RFR(M): 8204908: NVDIMM for POGC and G1GC - ReserveSpace.cpp changes are mostly eliminated/no collector specific code.

[Thomas Schatzl]

Hi Vinay,

On Thu, 2018-06-14 at 20:49 +0000, Awasthi, Vinay K wrote:
> Now ReservedSpace.cpp has logic to only open NVDIMM File (as it was
> done for AllocateheapAt).. if successful, set up 3 flags
> (base/nvdimm_present/file handle) at the end. There is *NO* collector
> specific code.
>  
> All work has been moved to g1PagebasedVirtualSpace.cpp.. I am
> committing memory here and setting dram_heapbase used by g1 here.
>  
> JEP to support allocating Old generation on NV-DIMM - https://bugs.op
> enjdk.java.net/browse/JDK-8202286
> Here is the implementation bug link: https://bugs.openjdk.java.net/br
> owse/JDK-8204908
>  
> 
> Patch is Uploaded at (full patch/incremental patch)
> 
> http://cr.openjdk.java.net/~kkharbas/8204908/webrev.02/
> http://cr.openjdk.java.net/~kkharbas/8204908/webrev.02_to_01/
> Tested default setup (i.e. no file is being passed for heap) and
> AllocateHeapAt/AllocateOldGenAt with POGC and G1GC.. all passing…
> Any and all comments are welcome!
> 

  looking briefly through the changes, I think they look much better
already to move the G1 specific stuff into G1 code; however I would
like to think about how we could reduce the complexity further and
solve the case of allowing multiple mapping sources (tmpfs file, nvram,
different "types" of RAM) for different parts of the heap in an even
cleaner way.

Thanks,
  Thomas