Linux load

用top或者uptime命令会显示一个系统最近1分钟、5分钟、15分钟的load average的值；根据uptime命令的说明，其含义是：

System load averages is the average number of processes that are either in a runnable or uninterruptable state. A process in a runnable state is either using the CPU or waiting to use the CPU. A process in uninterruptable state is waiting for some I/O access, eg waiting for disk. The averages are taken over the three time intervals. Load averages are not normalized for the number of CPUs in a system, so a load average of 1 means a single CPU system is loaded all the time while on a 4 CPU system it means it was idle 75% of the time.

大致可以这样理解：对于一个总共n核的系统，其负载为100%时，load average大约为n，负载为50%时，load average就为n/2。

可以看看老外写的关于load average的介绍：http://blog.scoutapp.com/articles/2009/07/31/understanding-load-averages