linux-kernel - [PATCH for 6.13 v1 3/8] thermal: core: Build sorted lists instead of sorting them later

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Message-ID: <3316488.44csPzL39Z@rjwysocki.net>
Date: Tue, 10 Sep 2024 11:30:13 +0200
From: "Rafael J. Wysocki" <rjw@...ysocki.net>
To: Linux PM <linux-pm@...r.kernel.org>
Cc: LKML <linux-kernel@...r.kernel.org>,
 Daniel Lezcano <daniel.lezcano@...aro.org>,
 Lukasz Luba <lukasz.luba@....com>, Zhang Rui <rui.zhang@...el.com>
Subject:
 [PATCH for 6.13 v1 3/8] thermal: core: Build sorted lists instead of sorting
 them later

From: Rafael J. Wysocki <rafael.j.wysocki@...el.com>

Large numbers of trip points are not expected to be crossed in one go,
so quite likely it is more efficient to build a sorted list of crossed
trip points than to put them on an unsorted list and sort it later.

Moreover, trip points are often provided in ascending temperature order
during thermal zone registration. so they are naturally sorted anyway
and building a sorted list out of them is quite straightforward.

Accordingly, make handle_thermal_trip() maintain list ordering when
adding trip points to the lists and get rid of separate list sorting
in __thermal_zone_device_update().

No intentional functional impact.

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
---
 drivers/thermal/thermal_core.c |   33 ++++++++++++++++++---------------
 1 file changed, 18 insertions(+), 15 deletions(-)

Index: linux-pm/drivers/thermal/thermal_core.c
===================================================================
--- linux-pm.orig/drivers/thermal/thermal_core.c
+++ linux-pm/drivers/thermal/thermal_core.c
@@ -15,7 +15,6 @@
 #include <linux/slab.h>
 #include <linux/kdev_t.h>
 #include <linux/idr.h>
-#include <linux/list_sort.h>
 #include <linux/thermal.h>
 #include <linux/reboot.h>
 #include <linux/string.h>
@@ -421,6 +420,21 @@ static void handle_critical_trips(struct
 		tz->ops.hot(tz);
 }
 
+static void add_trip_to_sorted_list(struct thermal_trip_desc *td,
+				    struct list_head *list)
+{
+	struct thermal_trip_desc *entry;
+
+	/* Assume that the new entry is likely to be the last one. */
+	list_for_each_entry_reverse(entry, list, notify_list_node) {
+		if (entry->notify_temp <= td->notify_temp) {
+			list_add(&td->notify_list_node, &entry->notify_list_node);
+			return;
+		}
+	}
+	list_add(&td->notify_list_node, list);
+}
+
 static void handle_thermal_trip(struct thermal_zone_device *tz,
 				struct thermal_trip_desc *td,
 				struct list_head *way_up_list,
@@ -450,8 +464,8 @@ static void handle_thermal_trip(struct t
 		 * In that case, the trip temperature becomes the new threshold.
 		 */
 		if (tz->temperature < trip->temperature - trip->hysteresis) {
-			list_add(&td->notify_list_node, way_down_list);
 			td->notify_temp = trip->temperature - trip->hysteresis;
+			add_trip_to_sorted_list(td, way_down_list);
 
 			if (trip->type == THERMAL_TRIP_PASSIVE) {
 				tz->passive--;
@@ -466,8 +480,9 @@ static void handle_thermal_trip(struct t
 		 * if the zone temperature exceeds the trip one.  The new
 		 * threshold is then set to the low temperature of the trip.
 		 */
-		list_add_tail(&td->notify_list_node, way_up_list);
 		td->notify_temp = trip->temperature;
+		add_trip_to_sorted_list(td, way_up_list);
+
 		td->threshold -= trip->hysteresis;
 
 		if (trip->type == THERMAL_TRIP_PASSIVE)
@@ -531,16 +546,6 @@ static void thermal_trip_crossed(struct
 	thermal_governor_trip_crossed(governor, tz, trip, crossed_up);
 }
 
-static int thermal_trip_notify_cmp(void *not_used, const struct list_head *a,
-				   const struct list_head *b)
-{
-	struct thermal_trip_desc *tda = container_of(a, struct thermal_trip_desc,
-						     notify_list_node);
-	struct thermal_trip_desc *tdb = container_of(b, struct thermal_trip_desc,
-						     notify_list_node);
-	return tda->notify_temp - tdb->notify_temp;
-}
-
 void __thermal_zone_device_update(struct thermal_zone_device *tz,
 				  enum thermal_notify_event event)
 {
@@ -591,11 +596,9 @@ void __thermal_zone_device_update(struct
 
 	thermal_zone_set_trips(tz, low, high);
 
-	list_sort(NULL, &way_up_list, thermal_trip_notify_cmp);
 	list_for_each_entry(td, &way_up_list, notify_list_node)
 		thermal_trip_crossed(tz, &td->trip, governor, true);
 
-	list_sort(NULL, &way_down_list, thermal_trip_notify_cmp);
 	list_for_each_entry_reverse(td, &way_down_list, notify_list_node)
 		thermal_trip_crossed(tz, &td->trip, governor, false);