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

Jon Masamitsu jon.masamitsu at oracle.com
Wed Aug 24 04:23:26 UTC 2016


All,

I've been working on the examples and we're been discussing (arguing)
about them here.  They are failing into at least the following
classes

- Use inheritance to specialize for CMS (specialize card table is
envisioned as an example).
- Use a GC Interface to request something different for CMS (different write
barriers for example).
- Compile code under macros
     Similar to INCLUDE_ALL_GCS
     Leaves calls to specialized CMS code visible in the shared code
     Involves some code refactoring
- Move more code to the cms directory (ParNew for example)
- Custom solutions which might use one or more of the above techniques.
- Argument processing I don't know about yet.

We're still arguing about the example so they're not here.

As I've said Oracle would not drop support of CMS until at least
jdk 10 so working on separating out the code would be work
for the jdk 10 time frame.   Do people have reasons to get that
done earlier rather than later?

Also is your management's support for spending engineering time
on this effort a slam-dunk?   Or a qualified maybe?   I'm trying to
get a feel for how real this CMS project is.

Jon


On 8/1/2016 1:49 PM, Jeremy Manson wrote:
> For those following along at home, the meeting happened last week.  We 
> took notes, which are linked from the bug:
>
> https://bugs.openjdk.java.net/browse/JDK-8142518
>
> The current plan for followup is to set up a meeting for the end of 
> August, and then a f2f during JavaOne.
>
> Jeremy
>
> On Thu, Jul 21, 2016 at 9:46 AM, Jeremy Manson 
> <jeremymanson at google.com <mailto:jeremymanson at google.com>> wrote:
>
>     I was drafting an agenda.  My expectation is that the meeting will
>     go something like this:
>
>     Introductions
>
>     Discussion of motivations for JEP 291 (Jon M)
>
>     Discussions of concerns about JEP 291 (roundtable)
>
>     Discussion / Brainstorming about potential ways forward, as well
>     as an understanding of what level of commitment organizations are
>     willing to make.
>
>     Discussion of action items and followup.
>
>     Jeremy
>
>
>     On Thu, Jul 21, 2016 at 7:39 AM, Martijn Verburg
>     <martijnverburg at gmail.com <mailto:martijnverburg at gmail.com>> wrote:
>
>         Hi Jon,
>
>         For me it's to see if there are enough folks who are willing
>         *and* capable (to be blunt, it will need the backing of large
>         companies) of maintaining CMS as a collector going forwards
>         (it's important to several of our customers).  If that's a yes
>         then I'd hope to have a technical discussion around the
>         options of how we could achieve that without causing a major
>         headache for the Oracle GC engineers.
>
>
>         Cheers,
>         Martijn
>
>         On 20 July 2016 at 23:50, Jon Masamitsu
>         <jon.masamitsu at oracle.com <mailto:jon.masamitsu at oracle.com>>
>         wrote:
>
>             What are peoples expectations for this meeting?
>
>             Jon
>
>             On 07/18/2016 10:16 AM, Jeremy Manson wrote:
>>             Presumably, everyone will be happy with meeting notes
>>             rather than an actual recording.
>>
>>             Otherwise, I'll add:
>>
>>             ysr1729 at gmail.com <mailto:ysr1729 at gmail.com>
>>             mark.reinhold at oracle.com <mailto:mark.reinhold at oracle.com>
>>
>>
>>
>>             On Mon, Jul 18, 2016 at 8:13 AM,
>>             kirk.pepperdine at gmail.com
>>             <mailto:kirk.pepperdine at gmail.com>
>>             <kirk.pepperdine at gmail.com
>>             <mailto:kirk.pepperdine at gmail.com>> wrote:
>>
>>                 ok we can record if everyone is open to that.
>>
>>>                 On Jul 18, 2016, at 7:48 AM, Jeremy Manson
>>>                 <jeremymanson at google.com
>>>                 <mailto:jeremymanson at google.com>> wrote:
>>>
>>>                 Richard - I'll bring someone who can take readable
>>>                 notes. :)
>>>
>>>                 Jeremy
>>>
>>>                 On Sat, Jul 16, 2016 at 5:07 AM,
>>>                 kirk.pepperdine at gmail.com
>>>                 <mailto:kirk.pepperdine at gmail.com>
>>>                 <kirk.pepperdine at gmail.com
>>>                 <mailto:kirk.pepperdine at gmail.com>> wrote:
>>>
>>>                     Hi Richard,
>>>
>>>                     I think it’s in everyone’s interest to keep this
>>>                     out in the open.
>>>
>>>                     Kind regards,
>>>                     Kirk
>>>
>>>>                     On Jul 16, 2016, at 1:34 AM, Richard Warburton
>>>>                     <richard.warburton at gmail.com
>>>>                     <mailto:richard.warburton at gmail.com>> wrote:
>>>>
>>>>                     Hi,
>>>>
>>>>                         Sounds as if the consensus is a telephone /
>>>>                         video conference in the near term, and then
>>>>                         a F2F during / close to JavaOne.
>>>>
>>>>                         People who want to be invited include:
>>>>
>>>>                         kirk at kodewerk.com <mailto:kirk at kodewerk.com>
>>>>                         aph at redhat.com <mailto:aph at redhat.com>
>>>>                         volker.simonis at gmail.com
>>>>                         <mailto:volker.simonis at gmail.com>
>>>>                         jon.masamitsu at oracle.com
>>>>                         <mailto:jon.masamitsu at oracle.com>
>>>>                         jeremymanson at google.com
>>>>                         <mailto:jeremymanson at google.com>
>>>>                         martijnverburg at gmail.com
>>>>                         <mailto:martijnverburg at gmail.com>
>>>>                         jwha at google.com <mailto:jwha at google.com>
>>>>
>>>>                         Did I miss anyone? We can take date / time
>>>>                         planning and logistics off-list.
>>>>
>>>>
>>>>                     Given that this change affects a lot of
>>>>                     organisations and people in the wider Java
>>>>                     community I think it would be really
>>>>                     appreciated that a brief summary of the
>>>>                     discussion be published somewhere in public.
>>>>                     Maybe this mailing list?
>>>>
>>>>                     regards,
>>>>
>>>>                       Richard Warburton
>>>>
>>>>                     http://insightfullogic.com
>>>>                     @RichardWarburto
>>>>                     <http://twitter.com/richardwarburto>
>>>
>>>
>>
>>
>
>
>
>

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