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It has to be noted that on HotSpot the object header is only two words not three words like on J9. Basically Flags and Locks fit into one word on HotSpot whereas they use two words on J9.

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Only on 32 bit IIRC, headers are 12 byte on 64 bit with CompressedOops (the default for heaps <32gb) and 16 bytes without. The bit layout of the markoop is here:

http://hg.openjdk.java.net/jdk8/jdk8/hotspot/file/87ee5ee275...

You are correct.

J9 has had one-word headers for years now. I think this article was already out of date in 2012 when it was published.

That sounds interesting. Do you have source that you can share?

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