Linux 下绑定进程到 CPU

1 GLibc API

       #include <sched.h>

       int sched_setaffinity(pid_t pid, unsigned int cpusetsize,
                             cpu_set_t *mask);

       int sched_getaffinity(pid_t pid, unsigned int cpusetsize,
                             cpu_set_t *mask);

Example:

    unsigned int cpu_mask;
    unsigned int pid = 1;
    unsigned int mask = 0x1;    // 绑定到 CPU0，0x2 则绑定到 CPU1

    if (sched_getaffinity (pid, 4, &mask) < 0)
        fprintf (stderr, "failed to get cpu affinity: %s\n", strerror (errno));
    else
    {
        printf ("setting cpu affinity of pid=%d to %x\n", pid, cpu_mask);
        if (sched_setaffinity (pid, 4, &cpu_mask) < 0)
            fprintf (stderr, "failed to get cpu affinity: %s\n", strerror (errno));
        else
            if (sched_getaffinity (pid, 4, &mask) < 0)
                fprintf (stderr, "failed to get cpu affinity: %s\n", strerror (errno));
            else
                printf ("cpu affinity of pid=%d is %x\n", pid, mask);
    }

Other macros to manipulate the bitset (set, reset bits):

       void CPU_CLR(int cpu, cpu_set_t *set);
       int CPU_ISSET(int cpu, cpu_set_t *set);
       void CPU_SET(int cpu, cpu_set_t *set);
       void CPU_ZERO(cpu_set_t *set);

Reference:

• http://www.gnu.org/software/libc/manual/html_node/CPU-Affinity.html

2 Kernel interface (CPU Sets)

运行一个无限循环程序 setaffinity_test (pid = 22580)，top 的输出为：

......
Cpu0 : 24.1%us, 0.3%sy, 0.0%ni, 96.4%id, 0.0%wa, 0.0%hi, 0.0%si, 0.0%st
Cpu1 : 77.8%us, 0.0%sy, 0.0%ni, 0.0%id, 0.0%wa, 0.0%hi, 0.0%si, 0.0%st
Mem:   2033068k total, 1120456k used,   912612k free,    17348k buffers
Swap:        0k total,        0k used,        0k free,   125876k cached
PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+COMMAND 
22580 comcat    25   0 1496 312 252 R 100 0.0   2:54.74 setaffinity_test
......

其 status 为：

$ cat /proc/22580/status | grep allow
Cpus_allowed:   03                 ----------> 可运行于 CPU0 和 CPU1
Mems_allowed:   1

$ mkdir /dev/cpuset
$ mount -t cpuset x /dev/cpuset
$ cd /dev/cpuset
$ mkdir my_cpuset && cd my_cpuset          # 创建自己的设置
$ echo 1 > cpus                                 # 绑定到 CPU1
$ echo 0 > mems
$ echo 22580 > tasks                        # 让 pid 为 22580 的进程绑定到 CPU1

cpuset 设置后，top 的输出为：

......
Cpu0 : 3.3%us, 0.3%sy, 0.0%ni, 96.4%id, 0.0%wa, 0.0%hi, 0.0%si, 0.0%st
Cpu1 : 100%us, 0.0%sy, 0.0%ni, 0.0%id, 0.0%wa, 0.0%hi, 0.0%si, 0.0%st
Mem:   2033068k total, 1120456k used,   912612k free,    17348k buffers
Swap:        0k total,        0k used,        0k free,   125876k cached
PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+COMMAND 
22703 comcat    25   0 1496 312 252 R 100 0.0   2:54.74 setaffinity_test
......

此时其 status 为：

$ cat /proc/22580/status | grep allow
Cpus_allowed:   02                 ----------> 只可运行于 CPU1
Mems_allowed:   1

3 Reference

• http://www.bullopensource.org/cpuset/
• http://www.mjmwired.net/kernel/Documentation/cpusets.txt
• http://www.mjmwired.net/kernel/Documentation/cpu-hotplug.txt