[$] Unifying kernel tracing

Steven Rostedt has been a part of the Linux kernel tracing community formost of its existence, it seems. He was the developer of ftrace,which was one of the early mainline additions for tracing. There are nowmany tracing facilities in the kernel. At the 2019Open Source Summit Europe in Lyon, France, Rostedt wanted to present an ideathat he has been thinking about for a long time: a unified tracing platformto provide access to all of the kernel tracing facilities from user-space applications.