[the8472]

There are plans for adding one to hotspot[1]. As I understand it it can't use the same tricks as C4 because that would require kernel support, but unlike CMS it will be compacting, thus avoiding the terrible failure modes of CMS.

There also is some work being done to make the CMS failures a little less terrible by parallelizing them.[2]

[1] http://openjdk.java.net/jeps/189 [2] https://bugs.openjdk.java.net/browse/JDK-8086706

[pron]

As HotSpot's GC team is mostly working on G1 and grooming it as a CMS replacement (it has replaced the parallel GC as the default GC in current JDK9 builds), I don't think there's much further work on CMS.

[the8472]

The CMS improvements I've mentioned to are being contributed by a 3rd party. Based on the mailing list posts[1] I think it was google.

[1] http://mail.openjdk.java.net/pipermail/hotspot-gc-dev/2015-J...

[pron]

That's really cool! I hope it gets merged...