Potential optimization to the GC termination protocol in JDK8

[Thomas Schatzl]

Hi,

On Fri, 2018-06-08 at 11:54 -0500, T S wrote:
> On Fri, Jun 8, 2018 at 2:35 AM Thomas Schatzl <thomas.schatzl at oracle.
> com> wrote:
> > 
> > Hi,
> > 
> >   sorry for being somewhat late in that thread... busy lately...
> > 
> > On Thu, 2018-04-26 at 08:53 +0200, Roman Kennke wrote:
> > > > > [Problem]
> > > > The work stealing during the GC takes lots of time to
> > > > terminate.
> > > > > 
[...]
> > Sure we are interested in such an enhancement and would appreciate
> > a contribution. However new work should be conducted in the latest
> > version only, i.e. at this time JDK 11 (and probably JDK 12 by the
> > time such a change would be pushed given the FC date of end of
> > June).
> > 
> 
> Hi Thomas,
> 
> Could you please send me a link for the JDK 11 or 12? I cannot find
> an official link on the openjdk website.
> 
> http://hg.openjdk.java.net/shenandoah/jdk/
> Is it the latest JDK under developed?

The always latest development happens in http://hg.openjdk.java.net/jdk
/jdk . From this, at regular intervals, we branch off to make releases.

The next branch will be jdk11, forked off around end of June, that's
why we are talking about "we are working on jdk11" (and jdk11-ea
releases are being made from jdk/jdk already all the time). As soon as
the fork happened, everything that gets into jdk/jdk will get into
jdk12.

http://hg.openjdk.java.net/shenandoah/jdk/ is a fork of jdk/jdk done at
some point, and kept up to date by maintainers. We typically do such
parallel development for larger features only, like in this case the
Shenandoah GC.
When all changes from shenandoah/jdk are merged (when the feature is
"done"), that branch may be closed for further development and all
Shenandoah-related development happens in jdk/jdk.
People are of course free to continue working in shenandoah/jdk :)

About your questions: the task terminator/stealing code did not change
for a looooong time. Most likely, apart from path changes of the files,
it applies cleanly.

Please, if you intend to contribute, make sure that step 0 on the "How
to contribute" [1] page has been done. Otherwise we (at Oracle at
least) are not allowed to look at your changes due to legal reasons.
This process typically takes a week or so.

Otherwise, when you are eager to contribute and want others to look at
your patches, the first thing that happens is that everyone needs to
wait instead of work...

Thanks,
  Thomas

[1] http://openjdk.java.net/contribute/