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From: Gregory Haskins <ghaskins@novell.com>
To: mingo@elte.hu, a.p.zijlstra@chello.nl, tglx@linutronix.de,
	rostedt@goodmis.org, linux-rt-users@vger.kernel.org
Cc: linux-kernel@vger.kernel.org, bill.huey@gmail.com,
	kevin@hilman.org, cminyard@mvista.com, dsingleton@mvista.com,
	dwalker@mvista.com, npiggin@suse.de, dsaxena@plexity.net,
	ak@suse.de, pavel@ucw.cz, acme@redhat.com, gregkh@suse.de,
	sdietrich@novell.com, pmorreale@novell.com, mkohari@novell.com,
	ghaskins@novell.com
Subject: [(RT RFC) PATCH v2 8/9] adjust pi_lock usage in wakeup
Date: Mon, 25 Feb 2008 11:01:18 -0500	[thread overview]
Message-ID: <20080225160118.11268.47575.stgit@novell1.haskins.net> (raw)
In-Reply-To: <20080225155959.11268.35541.stgit@novell1.haskins.net>

From: Peter W.Morreale <pmorreale@novell.com>

In wakeup_next_waiter(), we take the pi_lock, and then find out whether
we have another waiter to add to the pending owner.  We can reduce
contention on the pi_lock for the pending owner if we first obtain the
pointer to the next waiter outside of the pi_lock.

This patch adds a measureable increase in throughput.

Signed-off-by: Peter W. Morreale <pmorreale@novell.com>
---

 kernel/rtmutex.c |   14 +++++++++-----
 1 files changed, 9 insertions(+), 5 deletions(-)

diff --git a/kernel/rtmutex.c b/kernel/rtmutex.c
index ea593e0..b81bbef 100644
--- a/kernel/rtmutex.c
+++ b/kernel/rtmutex.c
@@ -526,6 +526,7 @@ static void wakeup_next_waiter(struct rt_mutex *lock, int savestate)
 {
 	struct rt_mutex_waiter *waiter;
 	struct task_struct *pendowner;
+	struct rt_mutex_waiter *next;
 
 	spin_lock(&current->pi_lock);
 
@@ -587,6 +588,12 @@ static void wakeup_next_waiter(struct rt_mutex *lock, int savestate)
 	 * waiter with higher priority than pending-owner->normal_prio
 	 * is blocked on the unboosted (pending) owner.
 	 */
+
+	if (rt_mutex_has_waiters(lock))
+		next = rt_mutex_top_waiter(lock);
+	else
+		next = NULL;
+
 	spin_lock(&pendowner->pi_lock);
 
 	WARN_ON(!pendowner->pi_blocked_on);
@@ -595,12 +602,9 @@ static void wakeup_next_waiter(struct rt_mutex *lock, int savestate)
 
 	pendowner->pi_blocked_on = NULL;
 
-	if (rt_mutex_has_waiters(lock)) {
-		struct rt_mutex_waiter *next;
-
-		next = rt_mutex_top_waiter(lock);
+	if (next)
 		plist_add(&next->pi_list_entry, &pendowner->pi_waiters);
-	}
+
 	spin_unlock(&pendowner->pi_lock);
 }
 


  parent reply	other threads:[~2008-02-25 16:31 UTC|newest]

Thread overview: 36+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2008-02-25 16:00 [(RT RFC) PATCH v2 0/9] adaptive real-time locks Gregory Haskins
2008-02-25 16:00 ` [(RT RFC) PATCH v2 1/9] allow rt-mutex lock-stealing to include lateral priority Gregory Haskins
2008-03-03 15:13   ` Steven Rostedt
2008-03-03 15:41     ` [(RT RFC) PATCH v2 1/9] allow rt-mutex lock-stealing to includelateral priority Gregory Haskins
2008-03-03 15:55       ` Steven Rostedt
2008-03-03 15:55         ` [(RT RFC) PATCH v2 1/9] allow rt-mutex lock-stealing toincludelateral priority Gregory Haskins
2008-02-25 16:00 ` [(RT RFC) PATCH v2 2/9] sysctl for runtime-control of lateral mutex stealing Gregory Haskins
2008-02-25 21:53   ` Pavel Machek
2008-02-25 22:57     ` Sven-Thorsten Dietrich
2008-02-25 23:00       ` Pavel Machek
2008-02-25 23:40         ` Sven-Thorsten Dietrich
2008-02-26  1:15       ` Gregory Haskins
2008-02-25 16:00 ` [(RT RFC) PATCH v2 3/9] rearrange rt_spin_lock sleep Gregory Haskins
2008-02-25 21:54   ` Pavel Machek
2008-02-26  0:45     ` Gregory Haskins
2008-02-25 16:00 ` [(RT RFC) PATCH v2 4/9] optimize rt lock wakeup Gregory Haskins
2008-03-03 15:37   ` Steven Rostedt
2008-03-03 15:41     ` Gregory Haskins
2008-02-25 16:01 ` [(RT RFC) PATCH v2 5/9] adaptive real-time lock support Gregory Haskins
2008-02-25 22:03   ` Pavel Machek
2008-02-26  0:48     ` Gregory Haskins
2008-02-26 15:03     ` Gregory Haskins
2008-02-26 18:06       ` Pavel Machek
2008-02-26 18:01         ` Gregory Haskins
2008-02-25 16:01 ` [(RT RFC) PATCH v2 6/9] add a loop counter based timeout mechanism Gregory Haskins
2008-02-25 22:06   ` Pavel Machek
2008-02-25 22:19     ` Greg KH
2008-02-25 22:21       ` Pavel Machek
2008-02-25 22:39     ` Sven-Thorsten Dietrich
2008-02-26 15:09     ` Gregory Haskins
2008-02-25 16:01 ` [(RT RFC) PATCH v2 7/9] adaptive mutexes Gregory Haskins
2008-02-25 22:09   ` Pavel Machek
2008-02-26  0:52     ` Gregory Haskins
2008-02-25 16:01 ` Gregory Haskins [this message]
2008-02-25 22:10   ` [(RT RFC) PATCH v2 8/9] adjust pi_lock usage in wakeup Pavel Machek
2008-02-25 16:01 ` [(RT RFC) PATCH v2 9/9] remove the extra call to try_to_take_lock Gregory Haskins

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