Severin Gehwolf

Thermostat is a monitoring and management tool for Java deployments, allowing users to measure and monitor a host of different performance aspects of their Java applications. Available metrics range from raw CPU and memory usage to operation of the Garbage Collector and JIT compiler through to thread activity and method call/heap profiles. Thermostat provides a GUI view of activity of local and distributed JVMs in a live-view or, alternatively, offline for after-the-fact analysis.

What Thermostat cannot do on its own is track events and record statistics that are specific to a given Java application, at least not unless the application co-operates with it, for example by publishing JMX statistics that Thermostat can read, persist and display in its GUI. However, that's about to change thanks to work Thermostat developers have been doing to integrate Byteman into Thermostat.

Byteman is a tool which can be used to modify the behaviour of Java programs by injecting extra Java code almost anywhere in the program. You don't need to recompile your program or even prepare it in advance in order for this to work. You can specify changes to the program on the command line but, what is more amazing, you can actually use Byteman to change the way a program runs after startup while it is still running.

In this talk we will show how Thermostat can collect and visualize metrics with Byteman's help in order to better understand a specific performance issue in a Java application.

OpenJDK comes with a zero assembler port called Zero. Back in 2009 when Zero was originally developed by Gary Benson, OpenJDK was available only on x86, x86_64 and SPARK. Despite recent JIT ports, such as the AArch64 and ppc/aix port, Zero still remains relevant for many Linux distributions. For example, at Red Hat we build and use the OpenJDK zero variant on PPC/PPC64 and s390/s390x. What's more it's a useful tool for getting new JIT ports built from source using free software.

This talk will give a brief summary what Zero is and how it works. It will cover some of the recently discovered issues with sustaining the Zero port, how we try to catch them early and it will explain our experience with pushing fixes upstream. There will also be examples how this effort benefits the OpenJDK ecosystem as a whole.

Debugging performance problems can be a daunting task, especially when you are short on time and lack proper tools that integrate nicely with your custom application landscape. Thermostat was designed to answer the most interesting questions related to performance measurement and application monitoring. It takes advantage of performance metrics and serviceability features of OpenJDK to provide a holistic view of the system. In this session, attendees will get a chance to see Thermostat in action as it is used to analyse programs, gather data, and debug issues affecting performance and functionality.