RFR: 8252513: ZGC: Contiguous memory reservation probing is broken for TB heap sizes

[Stefan Karlsson]

Hi all,

Please review this patch to fix memory reservation probing for large 
heap size.

https://cr.openjdk.java.net/~stefank/8252513/webrev.01/
https://bugs.openjdk.java.net/browse/JDK-8252513

If the passed in 'size' is equal to ZAddressOffsetMax, both 'end' and 
'increment' becomes 0, and the code will loop forever.

I've changed the code to at least increment with ZGranuleSize. I've also 
replaced the usage of 'start <= end', with 'start + size <= 
ZAddressOfsetMax', since it  makes the code easier to reason about, IMHO.

Thanks,
StefanK