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

[Bengt Rutisson]

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.

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