RFR (L): JDK-8061308: Remove iCMS

Bengt Rutisson bengt.rutisson at oracle.com
Wed Oct 22 12:20:17 UTC 2014


Jon,

Thanks for looking at this!

On 2014-10-21 19:42, Jon Masamitsu wrote:
>
> On 10/17/14 4:43 AM, 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/
>
> Bengt,
>
> Looks good.  In fact, looks beautiful.

Thanks! :)

>
> There are a couple of comments in the
> concurrentMarkSweepGeneration.* files than
> mention EdenSpace that you might want to
> clean up.
>
> 5566   // a set of parallel tasks (via the sampling that the [abortable]
> 5567   // preclean phase did of EdenSpace, plus the [two] tasks of
> 5568   // scanning the [two] survivor spaces. Further fine-grain
>
> 5188       if (chunk_top == 0) {  // no samples were taken
> 5189         assert(nth_task == 0 && n_tasks == 1, "Can have only 1 
> EdenSpace ta     sk");
> 5190         start = space->bottom();

Good catch. I am not sure what I should change to though. I think 
EdenSpace was, in these two contexts, more a reference to eden than to a 
space. How about I change both occurrences to just "eden"?

Bengt

>
> Reviewed.
>
>>
>> JDK changes:
>> http://cr.openjdk.java.net/~brutisso/8061308/jdk/
>> (Just a small update to a test library class.)
>
> Looks good.
>
> Reviewed.
>
> Jon
>>
>> 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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