JEP 291: Deprecate the Concurrent Mark Sweep (CMS) Garbage Collector
Jeremy Manson
jeremymanson at google.com
Fri Nov 11 06:05:06 UTC 2016
Thanks, Erik. Jungwoo will take a look (he already responded to one).
Jeremy
On Wed, Nov 9, 2016 at 7:26 AM, Erik Helin <erik.helin at oracle.com> wrote:
> Hi Jeremy,
>
> Thanks for taking notes. I have created separate email threads on
> hotspot-gc-dev at openjdk.java.net for three enhancements to G1 that we
> think will make G1 be more like CMS for the use cases discussed during the
> meeting. The ideas are described in:
> - "RFC: Throughput barriers for G1"
>
> http://mail.openjdk.java.net/pipermail/hotspot-gc-dev/2016-N
> ovember/019215.html
> - "RFC: Parallel full collection for G1"
>
> http://mail.openjdk.java.net/pipermail/hotspot-gc-dev/2016-N
> ovember/019216.html
> - "RFC: Rebuilding remembered sets during concurrent mark"
>
> http://mail.openjdk.java.net/pipermail/hotspot-gc-dev/2016-N
> ovember/019217.html
>
> Please respond to these ideas in the respective email thread. We would be
> happy to help out with the design and integration if you and/or any
> external contributor would like too look into any (or all) of these ideas.
>
> Thanks,
> Erik
>
> On 10/21/2016 08:37 PM, Jeremy Manson wrote:
>
>> Hi folks,
>>
>> We had the face to face at JavaOne on 9/20. I took notes, which are
>> linked from the bug:
>>
>> https://bugs.openjdk.java.net/browse/JDK-8142518
>> <https://bugs.openjdk.java.net/browse/JDK-8142518>
>>
>> (Sorry about the delay - anything that happens at a quarterly boundary
>> takes me twice as long because of the Google planning cycle).
>>
>> The current plan for followup includes Erik Helin figuring out what
>> extracting CMS code from Hotspot will actually look like, and Paul Su
>> providing a list of ideas for helping G1 close the performance gap. See
>> meeting notes for more followup actions.
>>
>> We didn't specify a timeline for the next meeting. Paul (cc'd) said he
>> had to go do some due diligence about getting the list of ideas. It
>> would be great if he and / or Erik could talk about when a good time for
>> the next sync would be.
>>
>> Jeremy
>>
>> On Sat, Aug 27, 2016 at 5:42 PM, Jeremy Manson <jeremymanson at google.com
>> <mailto:jeremymanson at google.com>> wrote:
>>
>> Thanks, Jon.
>>
>> If we are going to do it, I'd (selfishly) like to see it done
>> earlier in the JDK 10 time frame, so that we can start contributing
>> our patches for it for JDK 10 earlier, rather than later. But JDK
>> 10 time frame is fine.
>>
>> Assuming you are asking me about management issues: I just
>> (Thursday) got back from the vacation I mentioned, so I've only just
>> spoken about it with our management. Naturally, no immediate
>> answer, but there's a lot of interest, and we plan to have more
>> conversations in the near term.
>>
>> For a variety of reasons (most of which I've already articulated), I
>> strongly believe we will have to do *something*, and it will mostly
>> be a question of whether this is the right path. Since we have
>> ~three years before the issue becomes immediate, that gives us a bit
>> of breathing room to do the right thing. Other possibilities
>> include spending the time until JDK 10 making G1 do what we need, or
>> figuring out another GC entirely (we'd want to evaluate, e.g.,
>> Shenandoah).
>>
>> (Since the G1 possibility is clearly of interest to you folks: We
>> would have to decide a) that it is technically feasible, and b) that
>> you folks were likely to take the patches. In addition to finding a
>> path forward to lowering the cost of the write barrier dramatically
>> and dealing with the memory footprint issues (not sure this is
>> possible), we would also have to reimplement, e.g., our parallel
>> Full GC patch, as well as a number of other changes we've made to
>> CMS locally.)
>>
>> I'd like what we end up doing to be something palatable to the
>> community, since CMS is obviously filling a very important role in
>> the ecosystem that won't get filled if it gets abandoned.
>>
>> Jeremy
>>
>> On Tue, Aug 23, 2016 at 9:23 PM, Jon Masamitsu
>> <jon.masamitsu at oracle.com <mailto:jon.masamitsu at oracle.com>> wrote:
>>
>> 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
>>> <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>
>>>>>>
>>>>>
>>>>>
>>>>>
>>>>
>>>>
>>>
>>>
>>>
>>>
>>
>>
>>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <https://mail.openjdk.org/pipermail/hotspot-gc-dev/attachments/20161110/50476bcc/attachment.htm>
More information about the hotspot-gc-dev
mailing list