What's That Noise?! [Ian Kallen's Weblog]

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20060201 Wednesday February 01, 2006

Large Heap Sizes and OOM

Note to self: If you're getting OutOfMemoryError's, bumping up the heap size may actually make the problem worse. Usually, OOM means you've exceeded the JVM's capacity... so you set -Xms and -Xmx to a higher strata of memory allocation. Well, at least I thought that was the conventional wisdom. Having cranked it up to 1850M to open very large data structures, OOM's were still bringing down the house. OK, spread the work around in smaller chunks across multiple JVMs. But it still bombs out. It turns out that you have to be very particular about giving the JVM a lot of heap up front. This set of posts seems to peg it. I'd figured that nailing a big heap allocation was how I'd prevent OOM'ing. Looks like it's time for me to bone up on JVM tuning. I should probably dig into 64-bit Java while I'm at it.

( Feb 01 2006, 11:57:15 PM PST ) Permalink