ftrace

-- ref . http://elinux.org/Ftrace

-- 紀錄開始到結束的時間 echo funcgraph-abstime > trace_options

-- closing bracket 顯示 function name echo funcgraph-tail > trace_options

-- echo __do_fault > set_graph_function 說明: If you want to trace only one function and all of its children, you just have to echo its name into set_graph_function: (function_graph 必須打開)

• find out what is happening inside the kernel at a particular location of the application, these two files come in handy.
  • https://lwn.net/Articles/366796/