Here are some tips to measure the performance of a React Native app:

• Use performance monitoring tools: Tools such as React Native Debugger, React-Native-Perf-Monitor, and Flipper can give you detailed information about the performance of your app, including CPU and memory usage, frame rate, and other metrics.
• Measure app startup time: The time it takes for your app to start up can have a significant impact on the user experience. You can use performance monitoring tools to measure the startup time of your app and identify areas that can be optimized.
• Monitor the frame rate: A low frame rate can cause the app to appear slow and unresponsive. Use performance monitoring tools to measure the frame rate of your app and identify areas where performance can be improved.
• Measure the time it takes for the app to render: A slow rendering time can also cause the app to appear slow and unresponsive. Use performance monitoring tools to measure the rendering time of your app and identify areas where performance can be improved.
• Monitor network performance: Network performance can have a significant impact on the user experience, especially in apps that rely heavily on network requests. Use performance monitoring tools to measure network performance, including the time it takes for requests to complete and the amount of data being transferred.
• Monitor memory usage: Memory leaks can cause the app to crash or become unresponsive. Use performance monitoring tools to measure memory usage and identify areas where memory leaks may be occurring.
• Test on multiple devices: It is important to test the performance of your app on a variety of different devices, including older and lower-end devices, to ensure that it performs well across a wide range of hardware.
• Use Redux-devtools: It's a powerful tool that can help you optimize your Redux-based apps, it gives you a lot of information about the app's state and how it changes over time.
• Use profilers: Xcode and Chrome DevTools provide a built-in performance profiler that can help you identify and fix performance bottlenecks in your React Native app.
• Average your benchmarking measures over several tests and keep the same condition for every measure.
  
  These are just a few tips to measure the performance of a React Native app. It is important to use a combination of different tools and techniques to get a comprehensive understanding of the app's performance and identify areas that can be improved.