linux-kernel - [PATCH] pm_qos: remove unnecessary list-traversal

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Date:	Tue,  1 Jun 2010 10:52:11 +0200
From:	florian@...kler.org
To:	"Rafael J. Wysocki" <rjw@...k.pl>
Cc:	640e9920@...il.com, markgross@...gnar.org,
	Arve Hj?nnev?g <arve@...roid.com>,
	Alan Stern <stern@...land.harvard.edu>,
	Peter Zijlstra <peterz@...radead.org>,
	Linux PM <linux-pm@...ts.linux-foundation.org>,
	Brian Swetland <swetland@...gle.com>,
	Alan Cox <alan@...rguk.ukuu.org.uk>,
	Matthew Garrett <mjg59@...f.ucam.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	LKML <linux-kernel@...r.kernel.org>, Ingo Molnar <mingo@...e.hu>,
	Florian Mickler <florian@...kler.org>
Subject: [PATCH] pm_qos: remove unnecessary list-traversal

The new extreme value is only depending on the old extreme value and
the changed value.

Signed-off-by: Florian Mickler <florian@...kler.org>
---
This version actually compiles...  :)

 kernel/pm_qos_params.c |   19 +++++++++++++++++--
 1 files changed, 17 insertions(+), 2 deletions(-)

diff --git a/kernel/pm_qos_params.c b/kernel/pm_qos_params.c
index f42d3f7..3ae94e1 100644
--- a/kernel/pm_qos_params.c
+++ b/kernel/pm_qos_params.c
@@ -136,6 +136,16 @@ static s32 min_compare(s32 v1, s32 v2)
 }
 
 
+static void update_target_val(int pm_qos_class, s32 val)
+{
+	s32 extreme_value;
+	s32 new_value;
+	extreme_value = atomic_read(&pm_qos_array[pm_qos_class]->target_value);
+	new_value = pm_qos_array[pm_qos_class]->comparitor(val,extreme_value);
+	if (extreme_value != new_value)
+		atomic_set(&pm_qos_array[pm_qos_class]->target_value,new_value);
+}
+
 static void update_target(int pm_qos_class)
 {
 	s32 extreme_value;
@@ -253,19 +263,24 @@ void pm_qos_update_request(struct pm_qos_request_list *pm_qos_req,
 	s32 temp;
 
 	if (pm_qos_req) { /*guard against callers passing in null */
+		int target = pm_qos_req->pm_qos_class;
 		spin_lock_irqsave(&pm_qos_lock, flags);
 		if (new_value == PM_QOS_DEFAULT_VALUE)
-			temp = pm_qos_array[pm_qos_req->pm_qos_class]->default_value;
+			temp = pm_qos_array[target]->default_value;
 		else
 			temp = new_value;
 
 		if (temp != pm_qos_req->value) {
 			pending_update = 1;
 			pm_qos_req->value = temp;
+			update_target_val(target,temp);
 		}
 		spin_unlock_irqrestore(&pm_qos_lock, flags);
+
 		if (pending_update)
-			update_target(pm_qos_req->pm_qos_class);
+			blocking_notifier_call_chain(
+				pm_qos_array[target]->notifiers,
+					(unsigned long) temp, NULL);
 	}
 }
 EXPORT_SYMBOL_GPL(pm_qos_update_request);
-- 
1.7.1

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