Memory Management: What You Need to Know When Moving to Java 8

Une riche présentation de Mapping Objet Relationnel qui traite le standard JPA et l’implémentation Hibernate en les intégrant avec le frammework IOC spring.

The document discusses Java memory management and garbage collection. It describes the responsibilities of garbage collection as allocating memory, ensuring referenced objects remain in memory, and recovering memory from unreachable objects. It discusses generation collection and the Hotspot memory model with young and old generations. The major garbage collectors are described as serial, parallel, parallel compacting, and concurrent mark-sweep collectors. The document provides examples of VM options and logging output.

Here I discuss about Java programming language and easiest way to solve programming problem. Java basic syntax and their uses are described briefly so that anyone can easily understand within very short time. If anyone follow the slide with proper way,I assure that he or she will find java programming interesting.

This document discusses Java garbage collection. It describes the serial, parallel, and concurrent collectors. The serial collector uses one thread for garbage collection while the parallel collector performs minor collections in parallel. Concurrent collectors like CMS and G1 perform most work concurrently to minimize pauses. The document also discusses selecting collectors based on data size, performance priorities, and pause time requirements. It notes young generation collectors like Copy and PS Scavenge as well as old generation collectors like MarkSweepCompact and ConcurrentMarkSweep.

The very best attackers often use PowerShell to hide their scripts from A/V and application whitelisting technologies using encoded commands and memory-only payloads to evade detection. These techniques thwart Blue Teams from determining what was executed on a target system. However, defenders are catching on, and state-of-the-art detection tools now monitor the command line arguments for powershell.exe either in real-time or from event logs. We need new avenues to remain stealthy in a target environment. So, this talk will highlight a dozen never-before-seen techniques for obfuscating PowerShell command line arguments. As an incident responder at Mandiant, I have seen attackers use a handful of these methods to evade basic command line detection mechanisms. I will share these techniques already being used in the wild so you can understand the value each technique provides the attacker. Updated PowerShell event logging mitigates many of the detection challenges that obfuscation introduces. However, many organizations do not enable this PowerShell logging. Therefore, I will provide techniques that the Blue Team can use to detect the presence of these obfuscation methods in command line arguments. I will conclude this talk by highlighting the public release of Invoke-Obfuscation. This tool applies the aforementioned obfuscation techniques to user-provided commands and scripts to evade command line argument detection mechanisms. --- Daniel Bohannon Daniel Bohannon is an Incident Response Consultant at MANDIANT with over six years of operations and information security experience. His particular areas of expertise include enterprise-wide incident response investigations, host-based security monitoring, data aggregation and anomaly detection, and PowerShell-based attack research and detection techniques. As an incident response consultant, Mr. Bohannon provides emergency services to clients when security breach occur. He also develops new methods for detecting malicious PowerShell usage at both the host- and network-level while researching obfuscation techniques for PowerShell- based attacks that are being used by numerous threat groups. Prior to joining MANDIANT, Mr. Bohannon spent five years working in both IT operations and information security roles in the private retail industry. There he developed operational processes for the automated aggregation and detection of host- and network-based anomalies in a large PCI environment. Mr. Bohannon also programmed numerous tools for host-based hunting while leading the organization’s incident response team. Mr. Bohannon received a Master of Science in Information Security from the Georgia Institute of Technology and a Bachelor of Science in Computer Science from The University of Georgia.

This document introduces ReactJS, a JavaScript library for building user interfaces. It discusses key React concepts like the virtual DOM, which is a JavaScript representation of real DOM elements that allows React to efficiently update the real DOM by comparing it to a new virtual DOM. It also covers one-way data binding in React, where data flows from parent to child components through props, while events flow in the opposite direction. Finally, it emphasizes that in React, everything is a component, and components manage their own state and receive immutable props from parent components.

Leandro Melendez from Grafana k6 starts off by providing a grounding in current expectations of what performance engineering and load testing entail. This session defines the modern challenges developers face, including continuous performance principles, Service Level Objectives (SLOs), and Service Level Indicators (SLIs). It delineates best practices and provides hands-on examples using Grafana k6, an open source modern load testing tool.

For years we’ve been told that the JVM’s amazing optimizers can take your running code and make it “fast” or “as fast as C++” or “as fast as C”…or sometimes “faster than C”. And yet we don’t often see this happen in practice, due in large part to (good and bad) development patterns that have taken hold in the Java world. In this talk, we’ll explore the main reasons why Java code rarely runs as fast as C or C++ and how you can write really bad Java code that the JVM will do a better job of optimizing. We’ll take some popular microbenchmarks and burn them to the ground, monitoring JIT logs and assembly dumps along the way.

This document summarizes key concepts about packages, classes, and the static keyword in Java. It discusses how packages are used to organize classes and prevent naming conflicts. It also explains that the static keyword in Java is used for memory management and that static variables, methods, blocks, and nested classes belong to the class rather than object instances. The document provides examples of how to define packages and use the static keyword with variables, methods, and blocks in Java programs.

Talk built based on several of my trainings: http://www.victorrentea.ro/#training Covers: Clean/Onion/Hexagonal Architecture, Domain Entities, Value Objects, Repository, Extract When it Grows Principle, Dependency Inversion Principle, Clean Code and Design Patterns. These are the backing slides of the talks given at JPoint 2017 and Devoxx PL 2017: https://www.youtube.com/embed/4-4ahz7zDiQ

This session is all about - the mechanism provided by Java Virtual Machine to reclaim heap space from objects which are eligible for Garbage collection.

Java on Kubernetes may seem complicated, but after a bit of YAML and Dockerfiles, you will wonder what all that fuss was. But then the performance of your app in 1 CPU/1 GB of RAM makes you wonder. Learn how JVM ergonomics, CPU throttling, and GCs can help increase performance while reducing costs.

The document discusses using Maven for automation builds. It covers quick starting a Maven project, the Maven lifecycle and phases, dependency and plugin management, and integrating Maven with IDEs like Eclipse. Key points include how to create a basic Maven project, the different Maven directories, common Maven commands, using the Surefire plugin to run tests, and configuring test dependencies.

Webpack is a module bundler that bundles JavaScript files for use in a browser. It takes modules with dependencies and generates static assets representing those modules. The key steps are to specify an entry point, add loaders for file transformations, specify the output bundle, and use plugins like html-webpack-plugin to generate HTML files that link to the bundled scripts. Webpack traverses dependency graphs to bundle assets in an optimized way.

This document provides an introduction to JUnit and Mockito for testing Java code. It discusses how to set up JUnit tests with annotations like @Before, @After, and @Test. It also covers using JUnit assertions and test suites. For Mockito, the document discusses how to create and use mock objects to stub behavior and verify interactions. It provides examples of argument matchers and consecutive stubbing in Mockito.

GraalVMs native-image ermöglicht es, JVM Bytecode direkt in Maschinencode zu übersetzen. Das daraus resultierende Executable benötigt keine JVM zum Laufen, startet schneller und verbraucht weniger Speicher als eine traditionelle JVM-Anwendung – ein Segen für Cloud Computing, bei dem jeder CPU-Cycle und Megabyte an RAM bezahlt werden muss. Wäre es nicht großartig, wenn unser Lieblingsframework, Spring Boot, GraalVM direkt out of the box unterstützen würde? In diesem Talk zeigt Moritz Halbritter, Spring Boot committer, was mit Spring Boot 3 und Spring Framework 6 alles möglich sein wird und erlaubt auch einen Blick unter die Motorhaube, um zu sehen, wie das alles implementiert ist.

This document provides an overview of Java input/output (I/O) concepts including reading from and writing to the console, files, and streams. It discusses different I/O stream classes like PrintStream, InputStream, FileReader, FileWriter, BufferedReader, and how to read/write characters, bytes and objects in Java. The document also introduces new I/O features in Java 7 like try-with-resources for automatic resource management.

This document discusses various tools for monitoring and analyzing metaspace and class metadata in the Java virtual machine. It describes using -XX:+PrintGCDetails to print details of full GC collections including metaspace usage. It also discusses using MBeans, jstat -gc, and VisualVM to monitor memory pools like metaspace and class space. The document further explains using jmap -clstats to view statistics per class loader and GC.class_stats to view statistics on Java class metadata, which both require unlocking diagnostic VM options.

The workshop is based on several Nikita Salnikov-Tarnovski lectures + my own research. The workshop consists of 2 parts. The first part covers: - different Java GCs, their main features, advantages and disadvantages; - principles of GC tuning; - work with GC Viewer as tool for GC analysis; - first steps tuning demo; - comparison primary GCs on Java 1.7 and Java 1.8 The second part covers: - work with Off-Heap: ByteBuffer / Direct ByteBuffer / Unsafe / MapDB; - examples and comparison of approaches; The off-heap-demo: https://github.com/moisieienko-valerii/off-heap-demo

The Java Memory Model defines rules for how threads interact through shared memory in Java. It specifies rules for atomicity, ordering, and visibility of memory operations. The JMM provides guarantees for code safety while allowing compiler optimizations. It defines a happens-before ordering of instructions. The ordering rules and visibility rules ensure threads see updates from other threads as expected. The JMM implementation inserts memory barriers as needed to maintain the rules on different hardware platforms.

This document discusses Java memory monitoring and tuning. It begins by describing the major memory regions in Java including heap, non-heap, code cache and permanent generation. It then discusses monitoring tools like JConsole and JStat. A significant portion discusses changes in Java 8 where the permanent generation was removed and replaced with metaspaces, which are more efficient and no longer cause full garbage collection pauses. The document concludes with examples of metaspace configuration options and monitoring commands.

Are you tired of java.lang.OutOfMemoryError: PermGen space? Then this talk is for you! We'll begin with a crash course in the Java memory model in order to understand what the error message means. Then we'll look at different causes of the error and how to avoid them. We may glance at a few interesting mistakes from the Open Source world. Last but not least you'll learn how you can get rid of java.lang.OutOfMemoryError: PermGen space once and for all.

While most bugs reveal their cause within their stack trace, Java’s OutOfMemoryError is less talkative and therefore regarded as being difficult to debug by a majority of developers. With the right techniques and tools, memory leaks in Java programs can however be tackled like any other programming error. This talks discusses how a JVM stores data, categorizes different types of memory leaks that can occur in a Java program and presents techniques for fixing such errors. Furthermore, we will have a closer look at lambda expressions and their considerable potential of introducing memory leaks when they are used incautiously.

HotSpot 7u40 で導入されたNative Memory Tracking機能についてです。

This document discusses the Java Memory Model (JMM) and how it describes how threads interact through memory in Java. It covers key aspects of the JMM including happens-before ordering, memory barriers, visibility rules, and how final fields and atomic instructions interact with the memory model. It also discusses performance considerations and how different processor architectures implement memory ordering.

The document discusses various aspects of Java memory usage and garbage collection. It describes the Java heap structure, including the young generation, old generation, and survivor spaces. It also discusses object header information, memory addressing, and the impact of architecture (32-bit vs 64-bit) and JVM vendor (Oracle vs IBM) on object sizes. The garbage collection process of marking, sweeping, and compacting is explained.

The document discusses tuning Java for large data workloads. It covers symptoms of memory issues like jobs getting stuck or failing. It then discusses various Java and Hadoop configuration settings to optimize memory usage like mapreduce.child.java.opts and mapreduce.map.memory.mb. Finally, it provides an overview of different garbage collectors in Java and factors like generation sizes and concurrent marking that impact performance.