Experiment: Merging hs-rt and hs-gc

Volker Simonis volker.simonis at gmail.com
Fri May 29 17:46:37 UTC 2015

+1 from a port maintainers perspective


On Fri, May 29, 2015 at 7:31 PM, Mikael Vidstedt
<mikael.vidstedt at oracle.com> wrote:
> All,
> As you all know the JDK 9 development of Hotspot is done in three different
> mercurial forests: hs-rt[1], hs-gc[2] and hs-comp[3]. This division has
> served as a way of isolating changes from each other in order to get more
> testing done on them before they are shared to other forests. However, as a
> side effect of this the propagation time of fixes is also impacted, and in
> some cases we have seen fixes stuck for several weeks waiting for the
> respective forests to stabilize.
> We would like to propose an experiment, which will merge the hs-rt and hs-gc
> forests, having hs-rt be the forest through which all the hs-rt and hs-gc
> changes are integrated. For the duration of the experiment the hs-gc forest
> will be locked down so that no accidental integrations are made to it. This
> change would mean that the combined hs-rt gets more testing faster, and that
> the fix propagation time goes to zero for changes between hs-rt and hs-gc.
> The hs-comp forest will not be affected.
> We suggest that the experiment starts June 4th and goes on for at least two
> weeks (giving us some time to adapt in case of issues). Monitoring and
> evaluation of the new structure will take place continuously, with an option
> to revert back if things do not work out. This will remain an experiment for
> at least a few months, after which we will evaluate it and depending on the
> results consider making it the new standard. If so, the hs-gc forest will
> eventually be retired, with an option of looking at further reduction of
> forests going forward.
> It's worth pointing out explicitly that if you have any changes based on the
> hs-gc forest those changes would have to be rebased on top of hs-rt instead
> once the hs-gc forest has been locked down.
> Please let us know if you have any feedback or questions!
> Cheers,
> Mikael
> [1] http://hg.openjdk.java.net/jdk9/hs-rt
> [2] http://hg.openjdk.java.net/jdk9/hs-gc
> [3] http://hg.openjdk.java.net/jdk9/hs-comp

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