RFR (L): 8064702: Remove the CMS foreground collector

[Bengt Rutisson]

Hi Kim,

On 2014-11-13 22:28, Kim Barrett wrote:
> On Nov 13, 2014, at 11:11 AM, Kim Barrett <kim.barrett at oracle.com> wrote:
>> On Nov 13, 2014, at 2:23 AM, Bengt Rutisson <bengt.rutisson at oracle.com> wrote:
>>>> ------------------------------------------------------------------------------
>>>>
>>>> src/share/vm/gc_implementation/concurrentMarkSweep/concurrentMarkSweepGeneration.cpp
>>>>
>>>> 1254     if (RotateCMSCollectionTypes &&
>>>> 1255         (_cmsGen->debug_collection_type() !=
>>>> 1256           ConcurrentMarkSweepGeneration::Concurrent_collection_type)) {
>>>> 1257       assert(_cmsGen->debug_collection_type() !=
>>>> 1258         ConcurrentMarkSweepGeneration::Unknown_collection_type,
>>>> 1259         "Bad cms collection type");
>>>> 1260       return false;
>>>> 1261     }
>>>>
>>>> =>
>>>>
>>>> 1252     if (RotateCMSCollectionTypes) {
>>>> 1253       return _cmsGen->debug_concurrent_cycle();
>>>> 1254     }
>>>>
>>>> I spent a large amount of time studying this change, because there are
>>>> behavioral changes here that looked suspicious.  I think I've decided
>>>> it's ok, but RotateCMSCollectionTypes is now badly named, and was
>>>> never well described and had (and still has) unclear semantics.  I
>>>> think I've puzzled out more or less what it means, but that required
>>>> reading a lot of code, and I'm still not confident that I know what
>>>> would happen if I used it, or why I might want to.
>>> Right. I agree that it is unclear if this code is needed. I have never been running with RotateCMSCollectionTypes but I did not want to remove it as part of this change.
>>>
>>> […]
>>>
>>> I do agree that the naming is bad. But if we decide to remove this functionality there is not much need to spend time on the naming discussion.
>> My inclination would be to remove it. […]
> Just to be clear, I’m ok with deferring removal to a later task.  Please file a bug report…

Great, thanks!

I filed a bug (JDK-8064865) and sent out a review request.

Thanks again for looking at this and thanks for the review!
Bengt


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