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Tag Archives: JVM

Printing Generated Assembly Code From The Hotspot JIT Compiler

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Sometimes when profiling a Java application it is necessary to understand the assembly code generated by the Hotspot JIT compiler. This can be useful in determining what optimisation decisions have been made and how our code changes can affect the generated assembly code. It is also useful at times knowing what instructions are emitted when debugging a concurrent algorithm to ...

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Garbage Collection in Java (3)

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This follows on from my previous two garbage collection blog posts: Overview of GC in Hotspot. Parallel Garbage Collectors. Concurrent Mark Sweep The parallel garbage collectors in Hotspot are designed to minimise the amount of time that the application spends undertaking garbage collection, which is termed throughput. This isn’t an appropriate tradeoff for all applications – some require individual pauses ...

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Garbage Collection in Java (2)

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Parallel Scavenge Today we cover how Parallel GC works. Specifically this is the combination of running a Parallel Scavenge collector over Eden and the Parallel Mark and Sweep collector over the Tenured generation. You can get this option by passing in -XX:+UseParallelOldGC though its the default on certain machine types. You may want to read my first blog post on ...

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Garbage Collection in Java (1)

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This is the first in a series of posts about Garbage Collection (GC). I hope to be able to cover a bit of theory and all the major collectors in the hotspot virtual machine over the course of the series. This post just explains what garbage collection is and elements common to different collectors. Why should I care? Your Java ...

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GC Memory Visualizer Tutorial – Part1

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As you may have read from past articles, one of the key Java programmer skills to acquire is your ability to understand and assess the health of the JVM such as the Java heap memory footprint along with the garbage collection process. In order to achieve the above goals, all JVM vendors (Oracle, IBM…) provide, via the verbose:gc parameter, a ...

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Reducing memory consumption by 20x

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This is going to be another story sharing our recent experience with memory-related problems. The case is extracted from a recent customer support case, where we faced a badly behaving application repeadedly dying with OutOfMemoryError messages in production. After running the application with Plumbr attached we were sure we were not facing a memory leak this time. But something was ...

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JVM Performance Magic Tricks

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HotSpot, the JVM we all know and love, is the brain in which our Java and Scala juices flow. Over the years, it’s been improved and tweaked by more than a handful of engineers, and with every iteration, the speed and efficiency of its code execution is nearing that of native compiled code. At its core lies the JIT (“Just-In-Time”) ...

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Monitoring and detecting memory leaks in your java application

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So your application is running out of memory, you’re spending days and nights analyzing your application hoping to catch the memory holes in your objects. The next steps will explain how to monitor and detect your memory leaks to make sure your app is on the safe side. 1. Memory leak suspicion If you have a suspicion there is a memory leak a convenient way to make sure ...

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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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