RFR (L): 8219100: Improve do_collection_pause_at_safepoint

[sangheon.kim at oracle.com]

Hi Thomas,

On 3/4/19 3:16 AM, Thomas Schatzl wrote:
> Hi all,
>
>    can I have reviews for this (relatively big) cleanup change that
> reorganizes the G1CollectedHeap::do_collection_pause_at_safepoint()
> method to be (imho) much more readable?
>
> - refactored out some methods, mainly verification but also other
> helpers
> - grouped together "same" category calls so that e.g. collection set
> related methods are not more or less randomly interspersed with
> unrelated code
> - moved code into the right "levels" of indentation
> - moved code related to evacuation that kind of bleeded out of
> pre/post_evacuate_collection_set() into it, also trying to improve
> grouping and ordering
>
> CR:
> https://bugs.openjdk.java.net/browse/JDK-8219100
> Webrev:
> http://cr.openjdk.java.net/~tschatzl/8219100/webrev
Nice cleanup!

One minor nit:  the changed method name of 
G1ConcurrentMark::verify_no_collection_set_oops_in_stacks() seems 
questionable.
Removing '_in_stacks' or updating its comment(as it says stacks and 
fingers) looks better but it's your call.
I'm okay as is too.

Thanks,
Sangheon


> Testing:
> hs-tier1-8
>
> Thanks,
>    Thomas
>