leaf rcu_node structure. Useful for very large
systems.
+ rcutree.jiffies_till_sched_qs= [KNL]
+ Set required age in jiffies for a
+ given grace period before RCU starts
+ soliciting quiescent-state help from
+ rcu_note_context_switch().
+
rcutree.jiffies_till_first_fqs= [KNL]
Set delay from grace-period initialization to
first attempt to force quiescent states.