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authorPaul E. McKenney <paulmck@linux.vnet.ibm.com>2010-08-04 17:31:12 -0700
committerPaul E. McKenney <paulmck@linux.vnet.ibm.com>2010-08-19 17:18:04 -0700
commit4d87ffadbba88105f33271bef5f2c79366c6a4e1 (patch)
treeb9866241327c17a810c3c9ca9bac0f525762cb7e /init
parent910b1b7e19a292ff685001caf1bf1a9775b771a1 (diff)
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rcu: Fix RCU_FANOUT help message
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@redhat.com> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Diffstat (limited to 'init')
-rw-r--r--init/Kconfig9
1 files changed, 6 insertions, 3 deletions
diff --git a/init/Kconfig b/init/Kconfig
index 79ac52bef4c..dbc08baad77 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -388,9 +388,12 @@ 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.