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[rcu,7/8] rcu: Round FAST_NO_HZ lazy timeout to nearest second

Message ID 1339129615-1795-7-git-send-email-paulmck@linux.vnet.ibm.com
State New
Headers show

Commit Message

Paul E. McKenney June 8, 2012, 4:26 a.m. UTC 
From: "Paul E. McKenney" <paul.mckenney@linaro.org>

Currently, if several CPUs in the same package have all lazy RCU
callbacks, their wakeups will be uncorrelated.  If all the CPUs are in the
same power domain (as is often the case), this will result in unnecessary
power-ups of the package.  This commit therefore uses round_jiffies()
to round the timeouts to a second boundary, increasing the odds that
they can be coalesced with each other or with other timeouts.

Signed-off-by: Paul E. McKenney <paul.mckenney@linaro.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
---
 kernel/rcutree_plugin.h |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)
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Patch

diff --git a/kernel/rcutree_plugin.h b/kernel/rcutree_plugin.h
index 5271a02..4451362b 100644
--- a/kernel/rcutree_plugin.h
+++ b/kernel/rcutree_plugin.h
@@ -2182,7 +2182,7 @@  static void rcu_prepare_for_idle(int cpu)
 					   jiffies + RCU_IDLE_GP_DELAY;
 		} else {
 			rdtp->idle_gp_timer_expires =
-					   jiffies + RCU_IDLE_LAZY_GP_DELAY;
+				round_jiffies(jiffies + RCU_IDLE_LAZY_GP_DELAY);
 			trace_rcu_prep_idle("Dyntick with lazy callbacks");
 		}
 		tp = &rdtp->idle_gp_timer;