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

Debugging and troubleshooting Java applications can be challenging when major code modifications are not possible. This article explores various performance tracing and profiling tools that can be used on existing versions of software. BTrace is a tool for understanding Java application behavior by compiling and dynamically inserting Java code into running applications, allowing developers to hook into execution paths and Java runtime components. async-profiler is an open-source, low-overhead profiler suitable for production systems that measures CPU cycles, cache hits/misses, and Java heap memory allocations. jstack is a standard tool shipped with the JDK that prints Java stack traces for running applications and can be used against core files and remote servers. These tools provide valuable insights into application behavior and help solve difficult problems when major code modifications are not feasible.