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sched: use the CPU true capacity while sorting the min/mid/max CPUs

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The current code uses the rq->cpu_capacity_orig while sorting
the min/mid/max CPUs while rebuilding the scheduler domains. This
rq->cpu_capacity_orig is subjected to changed when the scaling max
frequency is clipped for that CPU's frequency domain. Since we don't
recompute the min/mid/max CPUs when the capacity is changed, the
sorting becomes incorrect later when the frequency limits are lifted.

The task CPU selection algorithm depends heavily on min/mid/max CPUs
and changing them on the fly results in incorrect task placement.
Hence use the true capacity of CPUs while sorting the min/mid/max
CPUs. This means that the sorting gets changed only when CPUs are
hotplugged out, otherwise these reflect the correct topology
all the time.

The max_cpu_capacity struct in root domain also maintains the
max CPU and its capacity. Since we now use true capacity, there
is no need to compute this on the fly. So move this evaluation from
the periodic load balancer to the scheduler domain rebuilding.

The rq->cpu_capacity_orig is still subjected to change upon frequency
or thermal limits. So we still identify the cases where tasks not
fitting on the max/mid CPUs when the capacity is reduced.

Change-Id: I42735accd079b2ece1eb58d1ebcf322d454e33a2
Signed-off-by: Pavankumar Kondeti <[email protected]>
[[email protected]: trivial changes to arch_scale_cpu_capacity()]
Signed-off-by: Satya Durga Srinivasu Prabhala <[email protected]>
This commit is contained in:
Pavankumar Kondeti 2019-10-14 16:47:10 +05:30 • committed by Gerrit - the friendly Code Review server
commit 408e740773
2 changed files with 20 additions and 32 deletions
Download patch file Download diff file Expand all files Collapse all files

24
kernel/sched/fair.c
View file

@ -8641,10 +8641,6 @@ static void update_cpu_capacity(struct sched_domain *sd, int cpu)
{
unsigned long capacity = arch_scale_cpu_capacity(cpu);
struct sched_group *sdg = sd->groups;
struct max_cpu_capacity *mcc;
unsigned long max_capacity;
int max_cap_cpu;
unsigned long flags;
capacity *= arch_scale_max_freq_capacity(sd, cpu);
capacity >>= SCHED_CAPACITY_SHIFT;
@ -8652,26 +8648,6 @@ static void update_cpu_capacity(struct sched_domain *sd, int cpu)
capacity = min(capacity, thermal_cap(cpu));
cpu_rq(cpu)->cpu_capacity_orig = capacity;
mcc = &cpu_rq(cpu)->rd->max_cpu_capacity;
raw_spin_lock_irqsave(&mcc->lock, flags);
max_capacity = mcc->val;
max_cap_cpu = mcc->cpu;
if ((max_capacity > capacity && max_cap_cpu == cpu) ||
(max_capacity < capacity)) {
mcc->val = capacity;
mcc->cpu = cpu;
#ifdef CONFIG_SCHED_DEBUG
raw_spin_unlock_irqrestore(&mcc->lock, flags);
printk_deferred(KERN_INFO "CPU%d: update max cpu_capacity %lu\n",
cpu, capacity);
goto skip_unlock;
#endif
}
raw_spin_unlock_irqrestore(&mcc->lock, flags);
skip_unlock: __attribute__ ((unused));
capacity = scale_rt_capacity(cpu, capacity);
if (!capacity)

28
kernel/sched/topology.c
View file

@ -2047,12 +2047,12 @@ build_sched_domains(const struct cpumask *cpu_map, struct sched_domain_attr *att
sd = *per_cpu_ptr(d.sd, i);
#ifdef CONFIG_SCHED_WALT
if ((max_cpu < 0) || (cpu_rq(i)->cpu_capacity_orig >
cpu_rq(max_cpu)->cpu_capacity_orig))
if ((max_cpu < 0) || (arch_scale_cpu_capacity(i) >
arch_scale_cpu_capacity(max_cpu)))
WRITE_ONCE(d.rd->max_cap_orig_cpu, i);
if ((min_cpu < 0) || (cpu_rq(i)->cpu_capacity_orig <
cpu_rq(min_cpu)->cpu_capacity_orig))
if ((min_cpu < 0) || (arch_scale_cpu_capacity(i) <
arch_scale_cpu_capacity(min_cpu)))
WRITE_ONCE(d.rd->min_cap_orig_cpu, i);
#endif
@ -2065,15 +2065,27 @@ build_sched_domains(const struct cpumask *cpu_map, struct sched_domain_attr *att
int max_cpu = READ_ONCE(d.rd->max_cap_orig_cpu);
int min_cpu = READ_ONCE(d.rd->min_cap_orig_cpu);
if ((cpu_rq(i)->cpu_capacity_orig
!= cpu_rq(min_cpu)->cpu_capacity_orig) &&
(cpu_rq(i)->cpu_capacity_orig
!= cpu_rq(max_cpu)->cpu_capacity_orig)) {
if ((arch_scale_cpu_capacity(i)
!= arch_scale_cpu_capacity(min_cpu)) &&
(arch_scale_cpu_capacity(i)
!= arch_scale_cpu_capacity(max_cpu))) {
WRITE_ONCE(d.rd->mid_cap_orig_cpu, i);
break;
}
}
/*
* The max_cpu_capacity reflect the original capacity which does not
* change dynamically. So update the max cap CPU and its capacity
* here.
*/
if (d.rd->max_cap_orig_cpu != -1) {
d.rd->max_cpu_capacity.cpu = d.rd->max_cap_orig_cpu;
d.rd->max_cpu_capacity.val = arch_scale_cpu_capacity(
d.rd->max_cap_orig_cpu);
}
#endif
rcu_read_unlock();
if (has_asym)