linux-kernel - [RFC PATCH 2/3] timer: relax tick stop in idle entry

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Message-Id: <1446509428-5616-3-git-send-email-jacob.jun.pan@linux.intel.com>
Date:	Mon,  2 Nov 2015 16:10:27 -0800
From:	Jacob Pan <jacob.jun.pan@...ux.intel.com>
To:	Peter Zijlstra <peterz@...radead.org>
Cc:	Thomas Gleixner <tglx@...utronix.de>,
	LKML <linux-kernel@...r.kernel.org>,
	Arjan van de Ven <arjan@...ux.intel.com>,
	Paul Turner <pjt@...gle.com>, Len Brown <len.brown@...el.com>,
	Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>,
	Tim Chen <tim.c.chen@...ux.intel.com>,
	Andi Kleen <andi.kleen@...el.com>,
	Rafael Wysocki <rafael.j.wysocki@...el.com>,
	Jacob Pan <jacob.jun.pan@...ux.intel.com>
Subject: [RFC PATCH 2/3] timer: relax tick stop in idle entry

Upon entering idle, we can turn off tick if the next timeout
is exactly one tick away. Otherwise, we could enter inner idle loop
with tick still enabled, without resched set, the tick will continue
during idle therefore less optimal in terms of energy savings.

Signed-off-by: Jacob Pan <jacob.jun.pan@...ux.intel.com>
---
 kernel/time/tick-sched.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c
index 7c7ec45..bcadaab 100644
--- a/kernel/time/tick-sched.c
+++ b/kernel/time/tick-sched.c
@@ -606,7 +606,7 @@ static ktime_t tick_nohz_stop_sched_tick(struct tick_sched *ts,
 	 * restart it proper.
 	 */
 	delta = next_tick - basemono;
-	if (delta <= (u64)TICK_NSEC) {
+	if (delta < (u64)TICK_NSEC) {
 		tick.tv64 = 0;
 		if (!ts->tick_stopped)
 			goto out;
-- 
1.9.1

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