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Jinwoo Hwang

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Top Stories by Jinwoo Hwang

We can visualize resource starvation using an elaborate rendition of the Dining Philosophers Problem. This classic metaphor of resource allocation among processes was first introduced in 1971 by Edsger Dijkstra in his paper "Hierarchical Ordering of Sequential Processes." It's been a model and universal method for verifying theories on resource allocation ever since. The metaphor goes like this: There are three well-known philosophers in an Asian bistro. Dinner is served but they are only given three chopsticks because the restaurant's supply truck has been stuck in a snow storm for a couple of days. Naturally each philosopher needs two chopsticks to eat his dinner and each is protected from interference while he uses a chopstick. Plato skipped lunch that day and insists that he should have priority or else he'll faint. If he doesn't give up his chopsticks, the other ... (more)

Unveiling the java.lang.Out OfMemoryError

When we encounter a java.lang.OutOfMemoryError, we often find that Java heap dumps, along with other artifacts, are generated by the Java Virtual Machine. If you feel like jumping right into a Java heap dump when you get a java.lang.OutOfMemoryError, don't worry, it's a normal thought. You may be able to discover something serendipitously, but it's not always the best idea to analyze Java heap dumps, depending on the situation you are facing. We first need to investigate the root cause of the java.lang.OutOfMemoryError. Only after the root cause is identified can we decide whether... (more)

Anatomy of a Java Finalizer

A couple of patterns that could cause Java heap exhaustion were identified from years of research at IBM. One interesting scenario was observed when Java applications generated an excessive amount of finalizable objects whose classes had non-trivial Java finalizers. What Is a Java Finalizer? A Java finalizer performs finalization tasks for an object. It's the opposite of a Java constructor, which creates and initializes an instance of a Java class. A Java finalizer can be used to perform postmortem cleanup tasks on an instance of a class or to release system resources such as file... (more)