System performance tuning is always a critical issue for the operating systems. When it comes to the Linux kernel, the system administrators and developers have several tools depending on the types of the issues and the subsystems, and perf is probably one of the most famous tools. In the beginning, perf is used to read the performance monitoring units, the special registers in CPU. With the development of Linux kernel, perf starts to support various kernel events. Since perf only does sampling instead of recording all events, the impact to the system is low. Besides event sampling and recording, perf also provides the various tools to analyze or visualize the events, so the developers can have an overview of the system before jumping into the details. This talk will introduce the system events used by perf and the commands. A short demo will also be presented so that the audience will know how it works.