RCU_FANOUT_3
#define RCU_FANOUT_4 (RCU_FANOUT_3 * RCU_FANOUT)
#elif NR_CPUS <= RCU_FANOUT_3
# define NUM_RCU_LVL_1 DIV_ROUND_UP(NR_CPUS, RCU_FANOUT_3)