sched/fair: Remove capacity inversion detection

BugLink: https://bugs.launchpad.net/bugs/2039110
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
Signed-off-by: Qais Yousef (Google) <qyousef@layalina.io>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>
Signed-off-by: Stefan Bader <stefan.bader@canonical.com>

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 488b58513655c9d9d981e27fadf8c26e18f0890b..01bae52cafc565f2e372feffd8cbcaddd64fb182 100644 (file)
--- 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.
@@ -8941,82 +8933,16 @@ 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 771f8ddb705337ebfab2bd4fa7ef69b1a59fedae..28ae8ce0ebe328cd0b60f87c70e38c587a5f8ae5 100644 (file)
--- 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;
 
@@ -2893,24 +2892,6 @@ 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