Stuff Goes Bad:Erlang In Anger

Processes

Trying to get a global view of processes is helpful when trying to assess how much work is being done in the VM in terms of tasks. A general good practice in Erlang is to use processes for truly concurrent activities — on web servers, you will usually get one process per request or connection, and on stateful systems, you may add one process per-user — and therefore the number of processes on a node can be used as a metric for load.
Most tools mentioned in section 5.1 will track them in one way or another, but if the process count needs to be done manually, calling the following expression is enough:

查看全局进程总数对了解VM负荷非常有帮助。一个良好的Erlang实践就是为每一个并发的活动都派生出一个进程来处理--对于web服务器，每一个请求或连接就是一个进程，在保存状态的(statefull)系统中，你可能会为每一个用户都派生一个进程，因此可以把节点上的总进程数做为负载指标。
章节5.1中提到的大部分工具都能以不同的方式来追踪它们，但如果手动来计算进程数，你只需要使用下来这个函数就足够了：

--------------------------------------------
1> length(processes()).
56535
-------------------------------------------
Tracking this value over time can be extremely helpful to try and characterize load or detect process leaks, along with other metrics you may have around.

全程追踪这个指标会对衡量负载大小或侦察进程泄露，都非常有用，当然也可能需要结合其它指标来一起诊断。