share/gc/g1/g1PageBasedVirtualSpace.cpp

rev 1 : G1GC+POGC+NVDIMM Patch with latest comments incorporated from all.
rev 2 : Removed fcntl and fixed hotspot else violation

*** 132,141 ****
--- 132,155 ----
             start, start + num_pages, _committed.size());
  
    char* start_addr = page_start(start);
    size_t size = num_pages * _page_size;
  
+   if (((address)start_addr == (address)os::nvdimm_heapbase())) {
+     // first remove my dummy mapping.
+     if (os::unmap_memory(start_addr, size)) {
+         char* nvdimm_addr = os::attempt_reserve_memory_at(size, start_addr, os::nvdimm_fd());
+         if (nvdimm_addr != start_addr)  {
+           vm_exit_during_initialization(
+             err_msg("Could not map memory at %p for NVDIMM %s Fd %d", nvdimm_addr, AllocateOldGenAt, os::nvdimm_fd()));
+         } else {
+           log_info(gc, heap)("NVDIMM Memory successfully mapped at %p, Size %lu", start_addr, size);
+           os::close(os::nvdimm_fd());
+         }
+     }
+     return;
+   }
    os::commit_memory_or_exit(start_addr, size, _page_size, _executable,
                              err_msg("Failed to commit area from " PTR_FORMAT " to " PTR_FORMAT " of length " SIZE_FORMAT ".",
                              p2i(start_addr), p2i(start_addr + size), size));
  }