doc: Document the rcutree.rcu_divisor kernel boot parameter
This commit adds kernel-parameters.txt documentation for the
rcutree.rcu_divisor kernel boot parameter, which controls the softirq
callback-invocation batch limit.
Cc: Eric Dumazet <edumazet@google.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index 789ef58..b80c458 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -4584,6 +4584,21 @@
When RCU_NOCB_CPU is set, also adjust the
priority of NOCB callback kthreads.
+ rcutree.rcu_divisor= [KNL]
+ Set the shift-right count to use to compute
+ the callback-invocation batch limit bl from
+ the number of callbacks queued on this CPU.
+ The result will be bounded below by the value of
+ the rcutree.blimit kernel parameter. Every bl
+ callbacks, the softirq handler will exit in
+ order to allow the CPU to do other work.
+
+ Please note that this callback-invocation batch
+ limit applies only to non-offloaded callback
+ invocation. Offloaded callbacks are instead
+ invoked in the context of an rcuoc kthread, which
+ scheduler will preempt as it does any other task.
+
rcutree.rcu_nocb_gp_stride= [KNL]
Set the number of NOCB callback kthreads in
each group, which defaults to the square root
