JDK6 GC Release notes

Here's a couple of pointers to the GC section of the release notes for JDK6.

Parallel Compaction

Concurrent Mark Sweep Collector Enhancements

Edit done May 16, 2007.

Ryan and Tobais, sorry but I just saw your comments. I could not figure out how to reply with a comment (comment period being closed and I didn't want to mess with the settings too much) so I'm editting the blog to respond.

Ryan,

The line "CMS-concurrent-abortable-preclean" does not indicate a problem. The "abortable" only indicates that the current phase (precleaning) can be interrupted in order to start the next phase.

Tobais,

Yes, the UseParallelOldGC does imply UseParallelGC.

Comments:

Trying the new CMS in 1.6 and it seems to work nicely for a while but then it starts kicking out these CMS aborts. I can find nothing anywhere talking about what is happening. This happens over and over until a full GC happens. From what I can tell the CMS collector never completes and is therefore not doing anything except taking CPU time. CMS: abort preclean due to time 407.606: [CMS-concurrent-abortable-preclean: 0.149/5.058 secs]

Posted by Ryan Krueger on February 13, 2007 at 01:09 AM PST #

Thanks! Could you please clarify if -XX:+UseParallelOldGC still needs a additional switch to enable the parallel GC of Eden or is that option implicit?

Posted by Tobias on February 15, 2007 at 12:39 AM PST #

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