The following commit has been merged into the core/rcu branch of tip: Commit-ID: 4d80b8e196fad9852050f3c8624eea09a6bbeada Gitweb: https://git.kernel.org/tip/4d80b8e196fad9852050f3c8624eea09a6bbeada Author: Paul E. McKenney <paulmck@xxxxxxxxxx> AuthorDate: Wed, 07 Apr 2021 15:21:32 -07:00 Committer: Paul E. McKenney <paulmck@xxxxxxxxxx> CommitterDate: Mon, 10 May 2021 16:22:54 -07:00 rcu: Restrict RCU_STRICT_GRACE_PERIOD to at most four CPUs Kernels built with CONFIG_RCU_STRICT_GRACE_PERIOD=y can experience significant lock contention due to RCU's resulting focus on ending grace periods as soon as possible. This is OK, but only if there are not very many CPUs. This commit therefore puts this Kconfig option off-limits to systems with more than four CPUs. Signed-off-by: Paul E. McKenney <paulmck@xxxxxxxxxx> --- kernel/rcu/Kconfig.debug | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/kernel/rcu/Kconfig.debug b/kernel/rcu/Kconfig.debug index 1942c1f..4fd6499 100644 --- a/kernel/rcu/Kconfig.debug +++ b/kernel/rcu/Kconfig.debug @@ -116,7 +116,7 @@ config RCU_EQS_DEBUG config RCU_STRICT_GRACE_PERIOD bool "Provide debug RCU implementation with short grace periods" - depends on DEBUG_KERNEL && RCU_EXPERT + depends on DEBUG_KERNEL && RCU_EXPERT && NR_CPUS <= 4 default n select PREEMPT_COUNT if PREEMPT=n help
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