RFR (L): JDK-8061308: Remove iCMS

Mikael Gerdin mikael.gerdin at oracle.com
Wed Oct 22 12:46:54 UTC 2014


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)

Otherwise the change looks good to me.

>
> 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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