RFR: 8218746: SA: Implement discontiguous bitmap for ZGC

[Jini George]

Hi Stefan,

Looks good to me. Nit: Could you please modify the copyright year? And 
don't we have to add the copyright message to the new file 
ZExternalBitMap.java ?

Thanks!
Jini.

On 2/11/2019 7:25 PM, Stefan Karlsson wrote:
> Hi all,
> 
> Please review this patch to implement a discontiuous bitmap for ZGC in 
> the SA.
> 
> http://cr.openjdk.java.net/~stefank/8218746/webrev.01/
> https://bugs.openjdk.java.net/browse/JDK-8218746
> 
> ZGC uses a 16TB virtual memory address range, so the normal scheme to 
> map a bitmap over the entire address range uses too much memory. This 
> patch lazily creates smaller bitmaps per ZPage, when at() or atPut() is 
> called.
> 
> This patch builds upon JDK-8218743.
> 
> Tested with serviceability/sa and manually running Reverse Object 
> Analysis in the SA.
> 
> Thanks,
> StefanK