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Tag Archives: JVM

Java Debugger – The Definitive List of Tools

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Java debugging is a complex space. There are many types of debuggers, and numerous tools to choose from. In this page, we’ll cover the differences between 7 types of debuggers, and review the major tools in each category to help you choose the right tool for the right job. Here are the types of debuggers we cover:       ...

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(Part 1 of 3): Synopsis of articles & videos on Performance tuning, JVM, GC in Java, Mechanical Sympathy, et al

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I have been contemplating for a number of months about reviewing a cache of articles and videos on topics like Performance tuning, JVM, GC in Java, Mechanical Sympathy, etc… and finally took the time to do it – may be this was the point in my intellectual progress when was I required to do such a thing! Thanks to Attila-Mihaly for giving ...

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G1 vs CMS vs Parallel GC

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This post is following up the experiment we ran exactly a year ago comparing the performance of different GC algorithms in real-life settings. We took the same experiment, expanded the tests to contain the G1 garbage collector and ran the tests on different platform. This year our tests were run with the following Garbage Collectors: -XX:+UseParallelOldGC -XX:+UseConcMarkSweepGC -XX:+UseG1GC Description of ...

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Investigating Memory Leaks Part 1 – Writing Leaky Code

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I found this little problem the other day: there’s this server that runs for a while and then falls over. It’s then restarted by its startup script and the whole process repeats itself. This doesn’t sound that bad as it isn’t business critical although there is a significant loss of data, so I decided to take a closer look and ...

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Crashing your JVM

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Thorough testing can be harmful as we discovered recently. Extending our test coverage led us to a several-hours debugging session caused by just one line of code. What made the debugging particularly unpleasant was the fact that the code crashed not just the JVM it was deployed to, but also the virtual and/or physical machine underneath. So, run the following ...

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Java VM – Beware of the YoungGen space

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As you may have seen from our previous performance oriented articles, a healthy JVM is one of the most important goals to achieve for optimal application performance and stability. Such health assessment is very often only focusing on the frequency (avoidance) of major collections or detecting the presence of memory leaks. What about the sizing and footprint of the Young ...

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What Garbage Collector are you using?

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Our research labs are humming at full speed. With the recent injection of capital, we can only warrant that the pace at which we keep innovating will only increase. Part of the research we conduct is related to GC optimizations. While dealing with the problems in this interesting domain, we thought to share some insights to GC algorithm usage. For ...

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Java final fields on x86 a no-op?

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I have always enjoyed digging in to the details of multi-threaded programming, and always enjoy that despite reading for years about CPU memory consistency models, wait-free and lock-free algorithms, the java memory model, java concurrency in practice, etc. etc. — I still create multi-threaded programming bugs. It’s always a wonderfully humbling experience that reminds me how complicated of a problem ...

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Running out of memory without the OutOfMemoryError

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This is actually a reincarnation of a post originally posted in ~2010. The flashback occurred when listening to our engineers cursing at a particularly nasty bug raising its head yesterday. When the cursing stopped, I stepped by to verify my doubts. Lo and behold, I was correct – the mood swing was caused by an app running out of the ...

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Add Some Entropy to Your JVM

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Being able to generate true random numbers depends on the entropy in your system. Some claim, that this can be guaranteed by fair dice roll. Others think that replacing the OpenJDK’s java.math.Random.nextInt() method with this body will help:                 public int nextInt() { return 14; } Source: http://www.redcode.nl/blog/2013/10/openjdk-and-xkcd-random-number/. But that’s absurd. We all know ...

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