RFR [S][2/7] 8197570: Make rules for choosing collection set candidates more explicit

[sangheon.kim]

Hi Thomas,

On 03/05/2018 06:22 AM, Thomas Schatzl wrote:
> Hi all,
>
>    can I have reviews for this change that makes the rule (occupancy)
> for choosing collection set candidates more explicit, i.e. factor it
> into a single method. This is needed for selecting the regions we want
> to rebuild the remembered sets concurrently (JDK-8180415) more
> straightforward.
>
> It also adds a method to allow iteration over the regions in the
> collection set - I did not see that worth an extra webrev.
>
> CR:
> https://bugs.openjdk.java.net/browse/JDK-8197570
> Webrev:
> http://cr.openjdk.java.net/~tschatzl/8197570/webrev/
Looks good.

One minor nit:
You can add 'const' qualifier to the newly added method, 
CollectionSetChooser::should_add(HeapRegion* hr).

I don't need a new webrev for this.

Thanks,
Sangheon


> Testing:
> hs-tier 1-5, mostly in conjunction with related changes
>
> Thanks,
>    Thomas
>