linux-kernel - [PATCH] Make clocksource insert entry more efficiently

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Message-Id: <1461576028-2197-1-git-send-email-mnghuan@gmail.com>
Date:	Mon, 25 Apr 2016 17:20:28 +0800
From:	Minfei Huang <mnghuan@...il.com>
To:	john.stultz@...aro.org, tglx@...utronix.de
Cc:	linux-kernel@...r.kernel.org, Minfei Huang <mnghuan@...il.com>
Subject: [PATCH] Make clocksource insert entry more efficiently

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.

Signed-off-by: Minfei Huang <mnghuan@...il.com>
---
 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);
 }
 
-- 
2.6.3