RFR (S): 8227089: Add timing information for merging humongous remembered sets

[Kim Barrett]

> On Jul 10, 2019, at 11:40 AM, Thomas Schatzl <thomas.schatzl at oracle.com> wrote:
> 
> Hi all,
> 
>  can I have reviews for this change that adds timing information for
> the part of the merge heap roots phase that dumps eager reclaim
> candidates onto the card table?
> 
> I am aware that the eager reclaim phase is actually single threaded -
> there is an extra CR for fixing this (JDK-8141637). At least with
> recent change that effort is hidden by the other work in this phase;
> but until now we did not know that there may be an issue.
> 
> CR:
> https://bugs.openjdk.java.net/browse/JDK-8227089
> Webrev:
> http://cr.openjdk.java.net/~tschatzl/8227089/webrev
> Testing:
> hs-tier1-5
> 
> Thanks,
>  Thomas

Looks good.