Future of CMS

Jon Masamitsu jon.masamitsu at oracle.com
Sat Jun 11 15:48:01 UTC 2016

Hi Ramki,

I added the hotspot-gc-dev mailing list to the CC.  It should have been
there all the time.

On 6/10/2016 6:43 PM, Ramki Ramakrishna wrote:
> Hi Jon --
> How are you? Thanks for the heads-up; we really appreciate it!
> I suspect the right thing to do in that case is to split the CMS code 
> off into its own subdirectory (which is to a certain degree already 
> the case), and to allow the possibility of building it or not based on 
> a build time option or make target.
> That way the OpenJDK community can continue to use it while Oracle can 
> stop worrying about it.

I think that would fit our needs.

> May be we can discuss this within our respective teams and then we can 
> meet to discuss the details of how to make this work?

It would be nice to get a list of companies that would like to be involved.
Maybe an Openjdk project.  Eventually with its own mailing list.

> I haven't been monitoring the gc/openjdk aliases. If this is being 
> discussed there (and that would be the right place so any othe teams 
> interested in CMS can have a voice), we'll make sure to join that 
> discussion.

As I said above, I meant to have the hotspot-gc-dev on the CC.

> thanks, and have a good weekend!
> -- ramki
> On Fri, Jun 10, 2016 at 6:17 PM, Jon Masamitsu 
> <jon.masamitsu at oracle.com <mailto:jon.masamitsu at oracle.com>> wrote:
>     Jungwoo, Ramki, Tony (and other friends of CMS),
>     I wanted to be sure you guys saw this JEP.
>     Deprecate the CMS garbage collector (UseConcMarkSweepGC).
>     http://openjdk.java.net/jeps/8142518
>     I know you do development on CMS and wanted to know if
>     had thoughts about the future of CMS.
>     At some point Oracle is going to stop supporting CMS.
>     The burden of testing and maintaining the CMS code doesn't
>     make much sense given that we think G1 is the better
>     collector.    If we deprecate CMS in jdk9, support would be dropped
>     no earlier than jdk10.
>     Have you guys talked about what you would like to do with regard
>     to continuing CMS development without Oracle's help?
>     I've been told that if CMS exists in the Oracle binaries, then
>     customers will expect it to work.  So not supporting CMS
>     means it is not in the build.
>     Jon

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