[PATCH 0/2 v5] unlink misfit task from cpu overutilized

[PATCH 0/2 v5] unlink misfit task from cpu overutilized

[Vincent Guittot]

unlink misfit task detection from cpu overutilized and use the new -1 value
returned by util_fits_cpu() to extend the search for the best CPU.
Remove capacity inversion detection that is covered by these changes.

Changes since v4:
- Added patch 2 to remove capacity inversion detection

Vincent Guittot (2):
  sched/fair: unlink misfit task from cpu overutilized
  sched/fair: Remove capacity inversion detection

 kernel/sched/fair.c  | 189 ++++++++++++++++++++-----------------------
 kernel/sched/sched.h |  19 -----
 2 files changed, 87 insertions(+), 121 deletions(-)

-- 
2.34.1

[PATCH 1/2 v5] sched/fair: unlink misfit task from cpu overutilized

[Vincent Guittot]

By taking into account uclamp_min, the 1:1 relation between task misfit
and cpu overutilized is no more true as a task with a small util_avg may
not fit a high capacity cpu because of uclamp_min constraint.

Add a new state in util_fits_cpu() to reflect the case that task would fit
a CPU except for the uclamp_min hint which is a performance requirement.

Use -1 to reflect that a CPU doesn't fit only because of uclamp_min so we
can use this new value to take additional action to select the best CPU
that doesn't match uclamp_min hint.

When util_fits_cpu() returns -1, we will continue to look for a possible
CPU with better performance, which replaces Capacity Inversion detection
with capacity_orig_of() - thermal_load_avg to detect a capacity inversion.

Signed-off-by: Vincent Guittot <vincent.guittot@linaro.org>
Tested-by: Kajetan Puchalski <kajetan.puchalski@arm.com>
Reviewed-and-tested-by: Qais Yousef <qyousef@layalina.io>
Reviewed-by: Dietmar Eggemann <dietmar.eggemann@arm.com>
---

Change since v4:
- Add more details in commit message
- Fix typo
- Add Tag

 kernel/sched/fair.c | 105 ++++++++++++++++++++++++++++++++++----------
 1 file changed, 82 insertions(+), 23 deletions(-)

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 7c46485d65d7..074742f107c0 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -4561,8 +4561,8 @@ static inline int util_fits_cpu(unsigned long util,
 	 * handle the case uclamp_min > uclamp_max.
 	 */
 	uclamp_min = min(uclamp_min, uclamp_max);
-	if (util < uclamp_min && capacity_orig != SCHED_CAPACITY_SCALE)
-		fits = fits && (uclamp_min <= capacity_orig_thermal);
+	if (fits && (util < uclamp_min) && (uclamp_min > capacity_orig_thermal))
+		return -1;
 
 	return fits;
 }
@@ -4572,7 +4572,11 @@ static inline int task_fits_cpu(struct task_struct *p, int cpu)
 	unsigned long uclamp_min = uclamp_eff_value(p, UCLAMP_MIN);
 	unsigned long uclamp_max = uclamp_eff_value(p, UCLAMP_MAX);
 	unsigned long util = task_util_est(p);
-	return util_fits_cpu(util, uclamp_min, uclamp_max, cpu);
+	/*
+	 * Return true only if the cpu fully fits the task requirements, which
+	 * include the utilization but also the performance hints.
+	 */
+	return (util_fits_cpu(util, uclamp_min, uclamp_max, cpu) > 0);
 }
 
 static inline void update_misfit_status(struct task_struct *p, struct rq *rq)
@@ -6138,6 +6142,7 @@ static inline bool cpu_overutilized(int cpu)
 	unsigned long rq_util_min = uclamp_rq_get(cpu_rq(cpu), UCLAMP_MIN);
 	unsigned long rq_util_max = uclamp_rq_get(cpu_rq(cpu), UCLAMP_MAX);
 
+	/* Return true only if the utilization doesn't fit CPU's capacity */
 	return !util_fits_cpu(cpu_util_cfs(cpu), rq_util_min, rq_util_max, cpu);
 }
 
@@ -6931,6 +6936,7 @@ static int
 select_idle_capacity(struct task_struct *p, struct sched_domain *sd, int target)
 {
 	unsigned long task_util, util_min, util_max, best_cap = 0;
+	int fits, best_fits = 0;
 	int cpu, best_cpu = -1;
 	struct cpumask *cpus;
 
@@ -6946,12 +6952,28 @@ select_idle_capacity(struct task_struct *p, struct sched_domain *sd, int target)
 
 		if (!available_idle_cpu(cpu) && !sched_idle_cpu(cpu))
 			continue;
-		if (util_fits_cpu(task_util, util_min, util_max, cpu))
+
+		fits = util_fits_cpu(task_util, util_min, util_max, cpu);
+
+		/* This CPU fits with all requirements */
+		if (fits > 0)
 			return cpu;
+		/*
+		 * Only the min performance hint (i.e. uclamp_min) doesn't fit.
+		 * Look for the CPU with best capacity.
+		 */
+		else if (fits < 0)
+			cpu_cap = capacity_orig_of(cpu) - thermal_load_avg(cpu_rq(cpu));
 
-		if (cpu_cap > best_cap) {
+		/*
+		 * First, select CPU which fits better (-1 being better than 0).
+		 * Then, select the one with best capacity at same level.
+		 */
+		if ((fits < best_fits) ||
+		    ((fits == best_fits) && (cpu_cap > best_cap))) {
 			best_cap = cpu_cap;
 			best_cpu = cpu;
+			best_fits = fits;
 		}
 	}
 
@@ -6964,7 +6986,11 @@ static inline bool asym_fits_cpu(unsigned long util,
 				 int cpu)
 {
 	if (sched_asym_cpucap_active())
-		return util_fits_cpu(util, util_min, util_max, cpu);
+		/*
+		 * Return true only if the cpu fully fits the task requirements
+		 * which include the utilization and the performance hints.
+		 */
+		return (util_fits_cpu(util, util_min, util_max, cpu) > 0);
 
 	return true;
 }
@@ -7331,6 +7357,9 @@ static int find_energy_efficient_cpu(struct task_struct *p, int prev_cpu)
 	unsigned long p_util_max = uclamp_is_used() ? uclamp_eff_value(p, UCLAMP_MAX) : 1024;
 	struct root_domain *rd = this_rq()->rd;
 	int cpu, best_energy_cpu, target = -1;
+	int prev_fits = -1, best_fits = -1;
+	unsigned long best_thermal_cap = 0;
+	unsigned long prev_thermal_cap = 0;
 	struct sched_domain *sd;
 	struct perf_domain *pd;
 	struct energy_env eenv;
@@ -7366,6 +7395,7 @@ static int find_energy_efficient_cpu(struct task_struct *p, int prev_cpu)
 		unsigned long prev_spare_cap = 0;
 		int max_spare_cap_cpu = -1;
 		unsigned long base_energy;
+		int fits, max_fits = -1;
 
 		cpumask_and(cpus, perf_domain_span(pd), cpu_online_mask);
 
@@ -7415,7 +7445,9 @@ static int find_energy_efficient_cpu(struct task_struct *p, int prev_cpu)
 				util_min = max(rq_util_min, p_util_min);
 				util_max = max(rq_util_max, p_util_max);
 			}
-			if (!util_fits_cpu(util, util_min, util_max, cpu))
+
+			fits = util_fits_cpu(util, util_min, util_max, cpu);
+			if (!fits)
 				continue;
 
 			lsub_positive(&cpu_cap, util);
@@ -7423,7 +7455,9 @@ static int find_energy_efficient_cpu(struct task_struct *p, int prev_cpu)
 			if (cpu == prev_cpu) {
 				/* Always use prev_cpu as a candidate. */
 				prev_spare_cap = cpu_cap;
-			} else if (cpu_cap > max_spare_cap) {
+				prev_fits = fits;
+			} else if ((fits > max_fits) ||
+				   ((fits == max_fits) && (cpu_cap > max_spare_cap))) {
 				/*
 				 * Find the CPU with the maximum spare capacity
 				 * among the remaining CPUs in the performance
@@ -7431,6 +7465,7 @@ static int find_energy_efficient_cpu(struct task_struct *p, int prev_cpu)
 				 */
 				max_spare_cap = cpu_cap;
 				max_spare_cap_cpu = cpu;
+				max_fits = fits;
 			}
 		}
 
@@ -7449,26 +7484,50 @@ static int find_energy_efficient_cpu(struct task_struct *p, int prev_cpu)
 			if (prev_delta < base_energy)
 				goto unlock;
 			prev_delta -= base_energy;
+			prev_thermal_cap = cpu_thermal_cap;
 			best_delta = min(best_delta, prev_delta);
 		}
 
 		/* Evaluate the energy impact of using max_spare_cap_cpu. */
 		if (max_spare_cap_cpu >= 0 && max_spare_cap > prev_spare_cap) {
+			/* Current best energy cpu fits better */
+			if (max_fits < best_fits)
+				continue;
+
+			/*
+			 * Both don't fit performance hint (i.e. uclamp_min)
+			 * but best energy cpu has better capacity.
+			 */
+			if ((max_fits < 0) &&
+			    (cpu_thermal_cap <= best_thermal_cap))
+				continue;
+
 			cur_delta = compute_energy(&eenv, pd, cpus, p,
 						   max_spare_cap_cpu);
 			/* CPU utilization has changed */
 			if (cur_delta < base_energy)
 				goto unlock;
 			cur_delta -= base_energy;
-			if (cur_delta < best_delta) {
-				best_delta = cur_delta;
-				best_energy_cpu = max_spare_cap_cpu;
-			}
+
+			/*
+			 * Both fit for the task but best energy cpu has lower
+			 * energy impact.
+			 */
+			if ((max_fits > 0) && (best_fits > 0) &&
+			    (cur_delta >= best_delta))
+				continue;
+
+			best_delta = cur_delta;
+			best_energy_cpu = max_spare_cap_cpu;
+			best_fits = max_fits;
+			best_thermal_cap = cpu_thermal_cap;
 		}
 	}
 	rcu_read_unlock();
 
-	if (best_delta < prev_delta)
+	if ((best_fits > prev_fits) ||
+	    ((best_fits > 0) && (best_delta < prev_delta)) ||
+	    ((best_fits < 0) && (best_thermal_cap > prev_thermal_cap)))
 		target = best_energy_cpu;
 
 	return target;
@@ -10271,24 +10330,23 @@ static struct sched_group *find_busiest_group(struct lb_env *env)
 	 */
 	update_sd_lb_stats(env, &sds);
 
-	if (sched_energy_enabled()) {
-		struct root_domain *rd = env->dst_rq->rd;
-
-		if (rcu_dereference(rd->pd) && !READ_ONCE(rd->overutilized))
-			goto out_balanced;
-	}
-
-	local = &sds.local_stat;
-	busiest = &sds.busiest_stat;
-
 	/* There is no busy sibling group to pull tasks from */
 	if (!sds.busiest)
 		goto out_balanced;
 
+	busiest = &sds.busiest_stat;
+
 	/* Misfit tasks should be dealt with regardless of the avg load */
 	if (busiest->group_type == group_misfit_task)
 		goto force_balance;
 
+	if (sched_energy_enabled()) {
+		struct root_domain *rd = env->dst_rq->rd;
+
+		if (rcu_dereference(rd->pd) && !READ_ONCE(rd->overutilized))
+			goto out_balanced;
+	}
+
 	/* ASYM feature bypasses nice load balance check */
 	if (busiest->group_type == group_asym_packing)
 		goto force_balance;
@@ -10301,6 +10359,7 @@ static struct sched_group *find_busiest_group(struct lb_env *env)
 	if (busiest->group_type == group_imbalanced)
 		goto force_balance;
 
+	local = &sds.local_stat;
 	/*
 	 * If the local group is busier than the selected busiest group
 	 * don't try and pull any tasks.
-- 
2.34.1

[PATCH 2/2 v5] sched/fair: Remove capacity inversion detection

[Vincent Guittot]

Remove the capacity inversion detection which is now handled by
util_fits_cpu() returning -1 when we need to continue to look for a
potential CPU with better performance.

This ends up almost reverting patches below except for some comments:
commit da07d2f9c153 ("sched/fair: Fixes for capacity inversion detection")
commit aa69c36f31aa ("sched/fair: Consider capacity inversion in util_fits_cpu()")
commit 44c7b80bffc3 ("sched/fair: Detect capacity inversion")

Signed-off-by: Vincent Guittot <vincent.guittot@linaro.org>
---
 kernel/sched/fair.c  | 84 +++-----------------------------------------
 kernel/sched/sched.h | 19 ----------
 2 files changed, 5 insertions(+), 98 deletions(-)

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 074742f107c0..c6c8e7f52935 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -4476,17 +4476,9 @@ static inline int util_fits_cpu(unsigned long util,
 	 *
 	 * For uclamp_max, we can tolerate a drop in performance level as the
 	 * goal is to cap the task. So it's okay if it's getting less.
-	 *
-	 * In case of capacity inversion we should honour the inverted capacity
-	 * for both uclamp_min and uclamp_max all the time.
 	 */
-	capacity_orig = cpu_in_capacity_inversion(cpu);
-	if (capacity_orig) {
-		capacity_orig_thermal = capacity_orig;
-	} else {
-		capacity_orig = capacity_orig_of(cpu);
-		capacity_orig_thermal = capacity_orig - arch_scale_thermal_pressure(cpu);
-	}
+	capacity_orig = capacity_orig_of(cpu);
+	capacity_orig_thermal = capacity_orig - arch_scale_thermal_pressure(cpu);
 
 	/*
 	 * We want to force a task to fit a cpu as implied by uclamp_max.
@@ -9027,82 +9019,16 @@ static unsigned long scale_rt_capacity(int cpu)
 
 static void update_cpu_capacity(struct sched_domain *sd, int cpu)
 {
-	unsigned long capacity_orig = arch_scale_cpu_capacity(cpu);
 	unsigned long capacity = scale_rt_capacity(cpu);
 	struct sched_group *sdg = sd->groups;
-	struct rq *rq = cpu_rq(cpu);
 
-	rq->cpu_capacity_orig = capacity_orig;
+	cpu_rq(cpu)->cpu_capacity_orig = arch_scale_cpu_capacity(cpu);
 
 	if (!capacity)
 		capacity = 1;
 
-	rq->cpu_capacity = capacity;
-
-	/*
-	 * Detect if the performance domain is in capacity inversion state.
-	 *
-	 * Capacity inversion happens when another perf domain with equal or
-	 * lower capacity_orig_of() ends up having higher capacity than this
-	 * domain after subtracting thermal pressure.
-	 *
-	 * We only take into account thermal pressure in this detection as it's
-	 * the only metric that actually results in *real* reduction of
-	 * capacity due to performance points (OPPs) being dropped/become
-	 * unreachable due to thermal throttling.
-	 *
-	 * We assume:
-	 *   * That all cpus in a perf domain have the same capacity_orig
-	 *     (same uArch).
-	 *   * Thermal pressure will impact all cpus in this perf domain
-	 *     equally.
-	 */
-	if (sched_energy_enabled()) {
-		unsigned long inv_cap = capacity_orig - thermal_load_avg(rq);
-		struct perf_domain *pd;
-
-		rcu_read_lock();
-
-		pd = rcu_dereference(rq->rd->pd);
-		rq->cpu_capacity_inverted = 0;
-
-		for (; pd; pd = pd->next) {
-			struct cpumask *pd_span = perf_domain_span(pd);
-			unsigned long pd_cap_orig, pd_cap;
-
-			/* We can't be inverted against our own pd */
-			if (cpumask_test_cpu(cpu_of(rq), pd_span))
-				continue;
-
-			cpu = cpumask_any(pd_span);
-			pd_cap_orig = arch_scale_cpu_capacity(cpu);
-
-			if (capacity_orig < pd_cap_orig)
-				continue;
-
-			/*
-			 * handle the case of multiple perf domains have the
-			 * same capacity_orig but one of them is under higher
-			 * thermal pressure. We record it as capacity
-			 * inversion.
-			 */
-			if (capacity_orig == pd_cap_orig) {
-				pd_cap = pd_cap_orig - thermal_load_avg(cpu_rq(cpu));
-
-				if (pd_cap > inv_cap) {
-					rq->cpu_capacity_inverted = inv_cap;
-					break;
-				}
-			} else if (pd_cap_orig > inv_cap) {
-				rq->cpu_capacity_inverted = inv_cap;
-				break;
-			}
-		}
-
-		rcu_read_unlock();
-	}
-
-	trace_sched_cpu_capacity_tp(rq);
+	cpu_rq(cpu)->cpu_capacity = capacity;
+	trace_sched_cpu_capacity_tp(cpu_rq(cpu));
 
 	sdg->sgc->capacity = capacity;
 	sdg->sgc->min_capacity = capacity;
diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
index 1072502976df..3e8df6d31c1e 100644
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -1044,7 +1044,6 @@ struct rq {
 
 	unsigned long		cpu_capacity;
 	unsigned long		cpu_capacity_orig;
-	unsigned long		cpu_capacity_inverted;
 
 	struct balance_callback *balance_callback;
 
@@ -2899,24 +2898,6 @@ static inline unsigned long capacity_orig_of(int cpu)
 	return cpu_rq(cpu)->cpu_capacity_orig;
 }
 
-/*
- * Returns inverted capacity if the CPU is in capacity inversion state.
- * 0 otherwise.
- *
- * Capacity inversion detection only considers thermal impact where actual
- * performance points (OPPs) gets dropped.
- *
- * Capacity inversion state happens when another performance domain that has
- * equal or lower capacity_orig_of() becomes effectively larger than the perf
- * domain this CPU belongs to due to thermal pressure throttling it hard.
- *
- * See comment in update_cpu_capacity().
- */
-static inline unsigned long cpu_in_capacity_inversion(int cpu)
-{
-	return cpu_rq(cpu)->cpu_capacity_inverted;
-}
-
 /**
  * enum cpu_util_type - CPU utilization type
  * @FREQUENCY_UTIL:	Utilization used to select frequency
-- 
2.34.1

Re: [PATCH 0/2 v5] unlink misfit task from cpu overutilized

[Rafael J. Wysocki]

On Wed, Feb 1, 2023 at 3:36 PM Vincent Guittot
<vincent.guittot@linaro.org> wrote:
>
> unlink misfit task detection from cpu overutilized and use the new -1 value
> returned by util_fits_cpu() to extend the search for the best CPU.
> Remove capacity inversion detection that is covered by these changes.
>
> Changes since v4:
> - Added patch 2 to remove capacity inversion detection
>
> Vincent Guittot (2):
>   sched/fair: unlink misfit task from cpu overutilized
>   sched/fair: Remove capacity inversion detection
>
>  kernel/sched/fair.c  | 189 ++++++++++++++++++++-----------------------
>  kernel/sched/sched.h |  19 -----
>  2 files changed, 87 insertions(+), 121 deletions(-)
>
> --

Acked-by: Rafael J. Wysocki <rafael@kernel.org>

for the series.

Re: [PATCH 2/2 v5] sched/fair: Remove capacity inversion detection

[Qais Yousef]

On 02/01/23 15:36, Vincent Guittot wrote:
> Remove the capacity inversion detection which is now handled by
> util_fits_cpu() returning -1 when we need to continue to look for a
> potential CPU with better performance.
> 
> This ends up almost reverting patches below except for some comments:

nit: I think this comment must be removed/reworeded though

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 691a2f9c4efa..c6c8e7f52935 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -4476,10 +4476,6 @@ static inline int util_fits_cpu(unsigned long util,
         *
         * For uclamp_max, we can tolerate a drop in performance level as the
         * goal is to cap the task. So it's okay if it's getting less.
-        *
-        * In case of capacity inversion, which is not handled yet, we should
-        * honour the inverted capacity for both uclamp_min and uclamp_max all
-        * the time.
         */
        capacity_orig = capacity_orig_of(cpu);
        capacity_orig_thermal = capacity_orig - arch_scale_thermal_pressure(cpu);

> commit da07d2f9c153 ("sched/fair: Fixes for capacity inversion detection")
> commit aa69c36f31aa ("sched/fair: Consider capacity inversion in util_fits_cpu()")
> commit 44c7b80bffc3 ("sched/fair: Detect capacity inversion")
> 
> Signed-off-by: Vincent Guittot <vincent.guittot@linaro.org>

Apart from that, LGTM.

Reviewed-by: Qais Yousef <qyousef@layalina.io>


Thanks!

--
Qais Yousef

> ---
>  kernel/sched/fair.c  | 84 +++-----------------------------------------
>  kernel/sched/sched.h | 19 ----------
>  2 files changed, 5 insertions(+), 98 deletions(-)
> 
> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
> index 074742f107c0..c6c8e7f52935 100644
> --- a/kernel/sched/fair.c
> +++ b/kernel/sched/fair.c
> @@ -4476,17 +4476,9 @@ static inline int util_fits_cpu(unsigned long util,
>  	 *
>  	 * For uclamp_max, we can tolerate a drop in performance level as the
>  	 * goal is to cap the task. So it's okay if it's getting less.
> -	 *
> -	 * In case of capacity inversion we should honour the inverted capacity
> -	 * for both uclamp_min and uclamp_max all the time.
>  	 */
> -	capacity_orig = cpu_in_capacity_inversion(cpu);
> -	if (capacity_orig) {
> -		capacity_orig_thermal = capacity_orig;
> -	} else {
> -		capacity_orig = capacity_orig_of(cpu);
> -		capacity_orig_thermal = capacity_orig - arch_scale_thermal_pressure(cpu);
> -	}
> +	capacity_orig = capacity_orig_of(cpu);
> +	capacity_orig_thermal = capacity_orig - arch_scale_thermal_pressure(cpu);
>  
>  	/*
>  	 * We want to force a task to fit a cpu as implied by uclamp_max.
> @@ -9027,82 +9019,16 @@ static unsigned long scale_rt_capacity(int cpu)
>  
>  static void update_cpu_capacity(struct sched_domain *sd, int cpu)
>  {
> -	unsigned long capacity_orig = arch_scale_cpu_capacity(cpu);
>  	unsigned long capacity = scale_rt_capacity(cpu);
>  	struct sched_group *sdg = sd->groups;
> -	struct rq *rq = cpu_rq(cpu);
>  
> -	rq->cpu_capacity_orig = capacity_orig;
> +	cpu_rq(cpu)->cpu_capacity_orig = arch_scale_cpu_capacity(cpu);
>  
>  	if (!capacity)
>  		capacity = 1;
>  
> -	rq->cpu_capacity = capacity;
> -
> -	/*
> -	 * Detect if the performance domain is in capacity inversion state.
> -	 *
> -	 * Capacity inversion happens when another perf domain with equal or
> -	 * lower capacity_orig_of() ends up having higher capacity than this
> -	 * domain after subtracting thermal pressure.
> -	 *
> -	 * We only take into account thermal pressure in this detection as it's
> -	 * the only metric that actually results in *real* reduction of
> -	 * capacity due to performance points (OPPs) being dropped/become
> -	 * unreachable due to thermal throttling.
> -	 *
> -	 * We assume:
> -	 *   * That all cpus in a perf domain have the same capacity_orig
> -	 *     (same uArch).
> -	 *   * Thermal pressure will impact all cpus in this perf domain
> -	 *     equally.
> -	 */
> -	if (sched_energy_enabled()) {
> -		unsigned long inv_cap = capacity_orig - thermal_load_avg(rq);
> -		struct perf_domain *pd;
> -
> -		rcu_read_lock();
> -
> -		pd = rcu_dereference(rq->rd->pd);
> -		rq->cpu_capacity_inverted = 0;
> -
> -		for (; pd; pd = pd->next) {
> -			struct cpumask *pd_span = perf_domain_span(pd);
> -			unsigned long pd_cap_orig, pd_cap;
> -
> -			/* We can't be inverted against our own pd */
> -			if (cpumask_test_cpu(cpu_of(rq), pd_span))
> -				continue;
> -
> -			cpu = cpumask_any(pd_span);
> -			pd_cap_orig = arch_scale_cpu_capacity(cpu);
> -
> -			if (capacity_orig < pd_cap_orig)
> -				continue;
> -
> -			/*
> -			 * handle the case of multiple perf domains have the
> -			 * same capacity_orig but one of them is under higher
> -			 * thermal pressure. We record it as capacity
> -			 * inversion.
> -			 */
> -			if (capacity_orig == pd_cap_orig) {
> -				pd_cap = pd_cap_orig - thermal_load_avg(cpu_rq(cpu));
> -
> -				if (pd_cap > inv_cap) {
> -					rq->cpu_capacity_inverted = inv_cap;
> -					break;
> -				}
> -			} else if (pd_cap_orig > inv_cap) {
> -				rq->cpu_capacity_inverted = inv_cap;
> -				break;
> -			}
> -		}
> -
> -		rcu_read_unlock();
> -	}
> -
> -	trace_sched_cpu_capacity_tp(rq);
> +	cpu_rq(cpu)->cpu_capacity = capacity;
> +	trace_sched_cpu_capacity_tp(cpu_rq(cpu));
>  
>  	sdg->sgc->capacity = capacity;
>  	sdg->sgc->min_capacity = capacity;
> diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
> index 1072502976df..3e8df6d31c1e 100644
> --- a/kernel/sched/sched.h
> +++ b/kernel/sched/sched.h
> @@ -1044,7 +1044,6 @@ struct rq {
>  
>  	unsigned long		cpu_capacity;
>  	unsigned long		cpu_capacity_orig;
> -	unsigned long		cpu_capacity_inverted;
>  
>  	struct balance_callback *balance_callback;
>  
> @@ -2899,24 +2898,6 @@ static inline unsigned long capacity_orig_of(int cpu)
>  	return cpu_rq(cpu)->cpu_capacity_orig;
>  }
>  
> -/*
> - * Returns inverted capacity if the CPU is in capacity inversion state.
> - * 0 otherwise.
> - *
> - * Capacity inversion detection only considers thermal impact where actual
> - * performance points (OPPs) gets dropped.
> - *
> - * Capacity inversion state happens when another performance domain that has
> - * equal or lower capacity_orig_of() becomes effectively larger than the perf
> - * domain this CPU belongs to due to thermal pressure throttling it hard.
> - *
> - * See comment in update_cpu_capacity().
> - */
> -static inline unsigned long cpu_in_capacity_inversion(int cpu)
> -{
> -	return cpu_rq(cpu)->cpu_capacity_inverted;
> -}
> -
>  /**
>   * enum cpu_util_type - CPU utilization type
>   * @FREQUENCY_UTIL:	Utilization used to select frequency
> -- 
> 2.34.1
> 

Re: [PATCH 2/2 v5] sched/fair: Remove capacity inversion detection

[Vincent Guittot]

On Sat, 4 Feb 2023 at 19:42, Qais Yousef <qyousef@layalina.io> wrote:
>
> On 02/01/23 15:36, Vincent Guittot wrote:
> > Remove the capacity inversion detection which is now handled by
> > util_fits_cpu() returning -1 when we need to continue to look for a
> > potential CPU with better performance.
> >
> > This ends up almost reverting patches below except for some comments:
>
> nit: I think this comment must be removed/reworeded though

This comment has already been removed. That's why I said almost revert
except for some comments in the commit message

>
> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
> index 691a2f9c4efa..c6c8e7f52935 100644
> --- a/kernel/sched/fair.c
> +++ b/kernel/sched/fair.c
> @@ -4476,10 +4476,6 @@ static inline int util_fits_cpu(unsigned long util,
>          *
>          * For uclamp_max, we can tolerate a drop in performance level as the
>          * goal is to cap the task. So it's okay if it's getting less.
> -        *
> -        * In case of capacity inversion, which is not handled yet, we should
> -        * honour the inverted capacity for both uclamp_min and uclamp_max all
> -        * the time.
>          */
>         capacity_orig = capacity_orig_of(cpu);
>         capacity_orig_thermal = capacity_orig - arch_scale_thermal_pressure(cpu);
>
> > commit da07d2f9c153 ("sched/fair: Fixes for capacity inversion detection")
> > commit aa69c36f31aa ("sched/fair: Consider capacity inversion in util_fits_cpu()")
> > commit 44c7b80bffc3 ("sched/fair: Detect capacity inversion")
> >
> > Signed-off-by: Vincent Guittot <vincent.guittot@linaro.org>
>
> Apart from that, LGTM.
>
> Reviewed-by: Qais Yousef <qyousef@layalina.io>

Thanks

>
>
> Thanks!
>
> --
> Qais Yousef
>
> > ---
> >  kernel/sched/fair.c  | 84 +++-----------------------------------------
> >  kernel/sched/sched.h | 19 ----------
> >  2 files changed, 5 insertions(+), 98 deletions(-)
> >
> > diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
> > index 074742f107c0..c6c8e7f52935 100644
> > --- a/kernel/sched/fair.c
> > +++ b/kernel/sched/fair.c
> > @@ -4476,17 +4476,9 @@ static inline int util_fits_cpu(unsigned long util,
> >        *
> >        * For uclamp_max, we can tolerate a drop in performance level as the
> >        * goal is to cap the task. So it's okay if it's getting less.
> > -      *
> > -      * In case of capacity inversion we should honour the inverted capacity
> > -      * for both uclamp_min and uclamp_max all the time.
> >        */
> > -     capacity_orig = cpu_in_capacity_inversion(cpu);
> > -     if (capacity_orig) {
> > -             capacity_orig_thermal = capacity_orig;
> > -     } else {
> > -             capacity_orig = capacity_orig_of(cpu);
> > -             capacity_orig_thermal = capacity_orig - arch_scale_thermal_pressure(cpu);
> > -     }
> > +     capacity_orig = capacity_orig_of(cpu);
> > +     capacity_orig_thermal = capacity_orig - arch_scale_thermal_pressure(cpu);
> >
> >       /*
> >        * We want to force a task to fit a cpu as implied by uclamp_max.
> > @@ -9027,82 +9019,16 @@ static unsigned long scale_rt_capacity(int cpu)
> >
> >  static void update_cpu_capacity(struct sched_domain *sd, int cpu)
> >  {
> > -     unsigned long capacity_orig = arch_scale_cpu_capacity(cpu);
> >       unsigned long capacity = scale_rt_capacity(cpu);
> >       struct sched_group *sdg = sd->groups;
> > -     struct rq *rq = cpu_rq(cpu);
> >
> > -     rq->cpu_capacity_orig = capacity_orig;
> > +     cpu_rq(cpu)->cpu_capacity_orig = arch_scale_cpu_capacity(cpu);
> >
> >       if (!capacity)
> >               capacity = 1;
> >
> > -     rq->cpu_capacity = capacity;
> > -
> > -     /*
> > -      * Detect if the performance domain is in capacity inversion state.
> > -      *
> > -      * Capacity inversion happens when another perf domain with equal or
> > -      * lower capacity_orig_of() ends up having higher capacity than this
> > -      * domain after subtracting thermal pressure.
> > -      *
> > -      * We only take into account thermal pressure in this detection as it's
> > -      * the only metric that actually results in *real* reduction of
> > -      * capacity due to performance points (OPPs) being dropped/become
> > -      * unreachable due to thermal throttling.
> > -      *
> > -      * We assume:
> > -      *   * That all cpus in a perf domain have the same capacity_orig
> > -      *     (same uArch).
> > -      *   * Thermal pressure will impact all cpus in this perf domain
> > -      *     equally.
> > -      */
> > -     if (sched_energy_enabled()) {
> > -             unsigned long inv_cap = capacity_orig - thermal_load_avg(rq);
> > -             struct perf_domain *pd;
> > -
> > -             rcu_read_lock();
> > -
> > -             pd = rcu_dereference(rq->rd->pd);
> > -             rq->cpu_capacity_inverted = 0;
> > -
> > -             for (; pd; pd = pd->next) {
> > -                     struct cpumask *pd_span = perf_domain_span(pd);
> > -                     unsigned long pd_cap_orig, pd_cap;
> > -
> > -                     /* We can't be inverted against our own pd */
> > -                     if (cpumask_test_cpu(cpu_of(rq), pd_span))
> > -                             continue;
> > -
> > -                     cpu = cpumask_any(pd_span);
> > -                     pd_cap_orig = arch_scale_cpu_capacity(cpu);
> > -
> > -                     if (capacity_orig < pd_cap_orig)
> > -                             continue;
> > -
> > -                     /*
> > -                      * handle the case of multiple perf domains have the
> > -                      * same capacity_orig but one of them is under higher
> > -                      * thermal pressure. We record it as capacity
> > -                      * inversion.
> > -                      */
> > -                     if (capacity_orig == pd_cap_orig) {
> > -                             pd_cap = pd_cap_orig - thermal_load_avg(cpu_rq(cpu));
> > -
> > -                             if (pd_cap > inv_cap) {
> > -                                     rq->cpu_capacity_inverted = inv_cap;
> > -                                     break;
> > -                             }
> > -                     } else if (pd_cap_orig > inv_cap) {
> > -                             rq->cpu_capacity_inverted = inv_cap;
> > -                             break;
> > -                     }
> > -             }
> > -
> > -             rcu_read_unlock();
> > -     }
> > -
> > -     trace_sched_cpu_capacity_tp(rq);
> > +     cpu_rq(cpu)->cpu_capacity = capacity;
> > +     trace_sched_cpu_capacity_tp(cpu_rq(cpu));
> >
> >       sdg->sgc->capacity = capacity;
> >       sdg->sgc->min_capacity = capacity;
> > diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
> > index 1072502976df..3e8df6d31c1e 100644
> > --- a/kernel/sched/sched.h
> > +++ b/kernel/sched/sched.h
> > @@ -1044,7 +1044,6 @@ struct rq {
> >
> >       unsigned long           cpu_capacity;
> >       unsigned long           cpu_capacity_orig;
> > -     unsigned long           cpu_capacity_inverted;
> >
> >       struct balance_callback *balance_callback;
> >
> > @@ -2899,24 +2898,6 @@ static inline unsigned long capacity_orig_of(int cpu)
> >       return cpu_rq(cpu)->cpu_capacity_orig;
> >  }
> >
> > -/*
> > - * Returns inverted capacity if the CPU is in capacity inversion state.
> > - * 0 otherwise.
> > - *
> > - * Capacity inversion detection only considers thermal impact where actual
> > - * performance points (OPPs) gets dropped.
> > - *
> > - * Capacity inversion state happens when another performance domain that has
> > - * equal or lower capacity_orig_of() becomes effectively larger than the perf
> > - * domain this CPU belongs to due to thermal pressure throttling it hard.
> > - *
> > - * See comment in update_cpu_capacity().
> > - */
> > -static inline unsigned long cpu_in_capacity_inversion(int cpu)
> > -{
> > -     return cpu_rq(cpu)->cpu_capacity_inverted;
> > -}
> > -
> >  /**
> >   * enum cpu_util_type - CPU utilization type
> >   * @FREQUENCY_UTIL:  Utilization used to select frequency
> > --
> > 2.34.1
> >

Re: [PATCH 2/2 v5] sched/fair: Remove capacity inversion detection

[Qais Yousef]

On 02/05/23 18:29, Vincent Guittot wrote:
> On Sat, 4 Feb 2023 at 19:42, Qais Yousef <qyousef@layalina.io> wrote:
> >
> > On 02/01/23 15:36, Vincent Guittot wrote:
> > > Remove the capacity inversion detection which is now handled by
> > > util_fits_cpu() returning -1 when we need to continue to look for a
> > > potential CPU with better performance.
> > >
> > > This ends up almost reverting patches below except for some comments:
> >
> > nit: I think this comment must be removed/reworeded though
> 
> This comment has already been removed. That's why I said almost revert
> except for some comments in the commit message

Oh, my diff cmd had the wrong order then, sorry.

> 
> >
> > diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
> > index 691a2f9c4efa..c6c8e7f52935 100644
> > --- a/kernel/sched/fair.c
> > +++ b/kernel/sched/fair.c
> > @@ -4476,10 +4476,6 @@ static inline int util_fits_cpu(unsigned long util,
> >          *
> >          * For uclamp_max, we can tolerate a drop in performance level as the
> >          * goal is to cap the task. So it's okay if it's getting less.
> > -        *
> > -        * In case of capacity inversion, which is not handled yet, we should
> > -        * honour the inverted capacity for both uclamp_min and uclamp_max all
> > -        * the time.
> >          */
> >         capacity_orig = capacity_orig_of(cpu);
> >         capacity_orig_thermal = capacity_orig - arch_scale_thermal_pressure(cpu);
> >
> > > commit da07d2f9c153 ("sched/fair: Fixes for capacity inversion detection")
> > > commit aa69c36f31aa ("sched/fair: Consider capacity inversion in util_fits_cpu()")
> > > commit 44c7b80bffc3 ("sched/fair: Detect capacity inversion")
> > >
> > > Signed-off-by: Vincent Guittot <vincent.guittot@linaro.org>
> >
> > Apart from that, LGTM.
> >
> > Reviewed-by: Qais Yousef <qyousef@layalina.io>
> 
> Thanks
> 
> >
> >
> > Thanks!
> >
> > --
> > Qais Yousef
> >
> > > ---
> > >  kernel/sched/fair.c  | 84 +++-----------------------------------------
> > >  kernel/sched/sched.h | 19 ----------
> > >  2 files changed, 5 insertions(+), 98 deletions(-)
> > >
> > > diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
> > > index 074742f107c0..c6c8e7f52935 100644
> > > --- a/kernel/sched/fair.c
> > > +++ b/kernel/sched/fair.c
> > > @@ -4476,17 +4476,9 @@ static inline int util_fits_cpu(unsigned long util,
> > >        *
> > >        * For uclamp_max, we can tolerate a drop in performance level as the
> > >        * goal is to cap the task. So it's okay if it's getting less.
> > > -      *
> > > -      * In case of capacity inversion we should honour the inverted capacity
> > > -      * for both uclamp_min and uclamp_max all the time.
> > >        */
> > > -     capacity_orig = cpu_in_capacity_inversion(cpu);
> > > -     if (capacity_orig) {
> > > -             capacity_orig_thermal = capacity_orig;
> > > -     } else {
> > > -             capacity_orig = capacity_orig_of(cpu);
> > > -             capacity_orig_thermal = capacity_orig - arch_scale_thermal_pressure(cpu);
> > > -     }
> > > +     capacity_orig = capacity_orig_of(cpu);
> > > +     capacity_orig_thermal = capacity_orig - arch_scale_thermal_pressure(cpu);
> > >
> > >       /*
> > >        * We want to force a task to fit a cpu as implied by uclamp_max.
> > > @@ -9027,82 +9019,16 @@ static unsigned long scale_rt_capacity(int cpu)
> > >
> > >  static void update_cpu_capacity(struct sched_domain *sd, int cpu)
> > >  {
> > > -     unsigned long capacity_orig = arch_scale_cpu_capacity(cpu);
> > >       unsigned long capacity = scale_rt_capacity(cpu);
> > >       struct sched_group *sdg = sd->groups;
> > > -     struct rq *rq = cpu_rq(cpu);
> > >
> > > -     rq->cpu_capacity_orig = capacity_orig;
> > > +     cpu_rq(cpu)->cpu_capacity_orig = arch_scale_cpu_capacity(cpu);
> > >
> > >       if (!capacity)
> > >               capacity = 1;
> > >
> > > -     rq->cpu_capacity = capacity;
> > > -
> > > -     /*
> > > -      * Detect if the performance domain is in capacity inversion state.
> > > -      *
> > > -      * Capacity inversion happens when another perf domain with equal or
> > > -      * lower capacity_orig_of() ends up having higher capacity than this
> > > -      * domain after subtracting thermal pressure.
> > > -      *
> > > -      * We only take into account thermal pressure in this detection as it's
> > > -      * the only metric that actually results in *real* reduction of
> > > -      * capacity due to performance points (OPPs) being dropped/become
> > > -      * unreachable due to thermal throttling.
> > > -      *
> > > -      * We assume:
> > > -      *   * That all cpus in a perf domain have the same capacity_orig
> > > -      *     (same uArch).
> > > -      *   * Thermal pressure will impact all cpus in this perf domain
> > > -      *     equally.
> > > -      */
> > > -     if (sched_energy_enabled()) {
> > > -             unsigned long inv_cap = capacity_orig - thermal_load_avg(rq);
> > > -             struct perf_domain *pd;
> > > -
> > > -             rcu_read_lock();
> > > -
> > > -             pd = rcu_dereference(rq->rd->pd);
> > > -             rq->cpu_capacity_inverted = 0;
> > > -
> > > -             for (; pd; pd = pd->next) {
> > > -                     struct cpumask *pd_span = perf_domain_span(pd);
> > > -                     unsigned long pd_cap_orig, pd_cap;
> > > -
> > > -                     /* We can't be inverted against our own pd */
> > > -                     if (cpumask_test_cpu(cpu_of(rq), pd_span))
> > > -                             continue;
> > > -
> > > -                     cpu = cpumask_any(pd_span);
> > > -                     pd_cap_orig = arch_scale_cpu_capacity(cpu);
> > > -
> > > -                     if (capacity_orig < pd_cap_orig)
> > > -                             continue;
> > > -
> > > -                     /*
> > > -                      * handle the case of multiple perf domains have the
> > > -                      * same capacity_orig but one of them is under higher
> > > -                      * thermal pressure. We record it as capacity
> > > -                      * inversion.
> > > -                      */
> > > -                     if (capacity_orig == pd_cap_orig) {
> > > -                             pd_cap = pd_cap_orig - thermal_load_avg(cpu_rq(cpu));
> > > -
> > > -                             if (pd_cap > inv_cap) {
> > > -                                     rq->cpu_capacity_inverted = inv_cap;
> > > -                                     break;
> > > -                             }
> > > -                     } else if (pd_cap_orig > inv_cap) {
> > > -                             rq->cpu_capacity_inverted = inv_cap;
> > > -                             break;
> > > -                     }
> > > -             }
> > > -
> > > -             rcu_read_unlock();
> > > -     }
> > > -
> > > -     trace_sched_cpu_capacity_tp(rq);
> > > +     cpu_rq(cpu)->cpu_capacity = capacity;
> > > +     trace_sched_cpu_capacity_tp(cpu_rq(cpu));
> > >
> > >       sdg->sgc->capacity = capacity;
> > >       sdg->sgc->min_capacity = capacity;
> > > diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
> > > index 1072502976df..3e8df6d31c1e 100644
> > > --- a/kernel/sched/sched.h
> > > +++ b/kernel/sched/sched.h
> > > @@ -1044,7 +1044,6 @@ struct rq {
> > >
> > >       unsigned long           cpu_capacity;
> > >       unsigned long           cpu_capacity_orig;
> > > -     unsigned long           cpu_capacity_inverted;
> > >
> > >       struct balance_callback *balance_callback;
> > >
> > > @@ -2899,24 +2898,6 @@ static inline unsigned long capacity_orig_of(int cpu)
> > >       return cpu_rq(cpu)->cpu_capacity_orig;
> > >  }
> > >
> > > -/*
> > > - * Returns inverted capacity if the CPU is in capacity inversion state.
> > > - * 0 otherwise.
> > > - *
> > > - * Capacity inversion detection only considers thermal impact where actual
> > > - * performance points (OPPs) gets dropped.
> > > - *
> > > - * Capacity inversion state happens when another performance domain that has
> > > - * equal or lower capacity_orig_of() becomes effectively larger than the perf
> > > - * domain this CPU belongs to due to thermal pressure throttling it hard.
> > > - *
> > > - * See comment in update_cpu_capacity().
> > > - */
> > > -static inline unsigned long cpu_in_capacity_inversion(int cpu)
> > > -{
> > > -     return cpu_rq(cpu)->cpu_capacity_inverted;
> > > -}
> > > -
> > >  /**
> > >   * enum cpu_util_type - CPU utilization type
> > >   * @FREQUENCY_UTIL:  Utilization used to select frequency
> > > --
> > > 2.34.1
> > >

[tip: sched/core] sched/fair: Remove capacity inversion detection

[tip-bot2 for Vincent Guittot]

The following commit has been merged into the sched/core branch of tip:

Commit-ID:     a2e90611b9f425adbbfcdaa5b5e49958ddf6f61b
Gitweb:        https://git.kernel.org/tip/a2e90611b9f425adbbfcdaa5b5e49958ddf6f61b
Author:        Vincent Guittot <vincent.guittot@linaro.org>
AuthorDate:    Wed, 01 Feb 2023 15:36:28 +01:00
Committer:     Peter Zijlstra <peterz@infradead.org>
CommitterDate: Sat, 11 Feb 2023 11:18:09 +01:00

sched/fair: Remove capacity inversion detection

Remove the capacity inversion detection which is now handled by
util_fits_cpu() returning -1 when we need to continue to look for a
potential CPU with better performance.

This ends up almost reverting patches below except for some comments:
commit da07d2f9c153 ("sched/fair: Fixes for capacity inversion detection")
commit aa69c36f31aa ("sched/fair: Consider capacity inversion in util_fits_cpu()")
commit 44c7b80bffc3 ("sched/fair: Detect capacity inversion")

Signed-off-by: Vincent Guittot <vincent.guittot@linaro.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/r/20230201143628.270912-3-vincent.guittot@linaro.org
---
 kernel/sched/fair.c  | 84 ++-----------------------------------------
 kernel/sched/sched.h | 19 +----------
 2 files changed, 5 insertions(+), 98 deletions(-)

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 074742f..c6c8e7f 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -4476,17 +4476,9 @@ static inline int util_fits_cpu(unsigned long util,
 	 *
 	 * For uclamp_max, we can tolerate a drop in performance level as the
 	 * goal is to cap the task. So it's okay if it's getting less.
-	 *
-	 * In case of capacity inversion we should honour the inverted capacity
-	 * for both uclamp_min and uclamp_max all the time.
 	 */
-	capacity_orig = cpu_in_capacity_inversion(cpu);
-	if (capacity_orig) {
-		capacity_orig_thermal = capacity_orig;
-	} else {
-		capacity_orig = capacity_orig_of(cpu);
-		capacity_orig_thermal = capacity_orig - arch_scale_thermal_pressure(cpu);
-	}
+	capacity_orig = capacity_orig_of(cpu);
+	capacity_orig_thermal = capacity_orig - arch_scale_thermal_pressure(cpu);
 
 	/*
 	 * We want to force a task to fit a cpu as implied by uclamp_max.
@@ -9027,82 +9019,16 @@ static unsigned long scale_rt_capacity(int cpu)
 
 static void update_cpu_capacity(struct sched_domain *sd, int cpu)
 {
-	unsigned long capacity_orig = arch_scale_cpu_capacity(cpu);
 	unsigned long capacity = scale_rt_capacity(cpu);
 	struct sched_group *sdg = sd->groups;
-	struct rq *rq = cpu_rq(cpu);
 
-	rq->cpu_capacity_orig = capacity_orig;
+	cpu_rq(cpu)->cpu_capacity_orig = arch_scale_cpu_capacity(cpu);
 
 	if (!capacity)
 		capacity = 1;
 
-	rq->cpu_capacity = capacity;
-
-	/*
-	 * Detect if the performance domain is in capacity inversion state.
-	 *
-	 * Capacity inversion happens when another perf domain with equal or
-	 * lower capacity_orig_of() ends up having higher capacity than this
-	 * domain after subtracting thermal pressure.
-	 *
-	 * We only take into account thermal pressure in this detection as it's
-	 * the only metric that actually results in *real* reduction of
-	 * capacity due to performance points (OPPs) being dropped/become
-	 * unreachable due to thermal throttling.
-	 *
-	 * We assume:
-	 *   * That all cpus in a perf domain have the same capacity_orig
-	 *     (same uArch).
-	 *   * Thermal pressure will impact all cpus in this perf domain
-	 *     equally.
-	 */
-	if (sched_energy_enabled()) {
-		unsigned long inv_cap = capacity_orig - thermal_load_avg(rq);
-		struct perf_domain *pd;
-
-		rcu_read_lock();
-
-		pd = rcu_dereference(rq->rd->pd);
-		rq->cpu_capacity_inverted = 0;
-
-		for (; pd; pd = pd->next) {
-			struct cpumask *pd_span = perf_domain_span(pd);
-			unsigned long pd_cap_orig, pd_cap;
-
-			/* We can't be inverted against our own pd */
-			if (cpumask_test_cpu(cpu_of(rq), pd_span))
-				continue;
-
-			cpu = cpumask_any(pd_span);
-			pd_cap_orig = arch_scale_cpu_capacity(cpu);
-
-			if (capacity_orig < pd_cap_orig)
-				continue;
-
-			/*
-			 * handle the case of multiple perf domains have the
-			 * same capacity_orig but one of them is under higher
-			 * thermal pressure. We record it as capacity
-			 * inversion.
-			 */
-			if (capacity_orig == pd_cap_orig) {
-				pd_cap = pd_cap_orig - thermal_load_avg(cpu_rq(cpu));
-
-				if (pd_cap > inv_cap) {
-					rq->cpu_capacity_inverted = inv_cap;
-					break;
-				}
-			} else if (pd_cap_orig > inv_cap) {
-				rq->cpu_capacity_inverted = inv_cap;
-				break;
-			}
-		}
-
-		rcu_read_unlock();
-	}
-
-	trace_sched_cpu_capacity_tp(rq);
+	cpu_rq(cpu)->cpu_capacity = capacity;
+	trace_sched_cpu_capacity_tp(cpu_rq(cpu));
 
 	sdg->sgc->capacity = capacity;
 	sdg->sgc->min_capacity = capacity;
diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
index 1072502..3e8df6d 100644
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -1044,7 +1044,6 @@ struct rq {
 
 	unsigned long		cpu_capacity;
 	unsigned long		cpu_capacity_orig;
-	unsigned long		cpu_capacity_inverted;
 
 	struct balance_callback *balance_callback;
 
@@ -2899,24 +2898,6 @@ static inline unsigned long capacity_orig_of(int cpu)
 	return cpu_rq(cpu)->cpu_capacity_orig;
 }
 
-/*
- * Returns inverted capacity if the CPU is in capacity inversion state.
- * 0 otherwise.
- *
- * Capacity inversion detection only considers thermal impact where actual
- * performance points (OPPs) gets dropped.
- *
- * Capacity inversion state happens when another performance domain that has
- * equal or lower capacity_orig_of() becomes effectively larger than the perf
- * domain this CPU belongs to due to thermal pressure throttling it hard.
- *
- * See comment in update_cpu_capacity().
- */
-static inline unsigned long cpu_in_capacity_inversion(int cpu)
-{
-	return cpu_rq(cpu)->cpu_capacity_inverted;
-}
-
 /**
  * enum cpu_util_type - CPU utilization type
  * @FREQUENCY_UTIL:	Utilization used to select frequency

[tip: sched/core] sched/fair: unlink misfit task from cpu overutilized

[tip-bot2 for Vincent Guittot]

The following commit has been merged into the sched/core branch of tip:

Commit-ID:     e5ed0550c04c5469ecdc1634d8aa18c8609590f0
Gitweb:        https://git.kernel.org/tip/e5ed0550c04c5469ecdc1634d8aa18c8609590f0
Author:        Vincent Guittot <vincent.guittot@linaro.org>
AuthorDate:    Wed, 01 Feb 2023 15:36:27 +01:00
Committer:     Peter Zijlstra <peterz@infradead.org>
CommitterDate: Sat, 11 Feb 2023 11:18:09 +01:00

sched/fair: unlink misfit task from cpu overutilized

By taking into account uclamp_min, the 1:1 relation between task misfit
and cpu overutilized is no more true as a task with a small util_avg may
not fit a high capacity cpu because of uclamp_min constraint.

Add a new state in util_fits_cpu() to reflect the case that task would fit
a CPU except for the uclamp_min hint which is a performance requirement.

Use -1 to reflect that a CPU doesn't fit only because of uclamp_min so we
can use this new value to take additional action to select the best CPU
that doesn't match uclamp_min hint.

When util_fits_cpu() returns -1, we will continue to look for a possible
CPU with better performance, which replaces Capacity Inversion detection
with capacity_orig_of() - thermal_load_avg to detect a capacity inversion.

Signed-off-by: Vincent Guittot <vincent.guittot@linaro.org>
Reviewed-and-tested-by: Qais Yousef <qyousef@layalina.io>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Dietmar Eggemann <dietmar.eggemann@arm.com>
Tested-by: Kajetan Puchalski <kajetan.puchalski@arm.com>
Link: https://lore.kernel.org/r/20230201143628.270912-2-vincent.guittot@linaro.org
---
 kernel/sched/fair.c | 105 +++++++++++++++++++++++++++++++++----------
 1 file changed, 82 insertions(+), 23 deletions(-)

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 7c46485..074742f 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -4561,8 +4561,8 @@ static inline int util_fits_cpu(unsigned long util,
 	 * handle the case uclamp_min > uclamp_max.
 	 */
 	uclamp_min = min(uclamp_min, uclamp_max);
-	if (util < uclamp_min && capacity_orig != SCHED_CAPACITY_SCALE)
-		fits = fits && (uclamp_min <= capacity_orig_thermal);
+	if (fits && (util < uclamp_min) && (uclamp_min > capacity_orig_thermal))
+		return -1;
 
 	return fits;
 }
@@ -4572,7 +4572,11 @@ static inline int task_fits_cpu(struct task_struct *p, int cpu)
 	unsigned long uclamp_min = uclamp_eff_value(p, UCLAMP_MIN);
 	unsigned long uclamp_max = uclamp_eff_value(p, UCLAMP_MAX);
 	unsigned long util = task_util_est(p);
-	return util_fits_cpu(util, uclamp_min, uclamp_max, cpu);
+	/*
+	 * Return true only if the cpu fully fits the task requirements, which
+	 * include the utilization but also the performance hints.
+	 */
+	return (util_fits_cpu(util, uclamp_min, uclamp_max, cpu) > 0);
 }
 
 static inline void update_misfit_status(struct task_struct *p, struct rq *rq)
@@ -6138,6 +6142,7 @@ static inline bool cpu_overutilized(int cpu)
 	unsigned long rq_util_min = uclamp_rq_get(cpu_rq(cpu), UCLAMP_MIN);
 	unsigned long rq_util_max = uclamp_rq_get(cpu_rq(cpu), UCLAMP_MAX);
 
+	/* Return true only if the utilization doesn't fit CPU's capacity */
 	return !util_fits_cpu(cpu_util_cfs(cpu), rq_util_min, rq_util_max, cpu);
 }
 
@@ -6931,6 +6936,7 @@ static int
 select_idle_capacity(struct task_struct *p, struct sched_domain *sd, int target)
 {
 	unsigned long task_util, util_min, util_max, best_cap = 0;
+	int fits, best_fits = 0;
 	int cpu, best_cpu = -1;
 	struct cpumask *cpus;
 
@@ -6946,12 +6952,28 @@ select_idle_capacity(struct task_struct *p, struct sched_domain *sd, int target)
 
 		if (!available_idle_cpu(cpu) && !sched_idle_cpu(cpu))
 			continue;
-		if (util_fits_cpu(task_util, util_min, util_max, cpu))
+
+		fits = util_fits_cpu(task_util, util_min, util_max, cpu);
+
+		/* This CPU fits with all requirements */
+		if (fits > 0)
 			return cpu;
+		/*
+		 * Only the min performance hint (i.e. uclamp_min) doesn't fit.
+		 * Look for the CPU with best capacity.
+		 */
+		else if (fits < 0)
+			cpu_cap = capacity_orig_of(cpu) - thermal_load_avg(cpu_rq(cpu));
 
-		if (cpu_cap > best_cap) {
+		/*
+		 * First, select CPU which fits better (-1 being better than 0).
+		 * Then, select the one with best capacity at same level.
+		 */
+		if ((fits < best_fits) ||
+		    ((fits == best_fits) && (cpu_cap > best_cap))) {
 			best_cap = cpu_cap;
 			best_cpu = cpu;
+			best_fits = fits;
 		}
 	}
 
@@ -6964,7 +6986,11 @@ static inline bool asym_fits_cpu(unsigned long util,
 				 int cpu)
 {
 	if (sched_asym_cpucap_active())
-		return util_fits_cpu(util, util_min, util_max, cpu);
+		/*
+		 * Return true only if the cpu fully fits the task requirements
+		 * which include the utilization and the performance hints.
+		 */
+		return (util_fits_cpu(util, util_min, util_max, cpu) > 0);
 
 	return true;
 }
@@ -7331,6 +7357,9 @@ static int find_energy_efficient_cpu(struct task_struct *p, int prev_cpu)
 	unsigned long p_util_max = uclamp_is_used() ? uclamp_eff_value(p, UCLAMP_MAX) : 1024;
 	struct root_domain *rd = this_rq()->rd;
 	int cpu, best_energy_cpu, target = -1;
+	int prev_fits = -1, best_fits = -1;
+	unsigned long best_thermal_cap = 0;
+	unsigned long prev_thermal_cap = 0;
 	struct sched_domain *sd;
 	struct perf_domain *pd;
 	struct energy_env eenv;
@@ -7366,6 +7395,7 @@ static int find_energy_efficient_cpu(struct task_struct *p, int prev_cpu)
 		unsigned long prev_spare_cap = 0;
 		int max_spare_cap_cpu = -1;
 		unsigned long base_energy;
+		int fits, max_fits = -1;
 
 		cpumask_and(cpus, perf_domain_span(pd), cpu_online_mask);
 
@@ -7415,7 +7445,9 @@ static int find_energy_efficient_cpu(struct task_struct *p, int prev_cpu)
 				util_min = max(rq_util_min, p_util_min);
 				util_max = max(rq_util_max, p_util_max);
 			}
-			if (!util_fits_cpu(util, util_min, util_max, cpu))
+
+			fits = util_fits_cpu(util, util_min, util_max, cpu);
+			if (!fits)
 				continue;
 
 			lsub_positive(&cpu_cap, util);
@@ -7423,7 +7455,9 @@ static int find_energy_efficient_cpu(struct task_struct *p, int prev_cpu)
 			if (cpu == prev_cpu) {
 				/* Always use prev_cpu as a candidate. */
 				prev_spare_cap = cpu_cap;
-			} else if (cpu_cap > max_spare_cap) {
+				prev_fits = fits;
+			} else if ((fits > max_fits) ||
+				   ((fits == max_fits) && (cpu_cap > max_spare_cap))) {
 				/*
 				 * Find the CPU with the maximum spare capacity
 				 * among the remaining CPUs in the performance
@@ -7431,6 +7465,7 @@ static int find_energy_efficient_cpu(struct task_struct *p, int prev_cpu)
 				 */
 				max_spare_cap = cpu_cap;
 				max_spare_cap_cpu = cpu;
+				max_fits = fits;
 			}
 		}
 
@@ -7449,26 +7484,50 @@ static int find_energy_efficient_cpu(struct task_struct *p, int prev_cpu)
 			if (prev_delta < base_energy)
 				goto unlock;
 			prev_delta -= base_energy;
+			prev_thermal_cap = cpu_thermal_cap;
 			best_delta = min(best_delta, prev_delta);
 		}
 
 		/* Evaluate the energy impact of using max_spare_cap_cpu. */
 		if (max_spare_cap_cpu >= 0 && max_spare_cap > prev_spare_cap) {
+			/* Current best energy cpu fits better */
+			if (max_fits < best_fits)
+				continue;
+
+			/*
+			 * Both don't fit performance hint (i.e. uclamp_min)
+			 * but best energy cpu has better capacity.
+			 */
+			if ((max_fits < 0) &&
+			    (cpu_thermal_cap <= best_thermal_cap))
+				continue;
+
 			cur_delta = compute_energy(&eenv, pd, cpus, p,
 						   max_spare_cap_cpu);
 			/* CPU utilization has changed */
 			if (cur_delta < base_energy)
 				goto unlock;
 			cur_delta -= base_energy;
-			if (cur_delta < best_delta) {
-				best_delta = cur_delta;
-				best_energy_cpu = max_spare_cap_cpu;
-			}
+
+			/*
+			 * Both fit for the task but best energy cpu has lower
+			 * energy impact.
+			 */
+			if ((max_fits > 0) && (best_fits > 0) &&
+			    (cur_delta >= best_delta))
+				continue;
+
+			best_delta = cur_delta;
+			best_energy_cpu = max_spare_cap_cpu;
+			best_fits = max_fits;
+			best_thermal_cap = cpu_thermal_cap;
 		}
 	}
 	rcu_read_unlock();
 
-	if (best_delta < prev_delta)
+	if ((best_fits > prev_fits) ||
+	    ((best_fits > 0) && (best_delta < prev_delta)) ||
+	    ((best_fits < 0) && (best_thermal_cap > prev_thermal_cap)))
 		target = best_energy_cpu;
 
 	return target;
@@ -10271,24 +10330,23 @@ static struct sched_group *find_busiest_group(struct lb_env *env)
 	 */
 	update_sd_lb_stats(env, &sds);
 
-	if (sched_energy_enabled()) {
-		struct root_domain *rd = env->dst_rq->rd;
-
-		if (rcu_dereference(rd->pd) && !READ_ONCE(rd->overutilized))
-			goto out_balanced;
-	}
-
-	local = &sds.local_stat;
-	busiest = &sds.busiest_stat;
-
 	/* There is no busy sibling group to pull tasks from */
 	if (!sds.busiest)
 		goto out_balanced;
 
+	busiest = &sds.busiest_stat;
+
 	/* Misfit tasks should be dealt with regardless of the avg load */
 	if (busiest->group_type == group_misfit_task)
 		goto force_balance;
 
+	if (sched_energy_enabled()) {
+		struct root_domain *rd = env->dst_rq->rd;
+
+		if (rcu_dereference(rd->pd) && !READ_ONCE(rd->overutilized))
+			goto out_balanced;
+	}
+
 	/* ASYM feature bypasses nice load balance check */
 	if (busiest->group_type == group_asym_packing)
 		goto force_balance;
@@ -10301,6 +10359,7 @@ static struct sched_group *find_busiest_group(struct lb_env *env)
 	if (busiest->group_type == group_imbalanced)
 		goto force_balance;
 
+	local = &sds.local_stat;
 	/*
 	 * If the local group is busier than the selected busiest group
 	 * don't try and pull any tasks.