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Date: Fri, 3 Nov 2006 12:46:41 -0800 (PST)
From: Christoph Lameter <clameter@sgi.com>
To: akpm@osdl.org
Cc: Christoph Lameter <clameter@sgi.com>, linux-kernel@vger.kernel.org
Message-Id: <20061103204641.15739.87085.sendpatchset@schroedinger.engr.sgi.com>
In-Reply-To: <20061103204636.15739.74831.sendpatchset@schroedinger.engr.sgi.com>
References: <20061103204636.15739.74831.sendpatchset@schroedinger.engr.sgi.com>
Subject: [PATCH 1/7] Avoid taking rq lock in wake_priority_sleeper
Sender: linux-kernel-owner@vger.kernel.org
X-Mailing-List: linux-kernel@vger.kernel.org

Avoid taking the rq lock in wake_priority sleeper

Avoid taking the request queue lock in wake_priority_sleeper if
there are no running processes.

Signed-off-by: Christoph Lameter <clameter@sgi.com>

Index: linux-2.6.19-rc4-mm2/kernel/sched.c
===================================================================
--- linux-2.6.19-rc4-mm2.orig/kernel/sched.c	2006-11-02 17:31:05.964060772 -0600
+++ linux-2.6.19-rc4-mm2/kernel/sched.c	2006-11-03 12:51:15.281805162 -0600
@@ -2899,6 +2899,9 @@ static inline int wake_priority_sleeper(
 	int ret = 0;
 
 #ifdef CONFIG_SCHED_SMT
+	if (!rq->nr_running)
+		return 0;
+
 	spin_lock(&rq->lock);
 	/*
 	 * If an SMT sibling task has been put to sleep for priority