Tools for analyzing Java performance when you can’t modify your app

This article discusses various performance tracing and profiling tools for Java applications when major code modifications are not possible. BTrace is a tool that compiles and dynamically inserts Java code into running applications, allowing developers to hook into execution paths of their apps. async-profiler is an open-source profiler designed for low overhead and suitable for running in production systems. It uses performance events and HotSpot-specific APIs to measure CPU cycles, cache hits/misses, and Java heap memory allocations. jstack prints Java stack traces for a running Java app and can be run against core files and remote servers. These tools provide valuable insights into the behavior of Java applications when debugging is not an option.