RFR (L): JDK-8061308: Remove iCMS

Jon Masamitsu jon.masamitsu at oracle.com
Tue Oct 21 17:42:17 UTC 2014


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.

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();

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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