linux-kernel - [PATCH 1/6] clocksource: Make clocksource insert entry more efficient

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Date:	Mon, 20 Jun 2016 12:56:20 -0700
From:	John Stultz <john.stultz@...aro.org>
To:	lkml <linux-kernel@...r.kernel.org>
Cc:	Minfei Huang <mnghuan@...il.com>,
	Prarit Bhargava <prarit@...hat.com>,
	Richard Cochran <richardcochran@...il.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...nel.org>,
	John Stultz <john.stultz@...aro.org>
Subject: [PATCH 1/6] clocksource: Make clocksource insert entry more efficient

From: Minfei Huang <mnghuan@...il.com>

In clocksource_enqueue(), it is unnecessary to continue looping
the list, if we find there is an entry that the value of rating
is smaller than the new one. It is safe to be out the loop,
because all of entry are inserted in descending order.

Cc: Prarit Bhargava <prarit@...hat.com>
Cc: Richard Cochran <richardcochran@...il.com>
Cc: Thomas Gleixner <tglx@...utronix.de>
Cc: Ingo Molnar <mingo@...nel.org>
Signed-off-by: Minfei Huang <mnghuan@...il.com>
Signed-off-by: John Stultz <john.stultz@...aro.org>
---
 kernel/time/clocksource.c | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/kernel/time/clocksource.c b/kernel/time/clocksource.c
index 56ece14..6a5a310 100644
--- a/kernel/time/clocksource.c
+++ b/kernel/time/clocksource.c
@@ -669,10 +669,12 @@ static void clocksource_enqueue(struct clocksource *cs)
 	struct list_head *entry = &clocksource_list;
 	struct clocksource *tmp;
 
-	list_for_each_entry(tmp, &clocksource_list, list)
+	list_for_each_entry(tmp, &clocksource_list, list) {
 		/* Keep track of the place, where to insert */
-		if (tmp->rating >= cs->rating)
-			entry = &tmp->list;
+		if (tmp->rating < cs->rating)
+			break;
+		entry = &tmp->list;
+	}
 	list_add(&cs->list, entry);
 }
 
-- 
1.9.1