+ * Multiple threads may want to read upcalls simultaneously from a single
+ * datapath. To support multiple threads well, one extends the above preferred
+ * behavior:
+ *
+ * - Each port has multiple PIDs. The datapath distributes "miss" upcalls
+ * across the PIDs, ensuring that a given flow is mapped in a stable way
+ * to a single PID.
+ *
+ * - For "action" upcalls, the thread can specify its own Netlink PID or
+ * other threads' Netlink PID of the same port for offloading purpose
+ * (e.g. in a "round robin" manner).
+ *