[PATCH v1 11/16] thermal: gov_fair_share: Use .manage() callback instead of .throttle()

Rafael J. Wysocki
2024-04-10T17:44:59Z

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

The Fair Share governor tries very hard to be stateless and so it
calls get_trip_level() from fair_share_throttle() every time, even
though the number produced by this function for all of the trips
during a given thermal zone update is actually the same. Since
get_trip_level() walks all of the trips in the thermal zone every
time it is called, doing this may generate quite a bit of completely
useless overhead.

For this reason, make the governor use the new .manage() callback
instead of .throttle() which allows it to call get_trip_level() just
once and use the value computed by it to handle all of the trips.

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
---
drivers/thermal/gov_fair_share.c | 37 ++++++++++++++++++++++++++-----------
1 file changed, 26 insertions(+), 11 deletions(-)

Index: linux-pm/drivers/thermal/gov_fair_share.c
===================================================================
--- linux-pm.orig/drivers/thermal/gov_fair_share.c
+++ linux-pm/drivers/thermal/gov_fair_share.c
@@ -53,6 +53,7 @@ static long get_target_state(struct ther
* fair_share_throttle - throttles devices associated with the given zone
* @tz: thermal_zone_device
* @trip: trip point
+ * @trip_level: number of trips crossed by the zone temperature
*
* Throttling Logic: This uses three parameters to calculate the new
* throttle state of the cooling devices associated with the given zone.
@@ -61,22 +62,19 @@ static long get_target_state(struct ther
* P1. max_state: Maximum throttle state exposed by the cooling device.
* P2. percentage[i]/100:
* How 'effective' the 'i'th device is, in cooling the given zone.
- * P3. cur_trip_level/max_no_of_trips:
+ * P3. trip_level/max_no_of_trips:
* This describes the extent to which the devices should be throttled.
* We do not want to throttle too much when we trip a lower temperature,
* whereas the throttling is at full swing if we trip critical levels.
- * (Heavily assumes the trip points are in ascending order)
* new_state of cooling device = P3 * P2 * P1
*/
-static int fair_share_throttle(struct thermal_zone_device *tz,
- const struct thermal_trip *trip)
+static void fair_share_throttle(struct thermal_zone_device *tz,
+ const struct thermal_trip *trip,
+ int trip_level)
{
struct thermal_instance *instance;
int total_weight = 0;
int total_instance = 0;
- int cur_trip_level = get_trip_level(tz);
-
- lockdep_assert_held(&tz->lock);

list_for_each_entry(instance, &tz->thermal_instances, tz_node) {
if (instance->trip != trip)
@@ -99,18 +97,35 @@ static int fair_share_throttle(struct th
percentage = (instance->weight * 100) / total_weight;

instance->target = get_target_state(tz, cdev, percentage,
- cur_trip_level);
+ trip_level);

mutex_lock(&cdev->lock);
__thermal_cdev_update(cdev);
mutex_unlock(&cdev->lock);
}
+}

- return 0;
+static void fair_share_manage(struct thermal_zone_device *tz)
+{
+ int trip_level = get_trip_level(tz);
+ const struct thermal_trip_desc *td;
+
+ lockdep_assert_held(&tz->lock);
+
+ for_each_trip_desc(tz, td) {
+ const struct thermal_trip *trip = &td->trip;
+
+ if (trip->temperature == THERMAL_TEMP_INVALID ||
+ trip->type == THERMAL_TRIP_CRITICAL ||
+ trip->type == THERMAL_TRIP_HOT)
+ continue;
+
+ fair_share_throttle(tz, trip, trip_level);
+ }
}

static struct thermal_governor thermal_gov_fair_share = {
- .name = "fair_share",
- .throttle = fair_share_throttle,
+ .name = "fair_share",
+ .manage = fair_share_manage,
};
THERMAL_GOVERNOR_DECLARE(thermal_gov_fair_share);