Advice on G1 garbage collector use for Confluence 5?

With Confluence 5 (and likely all other Atlassian products) requiring Java 7, are there any recommendations for or against using the relatively new G1 Garbage Collector that ships with Java 7? I'd like to move to using it since we're using about 6 GB of heap (one of the use cases that the link describes), but I'd appreciate input and if there are any data from tests that have been run before putting it into use. If you're wondering what JVM flag to specify, it's -XX:+UseG1GC

4 answers

1 accepted

Hi Jim,

I haven't had time to test the new G1 collector yet but I have high hopes that it will improve the throughput of GC in large Confluence instances, but it seems the most important feature is to be able to specify the pause time and the collector will try to keep to it. However, it is a new innovation so I would recommend testing it out before deploying it in production but it does appear like the CMS collector without the required tuning so it could well help when instances are struggling with GC issues.

All the best,

Hi John,

Thanks for the answer! It would be great to see a report comparing G1 to the default garbage collector similar to a report that was written a while back comparing Confluence to Clustered Confluence. I've tried to look for it recenly but can't find it. Although we don't use Clustered Confluence, maybe using G1 would help in situations that might otherwise need Clustered Confluence.



I keep a GC history on our large financial clustered instance. When I roll out 5.2 on 1.7 in the next month, I intend on testing G1, as GC is one of the things that plagues our instances. All nodes Full GC at once and.. yea.

Object creation in Confluence is off the hook. Add a lot of MS-Office users and the corresponding renders and it gets ugly fast. I have never seen a jprofiler report quite like it. I am glad they started rewriting parts of the office connector, some of the 3rd party libraries looked like CS Student projects (example: Jxcel).

0 vote

There's a feature request about this at

Hi Matt,

Thanks for the update!  This is great news to hear.




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