cpu亲合度（affinity）设置

可以在linux下使用man sched_setaffinity查看相关使用说明

long sched_setaffinity(pid_t pid, unsigned int len,
                  unsigned long *user_mask_ptr);
long sched_getaffinity(pid_t pid, unsigned int len,
                  unsigned long *user_mask_ptr);

The first system call is used to set the affinity of a process, and the second system call retrieves it.

In either system call, the PID argument is the PID of the process whose mask you wish to set or retrieve. If the PID is set to zero, the PID of the current task is used.

The second argument is the length in bytes of the CPU affinity bitmask, currently four bytes (32 bits). This number is included in case the kernel ever changes the size of the CPU affinity mask and allows the system calls to be forward-compatible with any changes; breaking syscalls is bad form, after all. The third argument is a pointer to the bitmask itself.

Let us look at retrieving the CPU affinity of a task:

unsigned long mask;
unsigned int len = sizeof(mask);
if (sched_getaffinity(0, len, &mask) < 0) {
    perror("sched_getaffinity");
    return -1;
    }
printf("my affinity mask is: %08lx/n", mask);

As a convenience, the returned mask is binary ANDed against the mask of all processors in the system. Thus, processors in your system that are not on-line have corresponding bits that are not set. For example, a uniprocessor system always returns 1 for the above call (bit 0 is set and no others).

Setting the mask is equally easy:

unsigned long mask = 7; /* processors 0, 1, and 2 */
unsigned int len = sizeof(mask);
if (sched_setaffinity(0, len, &mask) < 0) {
    perror("sched_setaffinity");
}

This example binds the current process to the first three processors in the system.