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

Wessam Hassanein wessam at google.com
Wed Jan 31 01:37:45 UTC 2018

Thanks Paul, we will definitely take both G1 JDK9 & JDK10 improvements in
our analysis. We would appreciate you updating the thread when a final
decision is made for CMS in JDK11.

On Tue, Jan 30, 2018 at 5:15 PM, Jeremy Manson <jeremymanson at google.com>

> Thanks, Paul.  We're definitely going to re-evaluate G1 with a more modern
> JDK, but to do it for real, we need to re-evaluate it alongside something
> that can run CMS in a production setting.  Getting a JDK and our codebase
> to the point where that is possible at Google is quite a bit of work, so it
> would be a lot of work for us to rush to do it for 9 or 10 and then start
> again for 10/11.
> (The work for 9/10 would help us for 11, but there would be quite a bit of
> extra work, as well.)
> In short: "unlikely" is definitely good news for us.  :)  We'll watch this
> space for updates, in case that changes.
> Jeremy
> On Tue, Jan 30, 2018 at 4:07 PM, Paul Su <paul.su at oracle.com> wrote:
>> 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> <jeremymanson at google.com>
>> To: Wessam Hassanein <wessam at google.com> <wessam at google.com>
>> CC: hotspot-gc-dev at openjdk.java.net openjdk.java.net
>> <hotspot-gc-dev at openjdk.java.net> <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>
>> wrote:
>>> Hi All,
>>> Per JEP 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) 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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