RCU_FANOUT_1
#define RCU_FANOUT_2 (RCU_FANOUT_1 * RCU_FANOUT)
#if NR_CPUS <= RCU_FANOUT_1
# define NUM_RCU_LVL_1 DIV_ROUND_UP(NR_CPUS, RCU_FANOUT_1)
# define NUM_RCU_LVL_2 DIV_ROUND_UP(NR_CPUS, RCU_FANOUT_1)
# define NUM_RCU_LVL_3 DIV_ROUND_UP(NR_CPUS, RCU_FANOUT_1)