December 2017 - java-devroom - lists.fosdem.org

Talk Proposal: The Z Garbage Collector - An Introduction
by Per Liden 01 Dec '17

01 Dec '17

Title: The Z Garbage Collector - An Introduction Abstract: The Z Garbage Collector, also known as ZGC, is a new garbage collector optimized for low latency and very large heaps. We've developed ZGC internally at Oracle so far, but we're now open-sourcing it so as to broaden the base of both contributors and users. It was recently accepted as an official project under OpenJDK where future development will be happening. This talk will give an overview of how ZGC works, how it scales to multi-terabyte heaps and how it maintains very low GC pause times. We'll present the goals, current status and what to expect going forward. We'll also give a quick primer on how to get started using ZGC on your workloads. Time: 25 min works, but 45 min would give us a chance to dive a bit deeper. Speakers: Per Liden and Stefan Karlsson Bios: Per Liden is a member of the HotSpot Garbage Collection team at Oracle, and has been working on JRockit and HotSpot projects for the past 8 years. Per is an OpenJDK Reviewer and the lead for the ZGC project. Stefan Karlsson is a member of the HotSpot Garbage Collection team and has been working on JRockit and HotSpot projects for 13 years. Stefan is an OpenJDK Reviewer and has been working on large projects like the Permgen Removal, G1 Class Unloading, and for the last two years, ZGC.

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Proposal: Hacking the JVM from Java
by Tobias Lindaaker 01 Dec '17

01 Dec '17

I would like to propose a 25 minute talk for the Free Java DevRoom. TITLE: Hacking the JVM from Java = ABSTRACT = The JVM contains many interesting features that are frequently overlooked, not exposed through the Java standard library, or typically only accessible from native code. In this talk we will walk through a few of these features, and how they can be used from plain old java code. For example we will see how to access local variables from calling methods, as well as powerful ways to monitor what the JVM does when executing our code. Free Java allows us access to these features, as well as the ability to contribute towards improving their implementation and make them publicly available to other users. Together we can influence the direction of Java and help get more powerful features into the standard JDK. RECORDING: acceptable under a CC-BY-2.0 license = BIO = Tobias has been with Neo4j since the very beginning, where his Java expertise frequently comes in handy. Even outside of Neo4j, he has a long experience with open source and java development. For example he contributed to rewriting the Jython compiler in order to support Python 2.5. TWITTER URL: https://twitter.com/thobe <https://twitter.com/thobe> WEBSITE / BLOG URL: http://www.thobe.org/ <http://www.thobe.org/> Cheers, Tobias

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Top Ten Metrics for Evaluating your Garbage Collector
by Christine Flood 01 Dec '17

01 Dec '17

Title: Top Ten Metrics for Evaluating your Garbage Collector Abstract: There's an old joke about a new bride who prepares her first big dinner for her new husband. She's making her mother's brisket recipe which starts by cutting the ends off of the roast. Her husband asks her why she cuts the ends off. She says she does it because that's the way her mother always did it. She asks her mother and her mother says "That's the way your grandmother always did it". She asks her grandmother and her grandmother says "That's the only way it would fit in my pan". There's a lot of folklore and myth surrounding Java garbage collection performance, most of which is obsolete, irrelevant to your application, or was never really right in the first place. So how do we evaluate a GC algorithm? We can measure various metrics: end to end run time, maximum pause time, average pause time, percentage of the cpu given to the Java threads, memory footprint, micro benchmarks, ... This talk will focus on ten (give or take) metrics/tools we can use to evaluate garbage collection performance. This isn't a comparison of OpenJDK collectors, it's a discussion of what characteristics are important in a good garbage collector and how to measure them. Speaker: Christine H. Flood is one of the authors of Shenandoah at Red Hat. She has been hacking Garbage Collectors for longer than she cares to admit. She's published academic papers on Shenandoah, G1, and the Parallel Collector and is a Java One Rock star. Time: 25 minutes Recording video and/or audio CC-BY-2.0 license is acceptable.

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Talk Proposal: Class Metadata: A User Guide
by Andrew Dinn 01 Dec '17

01 Dec '17

Title: Class Metadata: A User Guide Abstract: The OpenJDK JVM eats class bytecode and spits out Java heap objects and machine code as part of normal execution. However, the JVM manages more data than just bytecode, Java objects JITted code. In order to manage heap memory and to ensure correct execution, the JVM and JITted code need to retain and, occasionally, interrogate details of the loaded class base. Bytecode is not a very 'efficient' representation for this purpose, nor does it include details of runtime-derived info like class and method implementation dependencies, compile history and JITted code status, or execution profiles. So, the JVM throws away most bytecode after parsing, in its place constructing and maintaining its own 'efficient' in-memory (C++) data structures which model both the loaded class and method base and runtime-derived state. This is what is known as Class Metadata. Class Metadata is a significant component of the Native Memory storage allocated and managed by the JVM, alongside JIT Compiler Metadata, GC Metadata, Thread Metadata, etc. For small applications that don't create a large number of Java objects Metadata can constitute a large portion of a Java application's resident memory set. This talk will begin by describing how to use the jcmd tool to measure summary JVM Native Memory storage costs, including overall Class Metadata costs. It will also show how to use jcmd to obtain a detailed breakdown of the latter costs, splitting the overheads along two axes: firstly, by class; and secondly, dividing per-class costs into separate sub-costs associated with different component subsets of the class model: classes per se, constant pools, methods and annotations. I will go on to explain how Class Metadata is carved out of the memory regions managed by the JVM's Native Memory allocation routines and detail the memory layout of the various C++ types which define the elements of the Class Metadata model, thereby clarifying some of the more detailed statistics available in jcmd output. Real-life use cases will be employed to explain how specific costs arise from code design choices and to suggest how alternative choices might increase or decrease Class Metadata costs. Speaker: Andrew Dinn OpenJDK developer and Byteman Project Lead working at Red Hat Time: 45 min preferred Recording video and/or audio CC-BY-2.0 license is acceptable. regards, Andrew Dinn ----------- Senior Principal Software Engineer Red Hat UK Ltd Registered in England and Wales under Company Registration No. 03798903 Directors: Michael Cunningham, Michael ("Mike") O'Neill, Eric Shander

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Free Java Devroom deadline extended!
by Mario Torre 01 Dec '17

01 Dec '17

Hello everyone! It’s Christmas earlier this year! By popular demand we are excited to extend the deadline for submission to the 10th of December (23:59 CET)! I will shortly update the website, but the new deadline is effective immediately! Cheers, Mario

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