Home » Tag Archives: JVM (page 7)

Tag Archives: JVM

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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How To Write Your Own Java / Scala Debugger

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With this post we’ll explore how Java / Scala debuggers are written and work. Native debuggers such WinDbg for Windows or gdb for Linux/Unix get their power from hooks provided to them directly by the OS to monitor and manipulate the state of an external process. The JVM, acting as an abstraction layer on top of the OS, provides its ...

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Java Mission Control 5.2 is Finally Here! Welcome 7u40!

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It has been a while since we last heard of this fancy little thing called Mission Control. It came all the way from JRockit and was renamed to Java Mission Control. This is one of the parts which literally survived the convergence strategy between HotSpot and JRockit. With today’s Java SE 7 Update 40 you can actually use it again. ...

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Dealing With Slow Resource Leaks

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Finding resource leaks using Java-monitor Finding slow resource leaks is key to keeping your application servers up and running for very long times. Here I explain how I use Java-monitor to spot slow resource leaks and how to verify that they are actual leaks and not just extra pre-allocation into some HTTP connector or database pool. If you follow these ...

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Understanding the OutOfMemoryError

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Whenever you find yourself staring a stacktrace with OutOfMemoryError in it, it should all be crystal clear. The program has got no more elbow room and is dying just because of lack of it. From the 10,000 feet or executive chair this might already contain too much information. But those of you who have to build or maintain the applications ...

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