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Date: Wed, 28 Dec 2022 17:54:15 +0100
From: Vincent Guittot <vincent.guittot@...aro.org>
To: mingo@...nel.org, peterz@...radead.org, dietmar.eggemann@....com,
qyousef@...alina.io, rafael@...nel.org, viresh.kumar@...aro.org,
vschneid@...hat.com, linux-pm@...r.kernel.org,
linux-kernel@...r.kernel.org
Cc: lukasz.luba@....com, wvw@...gle.com, xuewen.yan94@...il.com,
han.lin@...iatek.com, Jonathan.JMChen@...iatek.com,
Vincent Guittot <vincent.guittot@...aro.org>
Subject: [PATCH v2] 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 of
may not 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.
Signed-off-by: Vincent Guittot <vincent.guittot@...aro.org>
---
Change since v1:
- fix some wrong conditions
- take into account more cases
kernel/sched/fair.c | 99 +++++++++++++++++++++++++++++++++------------
1 file changed, 74 insertions(+), 25 deletions(-)
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 1649e7d71d24..57077f0a897e 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -4582,8 +4582,7 @@ static inline int util_fits_cpu(unsigned long util,
* 2. The system is being saturated when we're operating near
* max capacity, it doesn't make sense to block overutilized.
*/
- uclamp_max_fits = (capacity_orig == SCHED_CAPACITY_SCALE) && (uclamp_max == SCHED_CAPACITY_SCALE);
- uclamp_max_fits = !uclamp_max_fits && (uclamp_max <= capacity_orig);
+ uclamp_max_fits = (uclamp_max <= capacity_orig) || (capacity_orig == SCHED_CAPACITY_SCALE);
fits = fits || uclamp_max_fits;
/*
@@ -4618,8 +4617,8 @@ 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;
}
@@ -4629,7 +4628,7 @@ 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 (util_fits_cpu(util, uclamp_min, uclamp_max, cpu) > 0);
}
static inline void update_misfit_status(struct task_struct *p, struct rq *rq)
@@ -6864,6 +6863,7 @@ 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;
@@ -6879,12 +6879,28 @@ 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 capacity and performance requirements */
+ if (fits > 0)
return cpu;
+ /*
+ * Only the min performance (i.e. uclamp_min) doesn't fit. Look
+ * for the CPU with highest performance 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 largest 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;
}
}
@@ -6897,7 +6913,7 @@ 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 (util_fits_cpu(util, util_min, util_max, cpu) > 0);
return true;
}
@@ -7264,6 +7280,9 @@ 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;
@@ -7299,6 +7318,7 @@ 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);
@@ -7351,7 +7371,9 @@ static int find_energy_efficient_cpu(struct task_struct *p, int prev_cpu)
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);
@@ -7359,7 +7381,9 @@ 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
@@ -7367,6 +7391,7 @@ 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;
}
}
@@ -7385,26 +7410,50 @@ 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 (i.e. uclamp_min) but
+ * best energy cpu has better performance.
+ */
+ 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) &&
+ (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;
@@ -10228,24 +10277,23 @@ 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;
@@ -10258,6 +10306,7 @@ 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.
--
2.17.1
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