Commit-ID: b4be093fee0200789df59b6c90e2d099a20f55b3
Gitweb: http://git.kernel.org/tip/b4be093fee0200789df59b6c90e2d099a20f55b3
Author: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx>
AuthorDate: Mon, 25 Jun 2012 08:41:11 -0700
Committer: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx>
CommitDate: Sun, 23 Sep 2012 07:41:54 -0700
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 <mgalbraith@xxxxxxx>
Reported-by: Dimitri Sivanich <sivanich@xxxxxxx>
Signed-off-by: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx>
Reviewed-by: Josh Triplett <josh@xxxxxxxxxxxxxxxx>
---
kernel/rcutree.c | 1 +
1 files changed, 1 insertions(+), 0 deletions(-)
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)) {
--
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