RFR: 8227226: Segmented array clearing for ZGC

[Erik Österlund]

Hi Ryan,

This looks good in general. Just some stylistic things...

1) In the ZGC project we like the letter 'Z' so much that we put it in 
front of everything we possibly can, including all class names.
2) We also explicitly state things are private even though it's 
bleedingly obvious.

So:

39 class PinAllocating {
40 HeapWord* _mem;
41 public: -> 39 class ZPinAllocating { 40 private:    41 HeapWord* _mem;
   42
  41 public: I can be your sponsor and push this change for you. I don't 
think there is a need for another webrev for my small stylistic remarks, 
so I can just fix that before pushing this for you. On that note, I'll 
add me and StefanK to the contributed-by section as we all worked out 
the right solution to this problem collaboratively. I have run through 
mach5 tier1-5, and found no issues with this patch. Thanks, /Erik

On 2019-07-05 17:18, Sciampacone, Ryan wrote:
> http://cr.openjdk.java.net/~phh/8227226/webrev.00/
> https://bugs.openjdk.java.net/browse/JDK-8227226
>
> This patch introduces safe point checks into array clearing during allocation for ZGC.  The patch isolates the changes to ZGC as (in particular with the more modern collectors) the approach to incrementalizing or respecting safe point checks is going to be different.
>
> The approach is to keep the region holding the array in the allocating state (pin logic) while updating the color to the array after checks.
>
> Can I get a review?  Thanks.
>
> Ryan