RFR: 8196217: NMT: add_committed_regions doesn't merge succeeding regions

[coleen.phillimore at oracle.com]

This change looks good.
Coleen

On 1/26/18 4:37 AM, Stefan Karlsson wrote:
> Hi all,
>
> Please review this patch to fix merging of committed regions in NMT. 
> Before this patch, only the regions without 'next' regions were merged.
>
> http://cr.openjdk.java.net/~stefank/8196217/webrev.01/
>
> This was found while running stress tests on ZGC:
> http://mail.openjdk.java.net/pipermail/zgc-dev/2018-January/000127.html
>
> Tested with the new test in the patch and the rest of the tests in 
> test/hotspot/jtreg/runtime/NMT.
>
> Thanks,
> StefanK