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| author | Paul E. McKenney <paulmck@linux.vnet.ibm.com> | 2015-07-31 08:28:35 -0700 |
|---|---|---|
| committer | Paul E. McKenney <paulmck@linux.vnet.ibm.com> | 2015-10-06 11:09:41 -0700 |
| commit | ee968ac61d5a3440b931375d81113e0eedfcb249 (patch) | |
| tree | ac6f4bc6727b19506941412b6d09c5fe44ca8b3d /Documentation/kernel-parameters.txt | |
| parent | bb73c52bad3666997ed2ec83c0c80c3f8ef55008 (diff) | |
| download | lwn-ee968ac61d5a3440b931375d81113e0eedfcb249.tar.gz lwn-ee968ac61d5a3440b931375d81113e0eedfcb249.zip | |
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.txt | 9 |
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 |