Duration of Excessive GC Time in “java.lang.OutOfMemoryError: GC overhead limit exceeded”

Question

Occasionally, somewhere between once every 2 days to once every 2 weeks, my application crashes in a seemingly random location in the code with: java.lang.OutOfMemoryE

Answer 1

I'm trying to determine a best approach to actually solving this issue rather than just using -XX:-UseGCOverheadLimit but I feel a need to better understand the issue I'm solving.

Well, you're using too much memory - and from the sound of it, it's probably because of a slow memory leak.

You can try increasing the heap size with -Xmx, which would help if this isn't a memory leak but a sign that your app actually needs a lot of heap and the setting you currently have is slightly to low. If it is a memory leak, this'll just postpone the inevitable.

To investigate if it is a memory leak, instruct the VM to dump heap on OOM using the -XX:+HeapDumpOnOutOfMemoryError switch, and then analyze the heap dump to see if there are more objects of some kind than there should be. http://blogs.oracle.com/alanb/entry/heap_dumps_are_back_with is a pretty good place to start.

---

Edit: As fate would have it, I happened to run into this problem myself just a day after this question was asked, in a batch-style app. This was not caused by a memory leak, and increasing heap size didn't help, either. What I did was actually to decrease heap size (from 1GB to 256MB) to make full GCs faster (though somewhat more frequent). YMMV, but it's worth a shot.

Edit 2: Not all problems solved by smaller heap... next step was enabling the G1 garbage collector which seems to do a better job than CMS.