MySQL的cpu iowait值，<=1/(number of cores)。例如，如果是8核的，io wait 应<=12%。

"Monitor DB CPU IO wait value, which can not be higher than 1/number of cores. For example, if 8 cores, IO wait should be less than 12%."

参考资料

http://*.com/questions/2832912/how-can-set-timestamp-be-a-slow-query