jemalloc_Run.java

class Run {
  Bin bin; // bins are further down in our discussion
  RegionSize regionSize; // the region size for this run.
  List<Page> pages; // pages that are a part of this run. 
  int numFreeRegions;
  int totalNumRegions = pages.size() / regionSize;
  boolean freeRegions[totalNumRegions]; // initially all set to true
  // more metadata to quickly identify the first available region
}