From b4be093fee0200789df59b6c90e2d099a20f55b3 Mon Sep 17 00:00:00 2001 From: "Paul E. McKenney" Date: Mon, 25 Jun 2012 08:41:11 -0700 Subject: [PATCH] rcu: Allow RCU quiescent-state forcing to be preempted RCU quiescent-state forcing is currently carried out without preemption points, which can result in excessive latency spikes on large systems (many hundreds or thousands of CPUs). This patch therefore inserts a voluntary preemption point into force_qs_rnp(), which should greatly reduce the magnitude of these spikes. Reported-by: Mike Galbraith Reported-by: Dimitri Sivanich Signed-off-by: Paul E. McKenney Reviewed-by: Josh Triplett --- kernel/rcutree.c | 1 + 1 file changed, 1 insertion(+) diff --git a/kernel/rcutree.c b/kernel/rcutree.c index 6182686..723e2e7 100644 --- a/kernel/rcutree.c +++ b/kernel/rcutree.c @@ -1767,6 +1767,7 @@ static void force_qs_rnp(struct rcu_state *rsp, int (*f)(struct rcu_data *)) struct rcu_node *rnp; rcu_for_each_leaf_node(rsp, rnp) { + cond_resched(); mask = 0; raw_spin_lock_irqsave(&rnp->lock, flags); if (!rcu_gp_in_progress(rsp)) { -- 2.7.4