The Instruments app comes with some great built-in tools that can be used to profile applications. While this is great, sometimes you might need something more tailor-made. Since Xcode 10, you can create your own Instruments Packages to profile your apps. Custom Instruments can use special logging that you add in your app through the os_signpost APIs to keep track of certain processes in your app while collecting interesting data about it. In this section, you will learn how you can add signpost logging to your app as a lightweight mechanism to measure performance in your app. Then, you'll learn how to take this data and funnel it through your own custom Instruments Package.