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When using direct memory can be faster

Overview Using direct memory is no guarantee of improving performance.  Given it adds complexity, it should be avoided unless you have a compelling reason to use it. This excellent article by Sergio Oliveira Jr shows its not simply a matter of using direct memory to improve performance Which one is faster: Java heap or native memory? Where direct memory and memory mapped files ...

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Java Heap Dump: Are you up to the task?

If you are as much enthusiasm as I am on Java performance, heap dump analysis should not be a mystery to you. If it is then the good news is that you have an opportunity to increase your Java troubleshooting skills and JVM knowledge. The JVM has now evolve to a point that it is much easier today to generate ...

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IBM AIX: Java process size monitoring

This article will provide you with a quick reference guide on how to calculate the Java process size memory footprint for Java VM processes running on IBM AIX 5.3+ OS. This is a complementary post to my original article on this subject: how to monitor the Java native memory on AIX. I highly recommend this read to any individual involved ...

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Compact Off-Heap Structures/Tuples In Java

In my last post I detailed the implications of the access patterns your code takes to main memory. Since then I’ve had a lot of questions about what can be done in Java to enable more predictable memory layout. There are patterns that can be applied using array backed structures which I will discuss in another post. This post will ...

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JavaOne 2012: Diagnosing Your Application on the JVM

It was worth attending Staffan Larsen‘s (Oracle Java Serviceability Architect) presentation ‘Diagnosing Your Application on the JVM‘ (Hilton Plaza A/B) just for learning of the new jcmd command-line tool provided with Oracle’s JVM 7. The rest of the presentation was ‘bonus’ for me, which was nice for the last session I attended on Wednesday of JavaOne 2012. The Oracle HotSpot ...

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JavaOne 2012: Looking into the JVM Crystal Ball

I returned to Plaza A/B in the Hilton to attend the fourth session on Monday, but first went up to the top floor of the Hilton to pick up lunch. I’m reminded every year on the first day of JavaOne how surprisingly frustrating the first day’s lunch acquiring process is for everyone involved. I know I found the experience a ...

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VisualVM: Monitoring Remote JVM Over SSH (JMX Or Not)

java-interview-questions-answers

VisualVM is a great tool for monitoring JVM (5.0+) regarding memory usage, threads, GC, MBeans etc. Let’s see how to use it over SSH to monitor (or even profile, using its sampler) a remote JVM either with JMX or without it. This post is based on Sun JVM 1.6 running on Ubuntu 10 and VisualVM 1.3.3. 1. Communication: JStatD vs. ...

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