This is a note to let you know that I've just added the patch titled
sched/fair: Remove capacity inversion detection
to the 6.1-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
sched-fair-remove-capacity-inversion-detection.patch
and it can be found in the queue-6.1 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From a2e90611b9f425adbbfcdaa5b5e49958ddf6f61b Mon Sep 17 00:00:00 2001
From: Vincent Guittot <vincent.guittot@xxxxxxxxxx>
Date: Wed, 1 Feb 2023 15:36:28 +0100
Subject: sched/fair: Remove capacity inversion detection
From: Vincent Guittot <vincent.guittot@xxxxxxxxxx>
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@xxxxxxxxxx>
Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
Link: https://lore.kernel.org/r/20230201143628.270912-3-vincent.guittot@xxxxxxxxxx
Signed-off-by: Qais Yousef (Google) <qyousef@xxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
kernel/sched/fair.c | 84 +++------------------------------------------------
kernel/sched/sched.h | 19 -----------
2 files changed, 5 insertions(+), 98 deletions(-)
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -4464,17 +4464,9 @@ static inline int util_fits_cpu(unsigned
*
* 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(i
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;
--- 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_ori
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
Patches currently in stable-queue which might be from vincent.guittot@xxxxxxxxxx are
queue-6.1/sched-fair-remove-capacity-inversion-detection.patch
queue-6.1/sched-fair-unlink-misfit-task-from-cpu-overutilized.patch
