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Tag Archives: JVM

Power of Java MemoryMapped File

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Power of Java MemoryMapped File In JDK 1.4 an interesting feature of Memory mapped file was added to Java, which allows to map any file to OS memory for efficient reading. A memory mapped file can be used to develop an  IPC type of solution. This article is an experiment with memory mapped file to create IPC. Some details about ...

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How to create a memory leak

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This is going to be a rather evil post – something you will be googling when you really wish to make someone’s life a misery. In the world of Java development memory leaks are just the type of bugs you would introduce in this case. Days or even weeks of sleepless nights in the office are guaranteed for your victim. ...

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HotSpot GC Thread CPU footprint on Linux

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The following question will test your knowledge on garbage collection and high CPU troubleshooting for Java applications running on Linux OS. This troubleshooting technique is especially crucial when investigating excessive GC and / or CPU utilization. It will assume that you do not have access to advanced monitoring tools such as Compuware dynaTrace or even JVisualVM. Future tutorials using such ...

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Monitoring Key JVM Characteristics with Groovy, JMX, and RuntimeMXBean

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Since J2SE 5, Platform MBeans have been available that allow some key characteristics regarding the JVM to be monitored and (even managed in some cases) via JMX. In addition, many JVM-based applications add their own JMX-enabled features for monitoring and management. In the blog post Groovy, JMX, and the Attach API, I looked at how to display many of the ...

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OpenJPA: Memory Leak Case Study

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This article will provide the complete root cause analysis details and resolution of a Java heap memory leak (Apache OpenJPA leak) affecting an Oracle Weblogic server 10.0 production environment. This post will also demonstrate the importance to follow the Java Persistence API best practices when managing the javax.persistence.EntityManagerFactory lifecycle.             Environment specifications Java EE server: ...

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Hunting down memory leaks: a case study

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A week ago I was asked to fix a problematic webapp suffering from memory leaks. How hard can it be, I thought – considering that I have both seen and fixed hundreds of leaks over the past two years or so. But this one proved to be a challenge. 12 hours later I had discovered no less than five leaks ...

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Analysing a Java Core Dump

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In this post, I will show you how you can debug a Java core file to see what caused your JVM to crash. I will be using a core file I generated in my previous post: Generating a Java Core Dump. There are different ways you can diagnose a JVM crash, listed below: The hs_err_pid log file When a fatal ...

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How aggressive is method inlining in JVM?

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Ctrl + Alt + M is used in IntelliJ IDEA to extract method. Ctrl + Alt + M. It’s as simple as selecting a piece of code and hitting this combination. Eclipse also has it. I hate long methods. To the point where this smells way too long for me:                 public void ...

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Java 8: From PermGen to Metaspace

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As you may be aware, the JDK 8 Early Access is now available for download. This allows Java developers to experiment with some of the new language and runtime features of Java 8. One of these features is the complete removal of the Permanent Generation (PermGen) space which has been announced by Oracle since the release of JDK 7. Interned ...

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QOTD: Java Thread vs. Java Heap Space

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The following question is quite common and is related to OutOfMemoryError: unable to create new native thread problems during the JVM thread creation process and the JVM thread capacity. This is also a typical interview question I ask to new technical candidates (senior role). I recommend that you attempt to provide your own response before looking at the answer.   ...

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