Expected JDK version of when CMS code is suppose to be dropped, is it JDK11?

Paul Su paul.su at oracle.com
Wed Jan 31 00:07:54 UTC 2018


Hi Jeremy, Wessam,

  At this time, removal of CMS is still under consideration for JDK 11 but unlikely to happen within that timeframe. However, there were significant performance improvements to G1 in JDK 9 and 10, so it may be worthwhile to evaluate those with your use cases. As always, any feedback is welcome and appreciated. 

Thanks,
Paul

> 
> Subject:	Re: Expected JDK version of when CMS code is suppose to be dropped, is it JDK11?
> Date:	Tue, 30 Jan 2018 10:25:27 -0800
> From:	Jeremy Manson <jeremymanson at google.com> <mailto:jeremymanson at google.com>
> To:	Wessam Hassanein <wessam at google.com> <mailto:wessam at google.com>
> CC:	hotspot-gc-dev at openjdk.java.net <mailto:hotspot-gc-dev at openjdk.java.net> openjdk.java.net <hotspot-gc-dev at openjdk.java.net> <mailto:hotspot-gc-dev at openjdk.java.net>
> 
> Hi folks,
> 
> Wessam's question is pretty important to our planning.
> 
> As many of you know, we were unable to get the G1 collector as it shipped with JDK 8 to work well with our services.  We want to try a newer branch.
> 
> However, it also takes us a lot of work to make a JDK workable for internal use.  We have to patch it to work with our systems, and we have to make a whole lot of tests and infrastructure functional.
> 
> We'd rather not rush to get out a Java version that will stop being supported in a few months.  Java 9 has already seen its last release, and we aren't really all that close to making it work for the kinds of systems that actually care about the GC they are using.  We are debating whether to try to continue to make Java 9 work, move to Java 10, or to skip both and go with Java 11, which will see long term support.
> 
> (If we went to 11, we'd continue to experiment with 9 and 10, but we wouldn't push it hard.)
> 
> In order to switch to G1, we need a release where our services can compare a recent G1 with CMS.  If the last release with both of them is Java 10, then we need to work on Java 10, in spite of its September expiration date.  If the last release with both of them is Java 11, then we will have a lot more breathing room for the G1 migration, and we can target that instead.
> 
> So, it would be really helpful if someone could chime in with more information about the timeline for CMS removal.  Is it likely to be before the door closes for the Java 11 release?
> 
> Thanks!
> 
> Jeremy
> 
> On Fri, Jan 26, 2018 at 12:36 PM, Wessam Hassanein <wessam at google.com <mailto:wessam at google.com>> wrote:
> Hi All,
> 
> Per JEP 291( http://openjdk.java.net/jeps/291 <http://openjdk.java.net/jeps/291>) the CMS collector was deprecated but there was no clear date of when it is expected for the CMS code to be dropped. I see code refactoring in JDK10 JEP 304 (http://openjdk.java.net/jeps/304 <http://openjdk.java.net/jeps/304>) and I am wondering whether CMS is planned to be dropped in JDK11 or when it is expected to be dropped?
> 
> Thanks,
> 
> Wessam Hassanein
> Google GC TL
> 
> 

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