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-rw-r--r--init/Kconfig10
1 files changed, 8 insertions, 2 deletions
diff --git a/init/Kconfig b/init/Kconfig
index 558cc3638ab9..4119a44e4157 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -641,11 +641,17 @@ config RCU_FANOUT_LEAF
initialization. These systems tend to run CPU-bound, and thus
are not helped by synchronized interrupts, and thus tend to
skew them, which reduces lock contention enough that large
- leaf-level fanouts work well.
+ leaf-level fanouts work well. That said, setting leaf-level
+ fanout to a large number will likely cause problematic
+ lock contention on the leaf-level rcu_node structures unless
+ you boot with the skew_tick kernel parameter.
Select a specific number if testing RCU itself.
- Select the maximum permissible value for large systems.
+ Select the maximum permissible value for large systems, but
+ please understand that you may also need to set the skew_tick
+ kernel boot parameter to avoid contention on the rcu_node
+ structure's locks.
Take the default if unsure.