OP_S (setsize, destset, srcset1, srcset2, |)
# define CPU_XOR_S(setsize, destset, srcset1, srcset2) \
  __CPU_OP_S (setsize, destset, srcset1, srcset2, ^)

# define CPU_ALLOC_SIZE(count) __CPU_ALLOC_SIZE (count)
# define CPU_ALLOC(count) __CPU_ALLOC (count)
# define CPU_FREE(cpuset) __CPU_FREE (cpuset)


/* Set the CPU affinity for a task */
extern int sched_setaffinity (__pid_t __pid, size_t __cpusetsize,
                  const cpu_set_t *__cpuset) __THROW;

/* Get the CPU affinity for a task */
extern int sched_getaffinity (__pid_t __pid, size_t __cpusetsize,
                  cpu_set_t *__cpuset) __THROW;
#endif

所以想使用挂载在CPU上的函数的时候，需要定义 __USE_GNU，也同样的只需要在程序初始化的时候，添加就可以了

俩者也可以同时添加在一起。