RFR(S): Ensure collection set and cset map are consistent, and a few cleanup

[Zhengyu Gu]

Webrev updated: 
http://cr.openjdk.java.net/~zgu/shenandoah/cset_cleanup/webrev.01/index.html

Thanks,

-Zhengyu

On 05/31/2017 02:27 PM, Aleksey Shipilev wrote:
> On 05/31/2017 08:25 PM, Zhengyu Gu wrote:
>>>  *) Is removal of this branch meaningful? It was supposed to avoid some stores:
>>>
>>>  228         if (!r->is_root()) {
>>>  229           r->set_root(true);
>>>  230         }
>>
>> Just a bit awkward. Do those stores matter? It is at a safepoint, and you have
>> region in cache anyway.
>
> Yes it does. Trading write for branch is a profitable microoptimization,
> especially if you are looking into doing Threshold*NumRegions of writes ;)
>
> -Aleksey
>
>