RFR(S) 8206467: Refactor G1ParallelCleaningTask into shared

[Roman Kennke]

Hi Zhengyu,

the change looks mostly good to me.

- There's a fwd decl lurking:

 139 class ParallelCleaningTask;

that you may want to move up right below the includes.

- Fix the copyright header in parallelCleaning.hpp

Thanks for doing this!
Roman

> Ping!
> 
> Thanks,
> 
> -Zhengyu
> 
> On 07/06/2018 12:56 PM, Zhengyu Gu wrote:
>> Hi,
>>
>> Shenandoah has a similar version that was derived from
>> G1ParallelCleaningTask, with additional time tracking of each cleaning
>> task.
>>
>> Due to code movement and renaming, the changeset appears to be large,
>> but it is really not. Other than the renaming, followings are the
>> actual diffs vs. current G1ParallelCleaningTask:
>>
>> - G1StringDedupUnlinkOrOopsDoClosure is passed as a parameter.
>>
>> - Counters (_string_processed, _string_removed, and etc.) in
>> StringAndSymbolCleaningTask are volatile now, cause they are updated
>> using atomic operations.
>>
>> - Added ParallelCleaningTimes and ParallelCleaningTaskTimer classes
>> for tracking times.
>>
>> - ParallelCleaningTask::work() added time tracking code.
>>
>>
>> Bug: https://bugs.openjdk.java.net/browse/JDK-8206467
>> Webrev: http://cr.openjdk.java.net/~zgu/8206467/webrev.00/
>>
>>
>> Test:
>>    hotspot_gc on Linux 64 (fastdebug and release)
>>
>>
>> Thanks,
>>
>> -Zhengyu
>>
>>
>>