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

Lukasz Luba
2024-04-19T18:28:45Z

On 4/10/24 17:57, Rafael J. Wysocki wrote:
> 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);
>
>
>

LGTM

Reviewed-by: Lukasz Luba <lukasz.luba@arm.com>