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

[Stefan Johansson]

Hi Ben,

Did you follow the discussion when the JEP was presented as a candidate 
[1]? That discussion shows both sides of the coin, some think changing 
the default is good, some don't. It's important to remember that we do 
not remove any of the other collectors and specifying -XX:+UseParallelGC 
will make the VM behave like before the change. For customers specifying 
a GC explicitly the change will have no effect, and the expectation is 
that most customers tuning for performance do this.

Thanks,
Stefan

[1] 
http://mail.openjdk.java.net/pipermail/hotspot-dev/2015-April/018322.html

On 2015-05-22 02:15, Ben Evans wrote:
> 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/