RFR (L): JDK-8061308: Remove iCMS

Mikael Gerdin mikael.gerdin at oracle.com
Thu Oct 23 08:25:50 UTC 2014


Bengt,

On 2014-10-23 09:59, Bengt Rutisson wrote:
>
> Hi Mikael,
>
> Thanks for looking at this!
>
> On 2014-10-22 14:46, Mikael Gerdin wrote:
>> Hi Bengt,
>>
>> On 2014-10-17 13:43, Bengt Rutisson wrote:
>>>
>>> Hi everyone,
>>>
>>> Can I have a couple of reviews for this change?
>>>
>>> HotSpot changes:
>>> http://cr.openjdk.java.net/~brutisso/8061308/hotspot/
>>
>> The following can also be removed:
>>
>> src/share/vm/gc_implementation/concurrentMarkSweep/concurrentMarkSweepGeneration.cpp:
>>
>>
>> CMSStats::_cms_duration_per_mb (only used by
>> icms_update_duty_cycle_impl and CMSStats::print_on)
>>
>> 1040:static inline size_t percent_of_space(Space* space, HeapWord* addr)
>> (only used by allocation_limit_reached and icms_update_allocation_limits)
>>
>> src/share/vm/gc_implementation/concurrentMarkSweep/concurrentMarkSweepThread.hpp:
>>
>>
>> ConcurrentMarkSweepThread::trace_state(const char* desc)
>> (only used by icms_wait, {start,stop}_icms)
>> and its enabling flag CMSTraceThreadState (it's a develop flag)
>
> Great that you found this!
>
> Here's an updated webrev with your changes and the EdenSpace -> eden
> changes that Jon found:
>
> http://cr.openjdk.java.net/~brutisso/8061308/hotspot.01/
>
> Here's the diff compared to the last webrev:
>
> http://cr.openjdk.java.net/~brutisso/8061308/hotspot.00-01-diff/

Looks good.

/Mikael

>
>>
>> Otherwise the change looks good to me.
>
> Thanks!
>
> Bengt
>
>>
>>>
>>> JDK changes:
>>> http://cr.openjdk.java.net/~brutisso/8061308/jdk/
>>> (Just a small update to a test library class.)
>>
>> Looks good.
>>
>> /Mikael
>>
>>>
>>> JBS bug:
>>> https://bugs.openjdk.java.net/browse/JDK-8061308
>>>
>>> The change removes the incremental mode of CMS. This work is part of JEP
>>> 214 (http://openjdk.java.net/jeps/214). There are quite a few lines
>>> changed. Mostly it is just removal of code and it should hopefully be
>>> fairly straight forward to review.
>>>
>>> One interesting side effect of removing iCMS was that the ConcEdenSpace
>>> (a subclass in the Space hierarchy) could be removed. It implemented the
>>> "soft-end" feature that only iCMS was taking advantage of. When I had
>>> removed ConcEdenSpace it turned out that its superclass, EdenSpace, was
>>> actually an unnecessary class that did not add anything so I removed
>>> that too. When I then went to update the comment in space.hpp that
>>> describes the Space hierarchy I noticed that the description of the
>>> hierarchy was completely out-dated. Rather than bringing it up-to-date I
>>> removed the comment. I think that type of information will only get
>>> out-dated quickly again and it is much easier to let your IDE create the
>>> correct type hierarchy view dynamically for you.
>>>
>>> Thanks,
>>> Bengt
>


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