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

Mikael Gerdin mikael.gerdin at oracle.com
Thu Nov 27 13:56:56 UTC 2014


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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