JEP 248: Make G1 the Default Garbage Collector

mark.reinhold at mark.reinhold at
Thu Jun 4 22:08:35 UTC 2015

2015/6/4 6:44 -0700, charlie.hunt at
> Wanted to come back to this thread, continue the dialog, reiterate the
> objective, (try to) summarize the concerns and put forth a potential
> plan for this JEP going forward.
> Intent: Use G1 GC as the default collector chosen by the JVM when no
> GC is explicitly set at the JVM command line.
> ...

Charlie -- thanks for the excellent summary of this wide-ranging

> ...
> Suggested plan for moving forward:
> - Make G1 the default collector in JDK 9, continue to evaluate G1 and
>   enhance G1 in JDK 9
> - Mitigate risk by reverting back to Parallel GC before JDK 9 goes
>   “Generally Available” (Sept 22, 2016 [1]) if warranted by continuing
>   to monitor observations and experiences with G1 in both JDK 9
>   pre-releases and latest JDK 8 update releases
> - Address enhancing ergonomics for selecting a default GC as a
>   separate JEP if future observations suggests its needed

I think this is a fine plan.

Stefan -- To move forward with JEP 248, could you please revise the
second item in the "Risks and Assumptions" section to note that there
is some concern that G1 might not be ready to become the default, that
making it the default now will allow us to get more feedback on it, and
that if it proves to be not ready then we'll revert the default to the
Parallel GC in time for JDK 9 GA?

Ben -- Can you live with this plan?

- Mark

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