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Subject[PATCH RFC tip/core/rcu 5/5] rcu: Limit expedited helping to every 10 ms or every 4th GP
Date
From: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
---
kernel/rcu/tree.c | 15 ++++++++++++---
1 file changed, 12 insertions(+), 3 deletions(-)

diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index 308b6acb4260..247aa1120c4c 100644
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -3505,10 +3505,19 @@ void synchronize_sched_expedited(void)
!atomic_read(&rsp->expedited_need_qs));

rcu_exp_gp_seq_end(rsp);
- mutex_unlock(&rnp->exp_funnel_mutex);
smp_mb(); /* ensure subsequent action seen after grace period. */
- if (rsp->gp_kthread && rcu_gp_in_progress(rsp))
- wake_up(&rsp->gp_wq);
+ if (rsp->gp_kthread && rcu_gp_in_progress(rsp)) {
+ static unsigned long nextgp;
+ static unsigned long nextjiffy;
+
+ if (time_after_eq(jiffies, nextgp) ||
+ ULONG_CMP_GE(rsp->gpnum, nextgp)) {
+ nextgp = rsp->gpnum + 4;
+ nextjiffy = jiffies + 10;
+ wake_up(&rsp->gp_wq);
+ }
+ }
+ mutex_unlock(&rnp->exp_funnel_mutex);

put_online_cpus();
}
--
1.8.1.5


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