JEPs proposed to target JDK 9 (2015/5/21)

[Ben Evans]

Hi Mark,

I've mostly been very pleased with the JEPs targeted at JDK 9.
However, I have to object to:

248: Make G1 the Default Garbage Collector

My reasoning is as follows:

I have been working with G1 for ~5 years, ever since it was
experimental (& highly crash-prone in JDK 6).

In the intervening time, I have seen dozens (if not hundreds) of
installations, across a wide range of customers. I have participated
in, or been consulted on at least a dozen direct trials of GC
alternatives.

It is only in the last 18 months that I have seen *any* real-life
workload on G1 beat the alternatives, and only in the last 12 months
that I've had any customer prepared to go live with G1 in production.

>From my experience, I think that G1 is a fine collector, with a bright
future that should be pursued. However, I haven't seen anything that
would make a switch to it as default collector seem compelling in the
JDK 9 timeframe.

Obviously, my experience is not universal, so I'd like to ask you / Oracle:

1) Can you explain the survey methodology and customer testing that
you performed to arrive at the conclusion that G1 is ready to become
default?

2) Can you share aggregate results of the surveying ("We worked with X
customers and ran Y tests of G1 vs alternatives, and in Z% of cases,
G1 worked better by W margin")?

3) Can you ask some of the customers you worked with to speak publicly
about the trials you ran with them?

Thanks,

Ben


On Fri, May 22, 2015 at 7:05 AM,  <mark.reinhold at oracle.com> wrote:
> The following JEPs have been placed into the "Proposed to Target"
> state by their owners after discussion and review:
>
>   233: Generate Run-Time Compiler Tests Automatically
>        http://openjdk.java.net/jeps/233
>
>   246: Leverage CPU Instructions for GHASH and RSA
>        http://openjdk.java.net/jeps/246
>
>   248: Make G1 the Default Garbage Collector
>        http://openjdk.java.net/jeps/248
>
>   249: OCSP Stapling for TLS
>        http://openjdk.java.net/jeps/249
>
>   250: Store Interned Strings in CDS Archives
>        http://openjdk.java.net/jeps/250
>
>   252: Use CLDR Locale Data by Default
>        http://openjdk.java.net/jeps/252
>
> Feedback on these proposals is more than welcome, as are reasoned
> objections.  If no such objections are raised by 23:00 UTC next
> Thursday, 28 May, or if they're raised and then satisfactorily
> answered, then per the JEP 2.0 process proposal [1] I'll target
> these JEPs to JDK 9.
>
> (This information is also available on the JDK 9 Project Page [2]).
>
> - Mark
>
>
> [1] http://cr.openjdk.java.net/~mr/jep/jep-2.0-02.html
> [2] http://openjdk.java.net/projects/jdk9/