JEP 291: Deprecate the Concurrent Mark Sweep (CMS) Garbage Collector

[Roman Kennke]

> 2017/4/5 1:29:28 -0700, aph at redhat.com:
>> On 05/04/17 08:45, Roman Kennke wrote:
>>> I'd say it's too early to talk about removing CMS. And, to be honest, I
>>> even question the move to deprecate it. What's going to happen if
>>> somebody actually takes over CMS maintainership? Un-deprecate it?
>> Indeed.  We need to think about this first.  I expect that there
>> will be someone interested enough to keep it going.
> Since this JEP was posted last summer we've had several discussions
> aimed at identifying a new maintainer for CMS, on the hotspot-gc-dev
> list [1][2] and in open meetings whose minutes are attached to the
> JEP issue [3].
>
> So far, no one has stepped up.
>
> If someone does step up soon then I expect the owner of this JEP will
> withdraw it.  If someone does so later on then CMS can be un-deprecated
> at that time.  In any case, Oracle does intend to stop maintaining CMS
> at some point in the not-to-distant future, and if no one ever steps up
> then we'll remove the code.

Ok, I'll bite. I've heard a lot of people saying that they're interested
in keeping it alive, but no-one stepped up yet. I can say that I
wouldn't step up personally and take all of it. But I'd certainly
participate in such an effort. (In a sense I'm already doing it by
working on the GC interface). So why not pull our resources together and
do it as a shared/community effort? Then it probably doesn't take that
much from every single person/entity involved?

From the top off my head, here's some items that would need to be done:
1. continuous build with CMS turned on (assuming it can be disabled by a
build-time switch)
2. fix occasional build failure (caused by changes in, e.g., the GC
interfaces or other runtime stuff)
3. run tests with CMS
4 triage bug reports
5 fix bugs

I have certainly missed some aspects? Please feel free to add them!

CMS is a pretty mature code base, so I'd expect most work in 1 and 3
(which should be mostly automated after initial set-up), and 2 (which
shouldn't be very hard). 4 is also not very difficult. If something
comes up in 5, it's probably very hard.

I'm not afraid to touch GC code, so I'd be willing to participate in
anything code related (e.g. 2 and 5).

Oracle: you folks probably have CMS specific tests that are not in
OpenJDK yet? If so, would you be willing to contribute those?

Everybody (I've seen Google, jClarity, Twitter, SAP and a bunch of
individuals involved in discussions): who else would be willing to
contribute? And in which way?

Best regards, Roman