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G1 segfaults reliably

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ryanobjc
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Joined: 2009-12-03
Points: 0

I am a developer on an open source database project, and we are interested in the G1 GC (one of the most interesting improvements in java7)... but the problem is, I can reliably get the JVM to crash when using G1! Over the last 6 months of java7 snapshots I've tested, it's improved, but it's pretty distressing to see segfault in libjvm.so.

I've attempted to file bugs, but the repro case is hard. It is definitely G1 in nature, because normally we dont segfault the JVM and it only happens when the G1GC is turned on. The variant shipped with java6 is pretty horrid, to the point of crashing within minutes.

There seems to be surprisingly little buzz over the G1 - it seems like the cure to our CMS woes. Anyone even interested in this GC?

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ijuma
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Joined: 2005-10-19
Points: 0

Hi,

There is definitely quite a bit of interest in G1, but I think it's common knowledge that it's not ready for production yet. The fact that -XX:+UnlockExperimentalVMOptions is required to use it in JDK6 makes that quite clear. JDK6u18 should have a much improved version, but if the JDK7 version doesn't work for you, then that is unlikely to work either.

Reporting bugs is definitely useful, particularly crashes. For difficult to reproduce bugs, it may be possible to use debug switches to narrow it down. You may want to post in the OpenJDK GC mailing list to ask more information about that.

Best,
Ismael