Nginx性能优化CPU参数worker_cpu_affinity使用说明
官方说明：http://wiki.nginx.org/NginxHttpMainModule#worker_cpu_affinit引用worker_cpu_affinity
Syntax: worker_cpu_affinity cpumask [cpumask...]
Default: none
Linux only.
With this option you can bind the worker process to a CPU, it calls sched_setaffinity().
For example,
worker_processes 4;
worker_cpu_affinity 0001 0010 0100 1000;
Bind each worker process to one CPU only.
worker_processes 2;
worker_cpu_affinity 0101 1010;
Bind the first worker to CPU0/CPU2, bind the second worker to CPU1/CPU3. This is suitable for HTT.
一个服务器为Q9300单cpu，4核心，于是可以直接用官方的配置：worker_cpu_affinity 0001 0010 0100 1000;
效果如下，看起来每个cpu核心都比较平均：
Tasks: 238 total, 1 running, 237 sleeping, 0 stopped, 0 zombie
Cpu0 : 0.3%us, 0.3%sy, 0.0%ni, 94.2%id, 5.2%wa, 0.0%hi, 0.0%si, 0.0%st
Cpu1 : 0.3%us, 0.0%sy, 0.0%ni, 96.2%id, 0.6%wa, 0.6%hi, 2.2%si, 0.0%st
Cpu2 : 0.3%us, 0.0%sy, 0.0%ni, 93.5%id, 5.5%wa, 0.0%hi, 0.6%si, 0.0%st
Cpu3 : 0.0%us, 0.0%sy, 0.0%ni, 96.5%id, 3.5%wa, 0.0%hi, 0.0%si, 0.0%st
Mem: 8119372k total, 3641940k used, 4477432k free, 504900k buffers
Swap: 8385888k total, 10664k used, 8375224k free, 2407512k cached
本站所在VPS的CPU为Intel(R) Xeon(R) CPU E5520 @ 2.27GHz x 2，因此写为：
worker_cpu_affinity 01 10;
若要2核CPU开4进程，那么可以写为：
worker_cpu_affinity 01 10 01 10;
2核是 01，四核是0001，8核是00000001，有多少个核，就有几位数，1表示该内核开启，0表示该内核关闭。
worker_processes最多开启8个，8个以上性能提升不会再提升了，而且稳定性变得更低，所以8个进程够用了。