Decoupling misfit from overutilized better helps handling misfit due to uclamp_min only being misfit without triggering overutilized state, which is bad from energy point of view as it prematurely disables energy aware scheduling.
The series also makes the search for a better CPU under bad thermal condition more comprehensive, which is useful improvement when the system is under bad thermal condition.
Backports to 5.10.y and 5.15.y is hard as find_energy_efficient_cpu() is different. But it applies cleanly on 6.1.y
Compile tested against various randconfigs for different archs.
Boot tested on android14-6.1 GKI kernel.
Based on v6.1.46
Original series
https://lore.kernel.org/lkml/20230201143628.270912-1-vincent.guittot@linaro....
Thanks!
-- Qais Yousef
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(-)
From: Vincent Guittot vincent.guittot@linaro.org
commit e5ed0550c04c5469ecdc1634d8aa18c8609590f0 upstream.
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 (Google) 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 (cherry picked from commit e5ed0550c04c5469ecdc1634d8aa18c8609590f0) Signed-off-by: Qais Yousef (Google) qyousef@layalina.io --- 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 5e5aea2360a8..a45ccee98ab1 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -4549,8 +4549,8 @@ 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; } @@ -4560,7 +4560,11 @@ 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) @@ -6043,6 +6047,7 @@ 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); }
@@ -6836,6 +6841,7 @@ 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;
@@ -6851,12 +6857,28 @@ 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; } }
@@ -6869,7 +6891,11 @@ 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; } @@ -7236,6 +7262,9 @@ 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; @@ -7271,6 +7300,7 @@ 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);
@@ -7320,7 +7350,9 @@ 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); @@ -7328,7 +7360,9 @@ 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 @@ -7336,6 +7370,7 @@ 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; } }
@@ -7354,26 +7389,50 @@ 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; @@ -10183,24 +10242,23 @@ 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; @@ -10213,6 +10271,7 @@ 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.
From: Vincent Guittot vincent.guittot@linaro.org
commit a2e90611b9f425adbbfcdaa5b5e49958ddf6f61b upstream.
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 (cherry picked from commit a2e90611b9f425adbbfcdaa5b5e49958ddf6f61b) Signed-off-by: Qais Yousef (Google) qyousef@layalina.io --- 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 a45ccee98ab1..612873ec2197 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -4464,17 +4464,9 @@ 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. @@ -8929,82 +8921,16 @@ 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 5f18460f62f0..d6d488e8eb55 100644 --- a/kernel/sched/sched.h +++ b/kernel/sched/sched.h @@ -1041,7 +1041,6 @@ struct rq {
unsigned long cpu_capacity; unsigned long cpu_capacity_orig; - unsigned long cpu_capacity_inverted;
struct balance_callback *balance_callback;
@@ -2879,24 +2878,6 @@ 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
On Sun, Aug 20, 2023 at 08:16:48PM +0100, Qais Yousef wrote:
Decoupling misfit from overutilized better helps handling misfit due to uclamp_min only being misfit without triggering overutilized state, which is bad from energy point of view as it prematurely disables energy aware scheduling.
The series also makes the search for a better CPU under bad thermal condition more comprehensive, which is useful improvement when the system is under bad thermal condition.
Backports to 5.10.y and 5.15.y is hard as find_energy_efficient_cpu() is different. But it applies cleanly on 6.1.y
Compile tested against various randconfigs for different archs.
Boot tested on android14-6.1 GKI kernel.
Based on v6.1.46
Original series
https://lore.kernel.org/lkml/20230201143628.270912-1-vincent.guittot@linaro....
Thanks!
Both now queued up, thanks!
greg k-h
linux-stable-mirror@lists.linaro.org
-
Greg KH -
Qais Yousef