RFR (L): 8065972: Remove support for ParNew+SerialOld and DefNew+CMS

Stefan Karlsson stefan.karlsson at oracle.com
Thu Nov 27 14:03:14 UTC 2014


On 2014-11-27 15:01, Bengt Rutisson wrote:
>
> Hi Mikael,
>
> Thanks for the review!
>
> StefanK found some more code to delete. :)
>
> Here's an updated webrev:
> http://cr.openjdk.java.net/~brutisso/8065972/hotspot-webrev.02/
>
> And here's the diff compared to the last one:
> cr.openjdk.java.net/~brutisso/8065972/hotspot-webrev.01-02.diff/

Looks good. :)

StefanK

>
> Thanks,
> Bengt
>
>
> On 2014-11-27 14:56, Mikael Gerdin wrote:
>> Hi Bengt,
>>
>> On 2014-11-26 14:50, Bengt Rutisson wrote:
>>>
>>> Hi Stefan,
>>>
>>> Thanks for looking at this!
>>>
>>> On 2014-11-26 14:42, Stefan Karlsson wrote:
>>>> Hi Bengt,
>>>>
>>>> The changes looks good. There are a couple of follow-up cleanups that
>>>> can be done as separate changes, but I don't think they are blocking
>>>> this patch.
>>>
>>> Agreed. I filed two cleanup bugs based on Mikael's review.
>>>
>>>>
>>>> http://cr.openjdk.java.net/~brutisso/8065972/hotspot-webrev.00/test/gc/startup_warnings/TestParNewSerialOld.java.frames.html 
>>>>
>>>>
>>>>
>>>> I think the summary should be changed to:
>>>>
>>>>   28 * @summary Test that the unsupported ParNew+SerialOld combination
>>>> does not start
>>>
>>> Good catch.
>>>
>>> Here's an updated webrev that fixes the summary and also removes the
>>> code that Mikael found:
>>>
>>> http://cr.openjdk.java.net/~brutisso/8065972/hotspot-webrev.01/
>>
>> Excellent! 600+ deleted lines!
>>
>> Looks good.
>>
>> /Mikael
>>
>>>
>>> Only the changes compared to the last webrev:
>>>
>>> http://cr.openjdk.java.net/~brutisso/8065972/hotspot-webrev.00-01.diff/
>>>
>>> Thanks,
>>> Bengt
>>>
>>>>
>>>>
>>>> StefanK
>>>>
>>>> On 2014-11-26 13:09, Bengt Rutisson wrote:
>>>>>
>>>>> Hi everyone,
>>>>>
>>>>> Can I have a couple of reviews for this change to remove the support
>>>>> for ParNew+SerialOld and DefNew+CMS?
>>>>>
>>>>> This work is part of  JEP 214 (http://openjdk.java.net/jeps/214).
>>>>>
>>>>> The main change is in the hotspot repo:
>>>>> http://cr.openjdk.java.net/~brutisso/8065972/hotspot-webrev.00/
>>>>>
>>>>> I also removed the ParNew runs from the jprt configuration:
>>>>> http://cr.openjdk.java.net/~brutisso/8065972/root-webrev.00/
>>>>>
>>>>> JBS bug:
>>>>> https://bugs.openjdk.java.net/browse/JDK-8065972
>>>>>
>>>>> Some notes about the change:
>>>>>
>>>>> - UseParNewGC is now a redundant flag. It can only be used with CMS,
>>>>> so it will always have the same value as UseConcMarkSweepGC. Since
>>>>> UseParNewGC was not one of the flags that were deprecated in JDK 8,
>>>>> we decided to leave the flag in for JDK 9 but print a warning message
>>>>> that it is deprecated. We plan on removing UseParNewGC in JDK 10.
>>>>>
>>>>> Here's how the VM will behave with different values of UseParNewGC
>>>>> after my change:
>>>>>
>>>>> $ java -XX:+UseParNewGC -version
>>>>> It is not possible to combine the ParNew young collector with the
>>>>> Serial old collector.
>>>>> Error: Could not create the Java Virtual Machine.
>>>>> Error: A fatal exception has occurred. Program will exit.
>>>>>
>>>>> $ java -XX:-UseParNewGC -version
>>>>> Java HotSpot(TM) 64-Bit Server VM warning: The UseParNewGC flag is
>>>>> deprecated and will likely be removed in a future release
>>>>> java version "1.9.0-internal-debug"
>>>>> Java(TM) SE Runtime Environment (build
>>>>> 1.9.0-internal-debug-brutisso_2014_11_05_09_40-b00)
>>>>> Java HotSpot(TM) 64-Bit Server VM (build
>>>>> 1.9.0-internal-debug-brutisso_2014_11_05_09_40-b00, mixed mode)
>>>>>
>>>>> $ java -XX:+UseParNewGC -XX:+UseConcMarkSweepGC -version
>>>>> Java HotSpot(TM) 64-Bit Server VM warning: The UseParNewGC flag is
>>>>> deprecated and will likely be removed in a future release
>>>>> java version "1.9.0-internal-debug"
>>>>> Java(TM) SE Runtime Environment (build
>>>>> 1.9.0-internal-debug-brutisso_2014_11_05_09_40-b00)
>>>>> Java HotSpot(TM) 64-Bit Server VM (build
>>>>> 1.9.0-internal-debug-brutisso_2014_11_05_09_40-b00, mixed mode)
>>>>>
>>>>> $ java -XX:-UseParNewGC -XX:+UseConcMarkSweepGC -version
>>>>> It is not possible to combine the DefNew young collector with the CMS
>>>>> collector.
>>>>> Error: Could not create the Java Virtual Machine.
>>>>> Error: A fatal exception has occurred. Program will exit.
>>>>>
>>>>> - The NEW_C_HEAP_ARRAY and "new" calls in initialize_generations()
>>>>> methods will exit if they fail. No need to check for null after those
>>>>> calls. This simplified the two implementations significantly.
>>>>>
>>>>> - At a few places I've changed from "DefNewGeneration* dng =
>>>>> (DefNewGeneration*)_young_gen;" to "DefNewGeneration* dng =
>>>>> _young_gen->as_DefNewGeneration();". The as_DefNewGeneration() method
>>>>> does the asserts that were often placed before the original casting
>>>>> code.
>>>>>
>>>>> - In concurrentMarkSweepGeneration.cpp I left the casting to
>>>>> DefNewGeneration even though we could now use the more specific
>>>>> ParNewGeneration. I prefer to do such an update later (if at all)
>>>>> since that might come with its own complications regarding virtual
>>>>> calls etc.
>>>>>
>>>>> - The two methods must_be_youngest() and must_be_oldest() were
>>>>> unused. Removing them was not strictly needed for this change, but
>>>>> seemed like a nice thing to do anyway and I don't think it clutters
>>>>> the webrev much.
>>>>>
>>>>> - UseParNewGC is now always true when UseConcMarkSweepGC is true. And
>>>>> it is always false when UseConcMarkSweepGC is false. If statements
>>>>> that used to test against both flags have been simplified to only
>>>>> test against UseConcMarkSweepGC. This means that UseParNewGC is now
>>>>> only used in arguments.cpp
>>>>>
>>>>> - Similarly JTreg tests that used UseParNewGC have been changed to
>>>>> use UseConcMarkSweepGC instead. This should make it easy to remove in
>>>>> JDK 10.
>>>>>
>>>>> - The change to make/jprt.properties only affects the internal
>>>>> testing system we have. It will no longer test the ParNew+SerialOld
>>>>> combination (which is no longer supported). Note that DefNew+CMS was
>>>>> not tested at all by JPRT.
>>>>>
>>>>> Thanks,
>>>>> Bengt
>>>>
>>>
>



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