fallback_env     2963 opal/mca/hwloc/hwloc201/hwloc/hwloc/topology-linux.c   char * fallback_env = getenv("HWLOC_KNL_HDH_FALLBACK");
fallback_env     2964 opal/mca/hwloc/hwloc201/hwloc/hwloc/topology-linux.c   int fallback = fallback_env ? atoi(fallback_env) : -1; /* by default, only fallback if needed */