RFR (L): JDK-8061308: Remove iCMS

Bengt Rutisson bengt.rutisson at oracle.com
Thu Oct 23 07:59:22 UTC 2014


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/

>
> 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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