[8u] Shenandoah SA: Support live region iteration

[Roman Kennke]

Hi Zhengyu,

Could this go to an appropriate Jira-ID as backport? E.g.:

https://bugs.openjdk.java.net/browse/JDK-8220602

Or is this not related?

Also, what about sh/jdk11, does it already support region iteration?

Other than that, the patch itself looks good, thanks!

Roman

> Please review this patch to support live region iteration, which should
> fix jstack with "-F" option.
> 
> However, with -F option, jstack takes *really* long time, but G1 has the
> same issue.
> 
> 
> Webrev:
> http://cr.openjdk.java.net/~zgu/shenandoah/sa_liveregion/webrev.00/index.html
> 
> 
> Thanks,
> 
> -Zhengyu
>