if (rtn.isZero()) { Space.printUsageMB(); Assert.fail("Failed to allocate space for queue.  Is metadata virtual memory exhausted?"); }
  final Address alloc() throws InlinePragma {    Address rtn = rps.acquire(PAGES_PER_BUFFER);    if (Assert.VERIFY_ASSERTIONS) Assert._assert(rtn.EQ(bufferStart(rtn)));    return rtn;  }