[PATCH tip/core/rcu 07/10] rcu: Fix RCU_FANOUT help message

[Paul E. McKenney]

Commit cf244dc01bf68 added a fourth level to the TREE_RCU hierarchy,
but the RCU_FANOUT help message still said "cube root".  This commit
fixes this to "fourth root" and also emphasizes that production
systems are well-served by the default.  (Stress-testing RCU itself
uses small RCU_FANOUT values in order to test large-system code paths
on small(er) systems.)

Located-by: John Kacur <jkacur@xxxxxxxxxx>
Signed-off-by: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx>
---
 init/Kconfig |    9 ++++++---
 1 files changed, 6 insertions(+), 3 deletions(-)

diff --git a/init/Kconfig b/init/Kconfig
index 9366954..7faa5d8 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -384,9 +384,12 @@ config RCU_FANOUT
 	help
 	  This option controls the fanout of hierarchical implementations
 	  of RCU, allowing RCU to work efficiently on machines with
-	  large numbers of CPUs.  This value must be at least the cube
-	  root of NR_CPUS, which allows NR_CPUS up to 32,768 for 32-bit
-	  systems and up to 262,144 for 64-bit systems.
+	  large numbers of CPUs.  This value must be at least the fourth
+	  root of NR_CPUS, which allows NR_CPUS to be insanely large.
+	  The default value of RCU_FANOUT should be used for production
+	  systems, but if you are stress-testing the RCU implementation
+	  itself, small RCU_FANOUT values allow you to test large-system
+	  code paths on small(er) systems.
 
 	  Select a specific number if testing RCU itself.
 	  Take the default if unsure.
-- 
1.7.0.6

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