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authorPaul E. McKenney <paulmck@linux.vnet.ibm.com>2015-07-31 08:28:35 -0700
committerPaul E. McKenney <paulmck@linux.vnet.ibm.com>2015-10-06 11:09:41 -0700
commitee968ac61d5a3440b931375d81113e0eedfcb249 (patch)
treeac6f4bc6727b19506941412b6d09c5fe44ca8b3d /Documentation/kernel-parameters.txt
parentbb73c52bad3666997ed2ec83c0c80c3f8ef55008 (diff)
rcu: Eliminate panic when silly boot-time fanout specified
This commit loosens rcutree.rcu_fanout_leaf range checks and replaces a panic() with a fallback to compile-time values. This fallback is accompanied by a WARN_ON(), and both occur when the rcutree.rcu_fanout_leaf value is too small to accommodate the number of CPUs. For example, given the current four-level limit for the rcu_node tree, a system with more than 16 CPUs built with CONFIG_FANOUT=2 must have rcutree.rcu_fanout_leaf larger than 2. Reported-by: Peter Zijlstra <peterz@infradead.org> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Reviewed-by: Josh Triplett <josh@joshtriplett.org>
Diffstat (limited to 'Documentation/kernel-parameters.txt')
-rw-r--r--Documentation/kernel-parameters.txt9
1 files changed, 6 insertions, 3 deletions
diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index 22a4b687ea5b..23ec96877311 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -3074,9 +3074,12 @@ bytes respectively. Such letter suffixes can also be entirely omitted.
cache-to-cache transfer latencies.
rcutree.rcu_fanout_leaf= [KNL]
- Increase the number of CPUs assigned to each
- leaf rcu_node structure. Useful for very large
- systems.
+ Change the number of CPUs assigned to each
+ leaf rcu_node structure. Useful for very
+ large systems, which will choose the value 64,
+ and for NUMA systems with large remote-access
+ latencies, which will choose a value aligned
+ with the appropriate hardware boundaries.
rcutree.jiffies_till_sched_qs= [KNL]
Set required age in jiffies for a

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