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One Java program makes all java programs very slow  RSS feed

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Linux Mac OS X VI Editor
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I'm running Snow Leopard on my quad core MBP. I am developing Java programs on it. I have the Sun Java JDK.

java version "1.6.0_26"
Java(TM) SE Runtime Environment (build 1.6.0_26-b03-384-10M3425)
Java HotSpot(TM) 64-Bit Server VM (build 20.1-b02-384, mixed mode)

I'm seeing something on this OSX machine that I've never seen before. When I run a big, slow program, say one that processes a million big records, it can take a long time, several hours to run.

I find that while it is running, every other application that uses Java is also dog slow. Things like Vuze become so unresponsive as to be unusable.

It feels as if there is only one JVM on the box.

Top does not show more than one core being used heavily, and typically no Java process uses more than 50% of one core. Which makes sense, because the programs do a bit of java, then talk to MySql, then do a bit more, iterating back and forth.

Is this normal?
Is my guess (one JVM for the whole machine) likely? or correct?

Is there a way to run two JVMs at once? Its not as if there is anything in common between the code I write and the code in Vuze.
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