Commit-ID: b8c78d3afc6aac1c722af3bec18959c6bd93231c Gitweb: http://git.kernel.org/tip/b8c78d3afc6aac1c722af3bec18959c6bd93231c Author: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx> AuthorDate: Fri, 3 Feb 2017 09:54:05 -0800 Committer: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx> CommitDate: Tue, 18 Apr 2017 11:38:18 -0700 rcu: Default RCU_FANOUT_LEAF to 16 unless explicitly changed If the RCU_EXPERT Kconfig option is not set (the default), then the RCU_FANOUT_LEAF Kconfig option will not be defined, which will cause the leaf-level rcu_node tree fanout to default to 32 on 32-bit systems and 64 on 64-bit systems. This can result in excessive lock contention. This commit therefore changes the computation of the leaf-level rcu_node tree fanout so that the result will be 16 unless an explicit Kconfig or kernel-boot setting says otherwise. Reported-by: Peter Zijlstra <peterz@xxxxxxxxxxxxx> Signed-off-by: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx> --- kernel/rcu/tree.h | 6 +----- 1 file changed, 1 insertion(+), 5 deletions(-) diff --git a/kernel/rcu/tree.h b/kernel/rcu/tree.h index d2f276f..376c01e 100644 --- a/kernel/rcu/tree.h +++ b/kernel/rcu/tree.h @@ -52,11 +52,7 @@ #ifdef CONFIG_RCU_FANOUT_LEAF #define RCU_FANOUT_LEAF CONFIG_RCU_FANOUT_LEAF #else /* #ifdef CONFIG_RCU_FANOUT_LEAF */ -# ifdef CONFIG_64BIT -# define RCU_FANOUT_LEAF 64 -# else -# define RCU_FANOUT_LEAF 32 -# endif +#define RCU_FANOUT_LEAF 16 #endif /* #else #ifdef CONFIG_RCU_FANOUT_LEAF */ #define RCU_FANOUT_1 (RCU_FANOUT_LEAF) -- To unsubscribe from this list: send the line "unsubscribe linux-tip-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
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