[PATCH v2 00/10] Backport uclamp vs margin fixes into 5.10.y

[PATCH v2 00/10] Backport uclamp vs margin fixes into 5.10.y

[Qais Yousef]

Changes in v2:
	* Fix compilation error against patch 7 due to misiplace #endif to
	  protect against CONFIG_SMP which doesn't contain the newly added
	  field to struct rq.

Commit 2ff401441711 ("sched/uclamp: Fix relationship between uclamp and
migration margin") was cherry-picked into 5.10 kernels but missed the rest of
the series.

This ports the remainder of the fixes.

Based on 5.10.172.

NOTE:

a2e90611b9f4 ("sched/fair: Remove capacity inversion detection") is not
necessary to backport because it has a dependency on e5ed0550c04c ("sched/fair:
unlink misfit task from cpu overutilized") which is nice to have but not
strictly required. It improves the search for best CPU under adverse thermal
pressure to try harder. And the new search effectively replaces the capacity
inversion detection, so it is removed afterwards.

Build tested on (cross compile when necessary; x86_64 otherwise):

	1. default ubuntu config which has uclamp + smp
	2. default ubuntu config without uclamp + smp
	3. default ubunto config without smp (which automatically disables
	   uclamp)
	4. reported riscv-allnoconfig, mips-randconfig, x86_64-randocnfigs

Tested on 5.10 Android GKI kernel and android device (with slight modifications
due to other conflicts on there).

Qais Yousef (10):
  sched/uclamp: Make task_fits_capacity() use util_fits_cpu()
  sched/uclamp: Fix fits_capacity() check in feec()
  sched/uclamp: Make select_idle_capacity() use util_fits_cpu()
  sched/uclamp: Make asym_fits_capacity() use util_fits_cpu()
  sched/uclamp: Make cpu_overutilized() use util_fits_cpu()
  sched/uclamp: Cater for uclamp in find_energy_efficient_cpu()'s early
    exit condition
  sched/fair: Detect capacity inversion
  sched/fair: Consider capacity inversion in util_fits_cpu()
  sched/uclamp: Fix a uninitialized variable warnings
  sched/fair: Fixes for capacity inversion detection

 kernel/sched/core.c  |  10 +--
 kernel/sched/fair.c  | 183 ++++++++++++++++++++++++++++++++++---------
 kernel/sched/sched.h |  70 ++++++++++++++++-
 3 files changed, 217 insertions(+), 46 deletions(-)

-- 
2.25.1

[PATCH v2 01/10] sched/uclamp: Make task_fits_capacity() use util_fits_cpu()

[Qais Yousef]

From: Qais Yousef <qais.yousef@arm.com>

commit b48e16a69792b5dc4a09d6807369d11b2970cc36 upstream.

So that the new uclamp rules in regard to migration margin and capacity
pressure are taken into account correctly.

Fixes: a7008c07a568 ("sched/fair: Make task_fits_capacity() consider uclamp restrictions")
Co-developed-by: Vincent Guittot <vincent.guittot@linaro.org>
Signed-off-by: Qais Yousef <qais.yousef@arm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/r/20220804143609.515789-3-qais.yousef@arm.com
(cherry picked from commit b48e16a69792b5dc4a09d6807369d11b2970cc36)
Signed-off-by: Qais Yousef (Google) <qyousef@layalina.io>
---
 kernel/sched/fair.c  | 26 ++++++++++++++++----------
 kernel/sched/sched.h |  9 +++++++++
 2 files changed, 25 insertions(+), 10 deletions(-)

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index c39d2fc3f994..de7e81cbfed2 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -4197,10 +4197,12 @@ static inline int util_fits_cpu(unsigned long util,
 	return fits;
 }
 
-static inline int task_fits_capacity(struct task_struct *p,
-				     unsigned long capacity)
+static inline int task_fits_cpu(struct task_struct *p, int cpu)
 {
-	return fits_capacity(uclamp_task_util(p), capacity);
+	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);
 }
 
 static inline void update_misfit_status(struct task_struct *p, struct rq *rq)
@@ -4213,7 +4215,7 @@ static inline void update_misfit_status(struct task_struct *p, struct rq *rq)
 		return;
 	}
 
-	if (task_fits_capacity(p, capacity_of(cpu_of(rq)))) {
+	if (task_fits_cpu(p, cpu_of(rq))) {
 		rq->misfit_task_load = 0;
 		return;
 	}
@@ -7898,7 +7900,7 @@ static int detach_tasks(struct lb_env *env)
 
 		case migrate_misfit:
 			/* This is not a misfit task */
-			if (task_fits_capacity(p, capacity_of(env->src_cpu)))
+			if (task_fits_cpu(p, env->src_cpu))
 				goto next;
 
 			env->imbalance = 0;
@@ -8840,6 +8842,10 @@ static inline void update_sg_wakeup_stats(struct sched_domain *sd,
 
 	memset(sgs, 0, sizeof(*sgs));
 
+	/* Assume that task can't fit any CPU of the group */
+	if (sd->flags & SD_ASYM_CPUCAPACITY)
+		sgs->group_misfit_task_load = 1;
+
 	for_each_cpu(i, sched_group_span(group)) {
 		struct rq *rq = cpu_rq(i);
 		unsigned int local;
@@ -8859,12 +8865,12 @@ static inline void update_sg_wakeup_stats(struct sched_domain *sd,
 		if (!nr_running && idle_cpu_without(i, p))
 			sgs->idle_cpus++;
 
-	}
+		/* Check if task fits in the CPU */
+		if (sd->flags & SD_ASYM_CPUCAPACITY &&
+		    sgs->group_misfit_task_load &&
+		    task_fits_cpu(p, i))
+			sgs->group_misfit_task_load = 0;
 
-	/* Check if task fits in the group */
-	if (sd->flags & SD_ASYM_CPUCAPACITY &&
-	    !task_fits_capacity(p, group->sgc->max_capacity)) {
-		sgs->group_misfit_task_load = 1;
 	}
 
 	sgs->group_capacity = group->sgc->capacity;
diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
index 12c65628801c..3758f98c068c 100644
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -2468,6 +2468,15 @@ static inline bool uclamp_is_used(void)
 	return static_branch_likely(&sched_uclamp_used);
 }
 #else /* CONFIG_UCLAMP_TASK */
+static inline unsigned long uclamp_eff_value(struct task_struct *p,
+					     enum uclamp_id clamp_id)
+{
+	if (clamp_id == UCLAMP_MIN)
+		return 0;
+
+	return SCHED_CAPACITY_SCALE;
+}
+
 static inline
 unsigned long uclamp_rq_util_with(struct rq *rq, unsigned long util,
 				  struct task_struct *p)
-- 
2.25.1

[PATCH v2 02/10] sched/uclamp: Fix fits_capacity() check in feec()

[Qais Yousef]

From: Qais Yousef <qais.yousef@arm.com>

commit 244226035a1f9b2b6c326e55ae5188fab4f428cb upstream.

As reported by Yun Hsiang [1], if a task has its uclamp_min >= 0.8 * 1024,
it'll always pick the previous CPU because fits_capacity() will always
return false in this case.

The new util_fits_cpu() logic should handle this correctly for us beside
more corner cases where similar failures could occur, like when using
UCLAMP_MAX.

We open code uclamp_rq_util_with() except for the clamp() part,
util_fits_cpu() needs the 'raw' values to be passed to it.

Also introduce uclamp_rq_{set, get}() shorthand accessors to get uclamp
value for the rq. Makes the code more readable and ensures the right
rules (use READ_ONCE/WRITE_ONCE) are respected transparently.

[1] https://lists.linaro.org/pipermail/eas-dev/2020-July/001488.html

Fixes: 1d42509e475c ("sched/fair: Make EAS wakeup placement consider uclamp restrictions")
Reported-by: Yun Hsiang <hsiang023167@gmail.com>
Signed-off-by: Qais Yousef <qais.yousef@arm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/r/20220804143609.515789-4-qais.yousef@arm.com
(cherry picked from commit 244226035a1f9b2b6c326e55ae5188fab4f428cb)
[Fix trivial conflict in kernel/sched/fair.c due to new automatic
variables in master vs 5.10]
Signed-off-by: Qais Yousef (Google) <qyousef@layalina.io>
---
 kernel/sched/core.c  | 10 +++++-----
 kernel/sched/fair.c  | 26 ++++++++++++++++++++++++--
 kernel/sched/sched.h | 42 +++++++++++++++++++++++++++++++++++++++---
 3 files changed, 68 insertions(+), 10 deletions(-)

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 1303a2607f1f..7c151cf7b7c1 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -980,7 +980,7 @@ static inline void uclamp_idle_reset(struct rq *rq, enum uclamp_id clamp_id,
 	if (!(rq->uclamp_flags & UCLAMP_FLAG_IDLE))
 		return;
 
-	WRITE_ONCE(rq->uclamp[clamp_id].value, clamp_value);
+	uclamp_rq_set(rq, clamp_id, clamp_value);
 }
 
 static inline
@@ -1158,8 +1158,8 @@ static inline void uclamp_rq_inc_id(struct rq *rq, struct task_struct *p,
 	if (bucket->tasks == 1 || uc_se->value > bucket->value)
 		bucket->value = uc_se->value;
 
-	if (uc_se->value > READ_ONCE(uc_rq->value))
-		WRITE_ONCE(uc_rq->value, uc_se->value);
+	if (uc_se->value > uclamp_rq_get(rq, clamp_id))
+		uclamp_rq_set(rq, clamp_id, uc_se->value);
 }
 
 /*
@@ -1225,7 +1225,7 @@ static inline void uclamp_rq_dec_id(struct rq *rq, struct task_struct *p,
 	if (likely(bucket->tasks))
 		return;
 
-	rq_clamp = READ_ONCE(uc_rq->value);
+	rq_clamp = uclamp_rq_get(rq, clamp_id);
 	/*
 	 * Defensive programming: this should never happen. If it happens,
 	 * e.g. due to future modification, warn and fixup the expected value.
@@ -1233,7 +1233,7 @@ static inline void uclamp_rq_dec_id(struct rq *rq, struct task_struct *p,
 	SCHED_WARN_ON(bucket->value > rq_clamp);
 	if (bucket->value >= rq_clamp) {
 		bkt_clamp = uclamp_rq_max_value(rq, clamp_id, uc_se->value);
-		WRITE_ONCE(uc_rq->value, bkt_clamp);
+		uclamp_rq_set(rq, clamp_id, bkt_clamp);
 	}
 }
 
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index de7e81cbfed2..642869018e42 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -6755,6 +6755,8 @@ compute_energy(struct task_struct *p, int dst_cpu, struct perf_domain *pd)
 static int find_energy_efficient_cpu(struct task_struct *p, int prev_cpu)
 {
 	unsigned long prev_delta = ULONG_MAX, best_delta = ULONG_MAX;
+	unsigned long p_util_min = uclamp_is_used() ? uclamp_eff_value(p, UCLAMP_MIN) : 0;
+	unsigned long p_util_max = uclamp_is_used() ? uclamp_eff_value(p, UCLAMP_MAX) : 1024;
 	struct root_domain *rd = cpu_rq(smp_processor_id())->rd;
 	unsigned long cpu_cap, util, base_energy = 0;
 	int cpu, best_energy_cpu = prev_cpu;
@@ -6782,6 +6784,8 @@ static int find_energy_efficient_cpu(struct task_struct *p, int prev_cpu)
 
 	for (; pd; pd = pd->next) {
 		unsigned long cur_delta, spare_cap, max_spare_cap = 0;
+		unsigned long rq_util_min, rq_util_max;
+		unsigned long util_min, util_max;
 		unsigned long base_energy_pd;
 		int max_spare_cap_cpu = -1;
 
@@ -6805,8 +6809,26 @@ static int find_energy_efficient_cpu(struct task_struct *p, int prev_cpu)
 			 * much capacity we can get out of the CPU; this is
 			 * aligned with schedutil_cpu_util().
 			 */
-			util = uclamp_rq_util_with(cpu_rq(cpu), util, p);
-			if (!fits_capacity(util, cpu_cap))
+			if (uclamp_is_used()) {
+				if (uclamp_rq_is_idle(cpu_rq(cpu))) {
+					util_min = p_util_min;
+					util_max = p_util_max;
+				} else {
+					/*
+					 * Open code uclamp_rq_util_with() except for
+					 * the clamp() part. Ie: apply max aggregation
+					 * only. util_fits_cpu() logic requires to
+					 * operate on non clamped util but must use the
+					 * max-aggregated uclamp_{min, max}.
+					 */
+					rq_util_min = uclamp_rq_get(cpu_rq(cpu), UCLAMP_MIN);
+					rq_util_max = uclamp_rq_get(cpu_rq(cpu), UCLAMP_MAX);
+
+					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))
 				continue;
 
 			/* Always use prev_cpu as a candidate. */
diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
index 3758f98c068c..d4632e50d8b3 100644
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -2402,6 +2402,23 @@ static inline void cpufreq_update_util(struct rq *rq, unsigned int flags) {}
 #ifdef CONFIG_UCLAMP_TASK
 unsigned long uclamp_eff_value(struct task_struct *p, enum uclamp_id clamp_id);
 
+static inline unsigned long uclamp_rq_get(struct rq *rq,
+					  enum uclamp_id clamp_id)
+{
+	return READ_ONCE(rq->uclamp[clamp_id].value);
+}
+
+static inline void uclamp_rq_set(struct rq *rq, enum uclamp_id clamp_id,
+				 unsigned int value)
+{
+	WRITE_ONCE(rq->uclamp[clamp_id].value, value);
+}
+
+static inline bool uclamp_rq_is_idle(struct rq *rq)
+{
+	return rq->uclamp_flags & UCLAMP_FLAG_IDLE;
+}
+
 /**
  * uclamp_rq_util_with - clamp @util with @rq and @p effective uclamp values.
  * @rq:		The rq to clamp against. Must not be NULL.
@@ -2437,12 +2454,12 @@ unsigned long uclamp_rq_util_with(struct rq *rq, unsigned long util,
 		 * Ignore last runnable task's max clamp, as this task will
 		 * reset it. Similarly, no need to read the rq's min clamp.
 		 */
-		if (rq->uclamp_flags & UCLAMP_FLAG_IDLE)
+		if (uclamp_rq_is_idle(rq))
 			goto out;
 	}
 
-	min_util = max_t(unsigned long, min_util, READ_ONCE(rq->uclamp[UCLAMP_MIN].value));
-	max_util = max_t(unsigned long, max_util, READ_ONCE(rq->uclamp[UCLAMP_MAX].value));
+	min_util = max_t(unsigned long, min_util, uclamp_rq_get(rq, UCLAMP_MIN));
+	max_util = max_t(unsigned long, max_util, uclamp_rq_get(rq, UCLAMP_MAX));
 out:
 	/*
 	 * Since CPU's {min,max}_util clamps are MAX aggregated considering
@@ -2488,6 +2505,25 @@ static inline bool uclamp_is_used(void)
 {
 	return false;
 }
+
+static inline unsigned long uclamp_rq_get(struct rq *rq,
+					  enum uclamp_id clamp_id)
+{
+	if (clamp_id == UCLAMP_MIN)
+		return 0;
+
+	return SCHED_CAPACITY_SCALE;
+}
+
+static inline void uclamp_rq_set(struct rq *rq, enum uclamp_id clamp_id,
+				 unsigned int value)
+{
+}
+
+static inline bool uclamp_rq_is_idle(struct rq *rq)
+{
+	return false;
+}
 #endif /* CONFIG_UCLAMP_TASK */
 
 #ifdef arch_scale_freq_capacity
-- 
2.25.1

[PATCH v2 03/10] sched/uclamp: Make select_idle_capacity() use util_fits_cpu()

[Qais Yousef]

From: Qais Yousef <qais.yousef@arm.com>

commit b759caa1d9f667b94727b2ad12589cbc4ce13a82 upstream.

Use the new util_fits_cpu() to ensure migration margin and capacity
pressure are taken into account correctly when uclamp is being used
otherwise we will fail to consider CPUs as fitting in scenarios where
they should.

Fixes: b4c9c9f15649 ("sched/fair: Prefer prev cpu in asymmetric wakeup path")
Signed-off-by: Qais Yousef <qais.yousef@arm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/r/20220804143609.515789-5-qais.yousef@arm.com
(cherry picked from commit b759caa1d9f667b94727b2ad12589cbc4ce13a82)
Signed-off-by: Qais Yousef (Google) <qyousef@layalina.io>
---
 kernel/sched/fair.c | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 642869018e42..efbd1cdce508 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -6347,21 +6347,23 @@ static int select_idle_cpu(struct task_struct *p, struct sched_domain *sd, int t
 static int
 select_idle_capacity(struct task_struct *p, struct sched_domain *sd, int target)
 {
-	unsigned long task_util, best_cap = 0;
+	unsigned long task_util, util_min, util_max, best_cap = 0;
 	int cpu, best_cpu = -1;
 	struct cpumask *cpus;
 
 	cpus = this_cpu_cpumask_var_ptr(select_idle_mask);
 	cpumask_and(cpus, sched_domain_span(sd), p->cpus_ptr);
 
-	task_util = uclamp_task_util(p);
+	task_util = task_util_est(p);
+	util_min = uclamp_eff_value(p, UCLAMP_MIN);
+	util_max = uclamp_eff_value(p, UCLAMP_MAX);
 
 	for_each_cpu_wrap(cpu, cpus, target) {
 		unsigned long cpu_cap = capacity_of(cpu);
 
 		if (!available_idle_cpu(cpu) && !sched_idle_cpu(cpu))
 			continue;
-		if (fits_capacity(task_util, cpu_cap))
+		if (util_fits_cpu(task_util, util_min, util_max, cpu))
 			return cpu;
 
 		if (cpu_cap > best_cap) {
-- 
2.25.1

[PATCH v2 04/10] sched/uclamp: Make asym_fits_capacity() use util_fits_cpu()

[Qais Yousef]

From: Qais Yousef <qais.yousef@arm.com>

commit a2e7f03ed28fce26c78b985f87913b6ce3accf9d upstream.

Use the new util_fits_cpu() to ensure migration margin and capacity
pressure are taken into account correctly when uclamp is being used
otherwise we will fail to consider CPUs as fitting in scenarios where
they should.

s/asym_fits_capacity/asym_fits_cpu/ to better reflect what it does now.

Fixes: b4c9c9f15649 ("sched/fair: Prefer prev cpu in asymmetric wakeup path")
Signed-off-by: Qais Yousef <qais.yousef@arm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/r/20220804143609.515789-6-qais.yousef@arm.com
(cherry picked from commit a2e7f03ed28fce26c78b985f87913b6ce3accf9d)
[Conflict in kernel/sched/fair.c due different name of static key
wrapper function and slightly different if condition block in one of the
asym_fits_cpu() call sites]
Signed-off-by: Qais Yousef (Google) <qyousef@layalina.io>
---
 kernel/sched/fair.c | 21 +++++++++++++--------
 1 file changed, 13 insertions(+), 8 deletions(-)

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index efbd1cdce508..b03633bc994f 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -6375,10 +6375,13 @@ select_idle_capacity(struct task_struct *p, struct sched_domain *sd, int target)
 	return best_cpu;
 }
 
-static inline bool asym_fits_capacity(unsigned long task_util, int cpu)
+static inline bool asym_fits_cpu(unsigned long util,
+				 unsigned long util_min,
+				 unsigned long util_max,
+				 int cpu)
 {
 	if (static_branch_unlikely(&sched_asym_cpucapacity))
-		return fits_capacity(task_util, capacity_of(cpu));
+		return util_fits_cpu(util, util_min, util_max, cpu);
 
 	return true;
 }
@@ -6389,7 +6392,7 @@ static inline bool asym_fits_capacity(unsigned long task_util, int cpu)
 static int select_idle_sibling(struct task_struct *p, int prev, int target)
 {
 	struct sched_domain *sd;
-	unsigned long task_util;
+	unsigned long task_util, util_min, util_max;
 	int i, recent_used_cpu;
 
 	/*
@@ -6398,11 +6401,13 @@ static int select_idle_sibling(struct task_struct *p, int prev, int target)
 	 */
 	if (static_branch_unlikely(&sched_asym_cpucapacity)) {
 		sync_entity_load_avg(&p->se);
-		task_util = uclamp_task_util(p);
+		task_util = task_util_est(p);
+		util_min = uclamp_eff_value(p, UCLAMP_MIN);
+		util_max = uclamp_eff_value(p, UCLAMP_MAX);
 	}
 
 	if ((available_idle_cpu(target) || sched_idle_cpu(target)) &&
-	    asym_fits_capacity(task_util, target))
+	    asym_fits_cpu(task_util, util_min, util_max, target))
 		return target;
 
 	/*
@@ -6410,7 +6415,7 @@ static int select_idle_sibling(struct task_struct *p, int prev, int target)
 	 */
 	if (prev != target && cpus_share_cache(prev, target) &&
 	    (available_idle_cpu(prev) || sched_idle_cpu(prev)) &&
-	    asym_fits_capacity(task_util, prev))
+	    asym_fits_cpu(task_util, util_min, util_max, prev))
 		return prev;
 
 	/*
@@ -6425,7 +6430,7 @@ static int select_idle_sibling(struct task_struct *p, int prev, int target)
 	    in_task() &&
 	    prev == smp_processor_id() &&
 	    this_rq()->nr_running <= 1 &&
-	    asym_fits_capacity(task_util, prev)) {
+	    asym_fits_cpu(task_util, util_min, util_max, prev)) {
 		return prev;
 	}
 
@@ -6436,7 +6441,7 @@ static int select_idle_sibling(struct task_struct *p, int prev, int target)
 	    cpus_share_cache(recent_used_cpu, target) &&
 	    (available_idle_cpu(recent_used_cpu) || sched_idle_cpu(recent_used_cpu)) &&
 	    cpumask_test_cpu(p->recent_used_cpu, p->cpus_ptr) &&
-	    asym_fits_capacity(task_util, recent_used_cpu)) {
+	    asym_fits_cpu(task_util, util_min, util_max, recent_used_cpu)) {
 		/*
 		 * Replace recent_used_cpu with prev as it is a potential
 		 * candidate for the next wake:
-- 
2.25.1

[PATCH v2 05/10] sched/uclamp: Make cpu_overutilized() use util_fits_cpu()

[Qais Yousef]

From: Qais Yousef <qais.yousef@arm.com>

commit c56ab1b3506ba0e7a872509964b100912bde165d upstream.

So that it is now uclamp aware.

This fixes a major problem of busy tasks capped with UCLAMP_MAX keeping
the system in overutilized state which disables EAS and leads to wasting
energy in the long run.

Without this patch running a busy background activity like JIT
compilation on Pixel 6 causes the system to be in overutilized state
74.5% of the time.

With this patch this goes down to  9.79%.

It also fixes another problem when long running tasks that have their
UCLAMP_MIN changed while running such that they need to upmigrate to
honour the new UCLAMP_MIN value. The upmigration doesn't get triggered
because overutilized state never gets set in this state, hence misfit
migration never happens at tick in this case until the task wakes up
again.

Fixes: af24bde8df202 ("sched/uclamp: Add uclamp support to energy_compute()")
Signed-off-by: Qais Yousef <qais.yousef@arm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/r/20220804143609.515789-7-qais.yousef@arm.com
(cherry picked from commit c56ab1b3506ba0e7a872509964b100912bde165d)
[Conflict in kernel/sched/fair.c: use cpu_util() instead of
cpu_util_cfs()]
Signed-off-by: Qais Yousef (Google) <qyousef@layalina.io>
---
 kernel/sched/fair.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index b03633bc994f..fdfbed1e9be5 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -5610,7 +5610,10 @@ static inline unsigned long cpu_util(int cpu);
 
 static inline bool cpu_overutilized(int cpu)
 {
-	return !fits_capacity(cpu_util(cpu), capacity_of(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 !util_fits_cpu(cpu_util(cpu), rq_util_min, rq_util_max, cpu);
 }
 
 static inline void update_overutilized_status(struct rq *rq)
-- 
2.25.1

[PATCH v2 06/10] sched/uclamp: Cater for uclamp in find_energy_efficient_cpu()'s early exit condition

[Qais Yousef]

From: Qais Yousef <qais.yousef@arm.com>

commit d81304bc6193554014d4372a01debdf65e1e9a4d upstream.

If the utilization of the woken up task is 0, we skip the energy
calculation because it has no impact.

But if the task is boosted (uclamp_min != 0) will have an impact on task
placement and frequency selection. Only skip if the util is truly
0 after applying uclamp values.

Change uclamp_task_cpu() signature to avoid unnecessary additional calls
to uclamp_eff_get(). feec() is the only user now.

Fixes: 732cd75b8c920 ("sched/fair: Select an energy-efficient CPU on task wake-up")
Signed-off-by: Qais Yousef <qais.yousef@arm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/r/20220804143609.515789-8-qais.yousef@arm.com
(cherry picked from commit d81304bc6193554014d4372a01debdf65e1e9a4d)
Signed-off-by: Qais Yousef (Google) <qyousef@layalina.io>
---
 kernel/sched/fair.c | 14 ++++++++------
 1 file changed, 8 insertions(+), 6 deletions(-)

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index fdfbed1e9be5..d25c6122e243 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -3928,14 +3928,16 @@ static inline unsigned long task_util_est(struct task_struct *p)
 }
 
 #ifdef CONFIG_UCLAMP_TASK
-static inline unsigned long uclamp_task_util(struct task_struct *p)
+static inline unsigned long uclamp_task_util(struct task_struct *p,
+					     unsigned long uclamp_min,
+					     unsigned long uclamp_max)
 {
-	return clamp(task_util_est(p),
-		     uclamp_eff_value(p, UCLAMP_MIN),
-		     uclamp_eff_value(p, UCLAMP_MAX));
+	return clamp(task_util_est(p), uclamp_min, uclamp_max);
 }
 #else
-static inline unsigned long uclamp_task_util(struct task_struct *p)
+static inline unsigned long uclamp_task_util(struct task_struct *p,
+					     unsigned long uclamp_min,
+					     unsigned long uclamp_max)
 {
 	return task_util_est(p);
 }
@@ -6789,7 +6791,7 @@ static int find_energy_efficient_cpu(struct task_struct *p, int prev_cpu)
 		goto fail;
 
 	sync_entity_load_avg(&p->se);
-	if (!task_util_est(p))
+	if (!uclamp_task_util(p, p_util_min, p_util_max))
 		goto unlock;
 
 	for (; pd; pd = pd->next) {
-- 
2.25.1

[PATCH v2 07/10] sched/fair: Detect capacity inversion

[Qais Yousef]

From: Qais Yousef <qais.yousef@arm.com>

commit: 44c7b80bffc3a657a36857098d5d9c49d94e652b upstream.

Check each performance domain to see if thermal pressure is causing its
capacity to be lower than another performance domain.

We assume that each performance domain has CPUs with the same
capacities, which is similar to an assumption made in energy_model.c

We also assume that thermal pressure impacts all CPUs in a performance
domain equally.

If there're multiple performance domains with the same capacity_orig, we
will trigger a capacity inversion if the domain is under thermal
pressure.

The new cpu_in_capacity_inversion() should help users to know when
information about capacity_orig are not reliable and can opt in to use
the inverted capacity as the 'actual' capacity_orig.

Signed-off-by: Qais Yousef <qais.yousef@arm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/r/20220804143609.515789-9-qais.yousef@arm.com
(cherry picked from commit 44c7b80bffc3a657a36857098d5d9c49d94e652b)
[Trivial conflict in kernel/sched/fair.c and sched.h due to code shuffling]
Signed-off-by: Qais Yousef (Google) <qyousef@layalina.io>
---
 kernel/sched/fair.c  | 63 +++++++++++++++++++++++++++++++++++++++++---
 kernel/sched/sched.h | 19 +++++++++++++
 2 files changed, 79 insertions(+), 3 deletions(-)

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index d25c6122e243..b22f6e80ed62 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -8332,16 +8332,73 @@ 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);
 
-	cpu_rq(cpu)->cpu_capacity_orig = arch_scale_cpu_capacity(cpu);
+	rq->cpu_capacity_orig = capacity_orig;
 
 	if (!capacity)
 		capacity = 1;
 
-	cpu_rq(cpu)->cpu_capacity = capacity;
-	trace_sched_cpu_capacity_tp(cpu_rq(cpu));
+	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 (static_branch_unlikely(&sched_asym_cpucapacity)) {
+		unsigned long inv_cap = capacity_orig - thermal_load_avg(rq);
+		struct perf_domain *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;
+
+			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;
+			}
+		}
+	}
+
+	trace_sched_cpu_capacity_tp(rq);
 
 	sdg->sgc->capacity = capacity;
 	sdg->sgc->min_capacity = capacity;
diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
index d4632e50d8b3..852e856eed48 100644
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -973,6 +973,7 @@ struct rq {
 
 	unsigned long		cpu_capacity;
 	unsigned long		cpu_capacity_orig;
+	unsigned long		cpu_capacity_inverted;
 
 	struct callback_head	*balance_callback;
 
@@ -2539,6 +2540,24 @@ 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;
+}
 #endif
 
 /**
-- 
2.25.1

[PATCH v2 08/10] sched/fair: Consider capacity inversion in util_fits_cpu()

[Qais Yousef]

From: Qais Yousef <qais.yousef@arm.com>

commit: aa69c36f31aadc1669bfa8a3de6a47b5e6c98ee8 upstream.

We do consider thermal pressure in util_fits_cpu() for uclamp_min only.
With the exception of the biggest cores which by definition are the max
performance point of the system and all tasks by definition should fit.

Even under thermal pressure, the capacity of the biggest CPU is the
highest in the system and should still fit every task. Except when it
reaches capacity inversion point, then this is no longer true.

We can handle this by using the inverted capacity as capacity_orig in
util_fits_cpu(). Which not only addresses the problem above, but also
ensure uclamp_max now considers the inverted capacity. Force fitting
a task when a CPU is in this adverse state will contribute to making the
thermal throttling last longer.

Signed-off-by: Qais Yousef <qais.yousef@arm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/r/20220804143609.515789-10-qais.yousef@arm.com
(cherry picked from commit aa69c36f31aadc1669bfa8a3de6a47b5e6c98ee8)
Signed-off-by: Qais Yousef (Google) <qyousef@layalina.io>
---
 kernel/sched/fair.c | 14 +++++++++-----
 1 file changed, 9 insertions(+), 5 deletions(-)

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index b22f6e80ed62..67db24a7a5f8 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -4113,12 +4113,16 @@ 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.
+	 * In case of capacity inversion 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);
+	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);
+	}
 
 	/*
 	 * We want to force a task to fit a cpu as implied by uclamp_max.
-- 
2.25.1

[PATCH v2 09/10] sched/uclamp: Fix a uninitialized variable warnings

[Qais Yousef]

commit e26fd28db82899be71b4b949527373d0a6be1e65 upstream.

Addresses the following warnings:

> config: riscv-randconfig-m031-20221111
> compiler: riscv64-linux-gcc (GCC) 12.1.0
>
> smatch warnings:
> kernel/sched/fair.c:7263 find_energy_efficient_cpu() error: uninitialized symbol 'util_min'.
> kernel/sched/fair.c:7263 find_energy_efficient_cpu() error: uninitialized symbol 'util_max'.

Fixes: 244226035a1f ("sched/uclamp: Fix fits_capacity() check in feec()")
Reported-by: kernel test robot <lkp@intel.com>
Reported-by: Dan Carpenter <error27@gmail.com>
Signed-off-by: Qais Yousef (Google) <qyousef@layalina.io>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Vincent Guittot <vincent.guittot@linaro.org>
Link: https://lore.kernel.org/r/20230112122708.330667-2-qyousef@layalina.io
(cherry picked from commit e26fd28db82899be71b4b949527373d0a6be1e65)
[Conflict in kernel/sched/fair.c due to new automatic variable in
master vs 5.10 and new code around for loop]
Signed-off-by: Qais Yousef (Google) <qyousef@layalina.io>
---
 kernel/sched/fair.c | 35 ++++++++++++++++-------------------
 1 file changed, 16 insertions(+), 19 deletions(-)

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 67db24a7a5f8..e3910f73ad65 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -6799,9 +6799,9 @@ static int find_energy_efficient_cpu(struct task_struct *p, int prev_cpu)
 		goto unlock;
 
 	for (; pd; pd = pd->next) {
+		unsigned long util_min = p_util_min, util_max = p_util_max;
 		unsigned long cur_delta, spare_cap, max_spare_cap = 0;
 		unsigned long rq_util_min, rq_util_max;
-		unsigned long util_min, util_max;
 		unsigned long base_energy_pd;
 		int max_spare_cap_cpu = -1;
 
@@ -6810,6 +6810,8 @@ static int find_energy_efficient_cpu(struct task_struct *p, int prev_cpu)
 		base_energy += base_energy_pd;
 
 		for_each_cpu_and(cpu, perf_domain_span(pd), sched_domain_span(sd)) {
+			struct rq *rq = cpu_rq(cpu);
+
 			if (!cpumask_test_cpu(cpu, p->cpus_ptr))
 				continue;
 
@@ -6825,24 +6827,19 @@ static int find_energy_efficient_cpu(struct task_struct *p, int prev_cpu)
 			 * much capacity we can get out of the CPU; this is
 			 * aligned with schedutil_cpu_util().
 			 */
-			if (uclamp_is_used()) {
-				if (uclamp_rq_is_idle(cpu_rq(cpu))) {
-					util_min = p_util_min;
-					util_max = p_util_max;
-				} else {
-					/*
-					 * Open code uclamp_rq_util_with() except for
-					 * the clamp() part. Ie: apply max aggregation
-					 * only. util_fits_cpu() logic requires to
-					 * operate on non clamped util but must use the
-					 * max-aggregated uclamp_{min, max}.
-					 */
-					rq_util_min = uclamp_rq_get(cpu_rq(cpu), UCLAMP_MIN);
-					rq_util_max = uclamp_rq_get(cpu_rq(cpu), UCLAMP_MAX);
-
-					util_min = max(rq_util_min, p_util_min);
-					util_max = max(rq_util_max, p_util_max);
-				}
+			if (uclamp_is_used() && !uclamp_rq_is_idle(rq)) {
+				/*
+				 * Open code uclamp_rq_util_with() except for
+				 * the clamp() part. Ie: apply max aggregation
+				 * only. util_fits_cpu() logic requires to
+				 * operate on non clamped util but must use the
+				 * max-aggregated uclamp_{min, max}.
+				 */
+				rq_util_min = uclamp_rq_get(rq, UCLAMP_MIN);
+				rq_util_max = uclamp_rq_get(rq, UCLAMP_MAX);
+
+				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))
 				continue;
-- 
2.25.1

[PATCH v2 10/10] sched/fair: Fixes for capacity inversion detection

[Qais Yousef]

commit da07d2f9c153e457e845d4dcfdd13568d71d18a4 upstream.

Traversing the Perf Domains requires rcu_read_lock() to be held and is
conditional on sched_energy_enabled(). Ensure right protections applied.

Also skip capacity inversion detection for our own pd; which was an
error.

Fixes: 44c7b80bffc3 ("sched/fair: Detect capacity inversion")
Reported-by: Dietmar Eggemann <dietmar.eggemann@arm.com>
Signed-off-by: Qais Yousef (Google) <qyousef@layalina.io>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Vincent Guittot <vincent.guittot@linaro.org>
Link: https://lore.kernel.org/r/20230112122708.330667-3-qyousef@layalina.io
(cherry picked from commit da07d2f9c153e457e845d4dcfdd13568d71d18a4)
Signed-off-by: Qais Yousef (Google) <qyousef@layalina.io>
---
 kernel/sched/fair.c | 13 +++++++++++--
 1 file changed, 11 insertions(+), 2 deletions(-)

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index e3910f73ad65..b654c25a26cb 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -8363,16 +8363,23 @@ static void update_cpu_capacity(struct sched_domain *sd, int cpu)
 	 *   * Thermal pressure will impact all cpus in this perf domain
 	 *     equally.
 	 */
-	if (static_branch_unlikely(&sched_asym_cpucapacity)) {
+	if (sched_energy_enabled()) {
 		unsigned long inv_cap = capacity_orig - thermal_load_avg(rq);
-		struct perf_domain *pd = rcu_dereference(rq->rd->pd);
+		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);
 
@@ -8397,6 +8404,8 @@ static void update_cpu_capacity(struct sched_domain *sd, int cpu)
 				break;
 			}
 		}
+
+		rcu_read_unlock();
 	}
 
 	trace_sched_cpu_capacity_tp(rq);
-- 
2.25.1

Re: [PATCH v2 00/10] Backport uclamp vs margin fixes into 5.10.y

[Qais Yousef]

Hi

On 03/18/23 17:39, Qais Yousef wrote:
> Changes in v2:
> 	* Fix compilation error against patch 7 due to misiplace #endif to
> 	  protect against CONFIG_SMP which doesn't contain the newly added
> 	  field to struct rq.
> 
> Commit 2ff401441711 ("sched/uclamp: Fix relationship between uclamp and
> migration margin") was cherry-picked into 5.10 kernels but missed the rest of
> the series.
> 
> This ports the remainder of the fixes.
> 
> Based on 5.10.172.
> 
> NOTE:
> 
> a2e90611b9f4 ("sched/fair: Remove capacity inversion detection") is not
> necessary to backport because it has a dependency on e5ed0550c04c ("sched/fair:
> unlink misfit task from cpu overutilized") which is nice to have but not
> strictly required. It improves the search for best CPU under adverse thermal
> pressure to try harder. And the new search effectively replaces the capacity
> inversion detection, so it is removed afterwards.
> 
> Build tested on (cross compile when necessary; x86_64 otherwise):
> 
> 	1. default ubuntu config which has uclamp + smp
> 	2. default ubuntu config without uclamp + smp
> 	3. default ubunto config without smp (which automatically disables
> 	   uclamp)
> 	4. reported riscv-allnoconfig, mips-randconfig, x86_64-randocnfigs
> 
> Tested on 5.10 Android GKI kernel and android device (with slight modifications
> due to other conflicts on there).

Just checking if this has slipped through the cracks or it's on the queue just
waiting for the right time to be picked up. There's a similar backport for 5.15
too.


Thanks!

--
Qais Yousef

Re: [PATCH v2 00/10] Backport uclamp vs margin fixes into 5.10.y

[Greg Kroah-Hartman]

On Tue, Apr 18, 2023 at 02:03:09PM +0100, Qais Yousef wrote:
> Hi
> 
> On 03/18/23 17:39, Qais Yousef wrote:
> > Changes in v2:
> > 	* Fix compilation error against patch 7 due to misiplace #endif to
> > 	  protect against CONFIG_SMP which doesn't contain the newly added
> > 	  field to struct rq.
> > 
> > Commit 2ff401441711 ("sched/uclamp: Fix relationship between uclamp and
> > migration margin") was cherry-picked into 5.10 kernels but missed the rest of
> > the series.
> > 
> > This ports the remainder of the fixes.
> > 
> > Based on 5.10.172.
> > 
> > NOTE:
> > 
> > a2e90611b9f4 ("sched/fair: Remove capacity inversion detection") is not
> > necessary to backport because it has a dependency on e5ed0550c04c ("sched/fair:
> > unlink misfit task from cpu overutilized") which is nice to have but not
> > strictly required. It improves the search for best CPU under adverse thermal
> > pressure to try harder. And the new search effectively replaces the capacity
> > inversion detection, so it is removed afterwards.
> > 
> > Build tested on (cross compile when necessary; x86_64 otherwise):
> > 
> > 	1. default ubuntu config which has uclamp + smp
> > 	2. default ubuntu config without uclamp + smp
> > 	3. default ubunto config without smp (which automatically disables
> > 	   uclamp)
> > 	4. reported riscv-allnoconfig, mips-randconfig, x86_64-randocnfigs
> > 
> > Tested on 5.10 Android GKI kernel and android device (with slight modifications
> > due to other conflicts on there).
> 
> Just checking if this has slipped through the cracks or it's on the queue just
> waiting for the right time to be picked up. There's a similar backport for 5.15
> too.

Did you miss my response a few hours ago:
	https://lore.kernel.org/r/2023041842-treachery-esophagus-7727@gregkh