JEP 291: Deprecate the Concurrent Mark Sweep (CMS) Garbage Collector
Erik Helin
erik.helin at oracle.com
Wed Nov 16 15:59:44 UTC 2016
On 11/11/2016 07:05 AM, Jeremy Manson wrote:
> Thanks, Erik. Jungwoo will take a look (he already responded to one).
Thanks, appreciate it. Do you have any idea at the moment when we can
expect some results from the experiments?
Thanks,
Erik
> Jeremy
>
> On Wed, Nov 9, 2016 at 7:26 AM, Erik Helin <erik.helin at oracle.com
> <mailto: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
> <mailto: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-November/019215.html
> <http://mail.openjdk.java.net/pipermail/hotspot-gc-dev/2016-November/019215.html>
> - "RFC: Parallel full collection for G1"
>
> http://mail.openjdk.java.net/pipermail/hotspot-gc-dev/2016-November/019216.html
> <http://mail.openjdk.java.net/pipermail/hotspot-gc-dev/2016-November/019216.html>
> - "RFC: Rebuilding remembered sets during concurrent mark"
>
> http://mail.openjdk.java.net/pipermail/hotspot-gc-dev/2016-November/019217.html
> <http://mail.openjdk.java.net/pipermail/hotspot-gc-dev/2016-November/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>
> <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>
> <mailto: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>
> <mailto: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>
> <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>
> <mailto: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>
> <mailto: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>
> <mailto: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> <mailto:ysr1729 at gmail.com
> <mailto:ysr1729 at gmail.com>>
> mark.reinhold at oracle.com
> <mailto:mark.reinhold at oracle.com>
> <mailto: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>
> <mailto:kirk.pepperdine at gmail.com
> <mailto:kirk.pepperdine at gmail.com>>
> <kirk.pepperdine at gmail.com
> <mailto:kirk.pepperdine at gmail.com>
> <mailto: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>
>
> <mailto: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>
>
> <mailto:kirk.pepperdine at gmail.com
> <mailto:kirk.pepperdine at gmail.com>>
> <kirk.pepperdine at gmail.com
> <mailto:kirk.pepperdine at gmail.com>
>
> <mailto: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>
>
> <mailto: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>
>
> <mailto:kirk at kodewerk.com
> <mailto:kirk at kodewerk.com>>
> aph at redhat.com
> <mailto:aph at redhat.com> <mailto:aph at redhat.com
> <mailto:aph at redhat.com>>
>
> volker.simonis at gmail.com
> <mailto:volker.simonis at gmail.com>
>
> <mailto:volker.simonis at gmail.com
> <mailto:volker.simonis at gmail.com>>
>
> jon.masamitsu at oracle.com
> <mailto:jon.masamitsu at oracle.com>
>
> <mailto:jon.masamitsu at oracle.com
> <mailto:jon.masamitsu at oracle.com>>
>
> jeremymanson at google.com
> <mailto:jeremymanson at google.com>
>
> <mailto:jeremymanson at google.com
> <mailto:jeremymanson at google.com>>
>
> martijnverburg at gmail.com
> <mailto:martijnverburg at gmail.com>
>
> <mailto:martijnverburg at gmail.com
> <mailto:martijnverburg at gmail.com>>
> jwha at google.com
> <mailto:jwha at google.com>
>
> <mailto: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
> <http://twitter.com/richardwarburto>>
>
>
>
>
>
>
>
>
>
>
>
>
>
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