From f1f399d1281ea339a08469f7e58193624992f620 Mon Sep 17 00:00:00 2001 From: "Paul E. McKenney" Date: Sun, 17 Nov 2013 21:08:07 -0800 Subject: [PATCH] rcu: Optimize RCU_FAST_NO_HZ for RCU_NOCB_CPU_ALL If CONFIG_RCU_NOCB_CPU_ALL=y, then no CPU will ever have RCU callbacks because these callbacks will instead be handled by the rcuo kthreads. However, the current version of RCU_FAST_NO_HZ nevertheless checks for RCU callbacks. This commit therefore creates static inline implementations of rcu_prepare_for_idle() and rcu_cleanup_after_idle() that are no-ops when CONFIG_RCU_NOCB_CPU_ALL=y. Signed-off-by: Paul E. McKenney Reviewed-by: Josh Triplett --- kernel/rcu/tree_plugin.h | 7 +++++-- 1 file changed, 5 insertions(+), 2 deletions(-) diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h index 820b06aefbee..41afc3fbfb6c 100644 --- a/kernel/rcu/tree_plugin.h +++ b/kernel/rcu/tree_plugin.h @@ -1658,7 +1658,7 @@ extern int tick_nohz_active; * only if it has been awhile since the last time we did so. Afterwards, * if there are any callbacks ready for immediate invocation, return true. */ -static bool rcu_try_advance_all_cbs(void) +static bool __maybe_unused rcu_try_advance_all_cbs(void) { bool cbs_ready = false; struct rcu_data *rdp; @@ -1743,6 +1743,7 @@ int rcu_needs_cpu(int cpu, unsigned long *dj) */ static void rcu_prepare_for_idle(int cpu) { +#ifndef CONFIG_RCU_NOCB_CPU_ALL struct rcu_data *rdp; struct rcu_dynticks *rdtp = &per_cpu(rcu_dynticks, cpu); struct rcu_node *rnp; @@ -1794,6 +1795,7 @@ static void rcu_prepare_for_idle(int cpu) rcu_accelerate_cbs(rsp, rnp, rdp); raw_spin_unlock(&rnp->lock); /* irqs remain disabled. */ } +#endif /* #ifndef CONFIG_RCU_NOCB_CPU_ALL */ } /* @@ -1803,11 +1805,12 @@ static void rcu_prepare_for_idle(int cpu) */ static void rcu_cleanup_after_idle(int cpu) { - +#ifndef CONFIG_RCU_NOCB_CPU_ALL if (rcu_is_nocb_cpu(cpu)) return; if (rcu_try_advance_all_cbs()) invoke_rcu_core(); +#endif /* #ifndef CONFIG_RCU_NOCB_CPU_ALL */ } /* -- 2.39.5