JEP 248: Make G1 the Default Garbage Collector

Ben Evans ben at
Tue Jun 2 12:22:15 UTC 2015

Of, course, but the point of the debate is that hasn't been proved yet.

By the way, I've kicked off a survey, initially to the LJC (but
opening it out now) about which GC people use.

With ~70 responses in, ~40% of people are using the default collector,
and ~10% don't know. Of those who do know & explicitly set, CMS is the
winner, with ~25%

I'll report back when we have more data.



On Mon, Jun 1, 2015 at 7:25 PM, charlie hunt <charlie.hunt at> wrote:
>> On Jun 1, 2015, at 12:54 PM, Ben Evans <ben at> wrote:
>>>>> One question that may be worth pondering … suppose G1 happened to be the default GC today, and there was a JEP to make Parallel GC the default GC. What would your reaction to that JEP be?  I’m asking that question since I’d like to get a sense if your concerns are more about conservatism (not wanting to change behavior), stability of G1 or otherwise.
>>>> Primarily conservatism. Of course, if G1 had been default, the
>>>> "unknown unknowns" would have been resolved by now, so there would be
>>>> no need to worry.
>>>> I think that if G1 was default, and the platform was as successful
>>>> across the same range of workloads as it is today, I'd be advocating
>>>> for no change.
>>> Is that because you think G1 would offer a better out of the box experience than Parallel GC, or because you would not want to see a change made to the JVM’s default GC?
>> I would not want to see a change made to the default behaviour that
>> could potentially negatively affect a large number of apps and in
>> doing so harm the long-term perception of the platform as a "safe pair
>> of hands”.
> And you also realize there could be a certain number (maybe as many as, or more) applications that could realize a better out of the box experience with G1 as the default versus Parallel GC being the default?  Implying of course that the “safe pair of hands” would have a better experience.
> thanks,
> charlie
>> Thanks,
>> Ben
>> --
>> Ben Evans, Co-founder jClarity @jclarity

Ben Evans, Co-founder jClarity @jclarity

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