| Message ID | 2170379.OBFZWjSADL@kreacher |
|---|---|
| State | New |
| Headers | show |
| Series | thermal: core: Redesign the governor interface | expand |
On 4/10/24 18:00, Rafael J. Wysocki wrote: > From: Rafael J. Wysocki <rafael.j.wysocki@intel.com> > > The computations carried out by fair_share_throttle() for each trip > point include at least one redundant integer division which introduces > superfluous rounding errors. Also the multiplications by 100 in it are > not really necessary and can be eliminated. > > Rearrange fair_share_throttle() to carry out only one integer division per > trip and only as many integer multiplications as necessary and rename one > variable in it (while at it). > > Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com> > --- > drivers/thermal/gov_fair_share.c | 32 +++++++++++++++----------------- > 1 file changed, 15 insertions(+), 17 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 > @@ -41,12 +41,6 @@ static int get_trip_level(struct thermal > return trip_level; > } > > -static long get_target_state(struct thermal_zone_device *tz, > - struct thermal_cooling_device *cdev, int percentage, int level) > -{ > - return (long)(percentage * level * cdev->max_state) / (100 * tz->num_trips); > -} > - > /** > * fair_share_throttle - throttles devices associated with the given zone > * @tz: thermal_zone_device > @@ -58,7 +52,7 @@ static long get_target_state(struct ther > * > * Parameters used for Throttling: > * P1. max_state: Maximum throttle state exposed by the cooling device. > - * P2. percentage[i]/100: > + * P2. weight[i]/total_weight: > * How 'effective' the 'i'th device is, in cooling the given zone. > * P3. trip_level/max_no_of_trips: > * This describes the extent to which the devices should be throttled. > @@ -72,30 +66,34 @@ static void fair_share_throttle(struct t > { > struct thermal_instance *instance; > int total_weight = 0; > - int total_instance = 0; > + int nr_instances = 0; > > list_for_each_entry(instance, &tz->thermal_instances, tz_node) { > if (instance->trip != trip) > continue; > > total_weight += instance->weight; > - total_instance++; > + nr_instances++; > } > > list_for_each_entry(instance, &tz->thermal_instances, tz_node) { > - int percentage; > struct thermal_cooling_device *cdev = instance->cdev; > + u64 dividend; > + u32 divisor; > > if (instance->trip != trip) > continue; > > - if (!total_weight) > - percentage = 100 / total_instance; > - else > - percentage = (instance->weight * 100) / total_weight; > - > - instance->target = get_target_state(tz, cdev, percentage, > - trip_level); > + dividend = trip_level; > + dividend *= cdev->max_state; > + divisor = tz->num_trips; > + if (total_weight) { > + dividend *= instance->weight; > + divisor *= total_weight; > + } else { > + divisor *= nr_instances; > + } > + instance->target = div_u64(dividend, divisor); > > mutex_lock(&cdev->lock); > __thermal_cdev_update(cdev); > > > Reviewed-by: Lukasz Luba <lukasz.luba@arm.com>
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 @@ -41,12 +41,6 @@ static int get_trip_level(struct thermal return trip_level; } -static long get_target_state(struct thermal_zone_device *tz, - struct thermal_cooling_device *cdev, int percentage, int level) -{ - return (long)(percentage * level * cdev->max_state) / (100 * tz->num_trips); -} - /** * fair_share_throttle - throttles devices associated with the given zone * @tz: thermal_zone_device @@ -58,7 +52,7 @@ static long get_target_state(struct ther * * Parameters used for Throttling: * P1. max_state: Maximum throttle state exposed by the cooling device. - * P2. percentage[i]/100: + * P2. weight[i]/total_weight: * How 'effective' the 'i'th device is, in cooling the given zone. * P3. trip_level/max_no_of_trips: * This describes the extent to which the devices should be throttled. @@ -72,30 +66,34 @@ static void fair_share_throttle(struct t { struct thermal_instance *instance; int total_weight = 0; - int total_instance = 0; + int nr_instances = 0; list_for_each_entry(instance, &tz->thermal_instances, tz_node) { if (instance->trip != trip) continue; total_weight += instance->weight; - total_instance++; + nr_instances++; } list_for_each_entry(instance, &tz->thermal_instances, tz_node) { - int percentage; struct thermal_cooling_device *cdev = instance->cdev; + u64 dividend; + u32 divisor; if (instance->trip != trip) continue; - if (!total_weight) - percentage = 100 / total_instance; - else - percentage = (instance->weight * 100) / total_weight; - - instance->target = get_target_state(tz, cdev, percentage, - trip_level); + dividend = trip_level; + dividend *= cdev->max_state; + divisor = tz->num_trips; + if (total_weight) { + dividend *= instance->weight; + divisor *= total_weight; + } else { + divisor *= nr_instances; + } + instance->target = div_u64(dividend, divisor); mutex_lock(&cdev->lock); __thermal_cdev_update(cdev);