RFR (XS): -8064865: Remove the debug funciontality RotateCMSCollectionTypes for CMS

[Jon Masamitsu]

On 11/13/2014 11:09 PM, Bengt Rutisson wrote:
>
> On 2014-11-14 08:05, Bengt Rutisson wrote:
>>
>> Hi all,
>>
>> Can I have a couple of reviews for this small change to remove a 
>> debug flag from CMS?
>>
>> http://cr.openjdk.java.net/~brutisso/8064865/webrev.00/
>
> I should have pointed out that this patch is based on top of the patch 
> for JDK-8064702 that is currently out for review.

Change looks good.   Reviewed.

Jon

>
> Bengt
>
>>
>> https://bugs.openjdk.java.net/browse/JDK-8064865
>>
>> Background:
>>
>> During the review of "8064702: Remove the CMS foreground collector" 
>> it was discussed how to handle the RotateCMSCollectionTypes feature. 
>> It was suggested to remove this feature in a separate change. This is 
>> the change to remove that feature.
>>
>> From the bug description:
>>
>> The RotateCMSCollectionTypes flag is used in CMS to rotate between 
>> the three different kinds of collections of the old generation that 
>> CMS has; background collection, foreground collection and full 
>> compacting serial GC.
>>
>> The functionality is only available in non-product builds.
>>
>> With JDK-8064702 the foreground collector is being removed. This 
>> means that there are only two types left. The 
>> RotateCMSCollectionTypes flag is not being automatically tested and 
>> it is very rarely used. Rather than maintaining it we should remove 
>> this functionality. If we need this for debugging in the future it is 
>> a pretty simple patch to add back. But for the most part it should be 
>> possible to debug in other ways, by for example using 
>> ExplicitGCInvokesConcurrent flag and similar.
>>
>> Thanks,
>> Bengt
>