Merge branches 'doc.2021.01.06a', 'fixes.2021.01.04b', 'kfree_rcu.2021.01.04a', ...

[sfrench/cifs-2.6.git] / Documentation / admin-guide / kernel-parameters.txt

diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index 18f3aa759e5424c266d4e0a8e6167edc051512d6..b1d6cd58a04c7979ccb14aa0b9fffa67b85ce6c3 100644 (file)
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -4092,6 +4092,10 @@
                        value, meaning that RCU_SOFTIRQ is used by default.
                        Specify rcutree.use_softirq=0 to use rcuc kthreads.
 
+                       But note that CONFIG_PREEMPT_RT=y kernels disable
+                       this kernel boot parameter, forcibly setting it
+                       to zero.
+
        rcutree.rcu_fanout_exact= [KNL]
                        Disable autobalancing of the rcu_node combining
                        tree.  This is used by rcutorture, and might
@@ -4179,12 +4183,6 @@
                        Set wakeup interval for idle CPUs that have
                        RCU callbacks (RCU_FAST_NO_HZ=y).
 
-       rcutree.rcu_idle_lazy_gp_delay= [KNL]
-                       Set wakeup interval for idle CPUs that have
-                       only "lazy" RCU callbacks (RCU_FAST_NO_HZ=y).
-                       Lazy RCU callbacks are those which RCU can
-                       prove do nothing more than free memory.
-
        rcutree.rcu_kick_kthreads= [KNL]
                        Cause the grace-period kthread to get an extra
                        wake_up() if it sleeps three times longer than
@@ -4338,6 +4336,14 @@
                        stress RCU, they don't participate in the actual
                        test, hence the "fake".
 
+       rcutorture.nocbs_nthreads= [KNL]
+                       Set number of RCU callback-offload togglers.
+                       Zero (the default) disables toggling.
+
+       rcutorture.nocbs_toggle= [KNL]
+                       Set the delay in milliseconds between successive
+                       callback-offload toggling attempts.
+
        rcutorture.nreaders= [KNL]
                        Set number of RCU readers.  The value -1 selects
                        N-1, where N is the number of CPUs.  A value
@@ -4470,6 +4476,13 @@
                        only normal grace-period primitives.  No effect
                        on CONFIG_TINY_RCU kernels.
 
+                       But note that CONFIG_PREEMPT_RT=y kernels enables
+                       this kernel boot parameter, forcibly setting
+                       it to the value one, that is, converting any
+                       post-boot attempt at an expedited RCU grace
+                       period to instead use normal non-expedited
+                       grace-period processing.
+
        rcupdate.rcu_task_ipi_delay= [KNL]
                        Set time in jiffies during which RCU tasks will
                        avoid sending IPIs, starting with the beginning