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sched/fair: Merge select_idle_core/cpu() 

Both select_idle_core() and select_idle_cpu() do a loop over the same
cpumask. Observe that by clearing the already visited CPUs, we can
fold the iteration and iterate a core at a time.

All we need to do is remember any non-idle CPU we encountered while
scanning for an idle core. This way we'll only iterate every CPU once.

Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Reviewed-by: Vincent Guittot <vincent.guittot@linaro.org>
Link: https://lkml.kernel.org/r/20210127135203.19633-5-mgorman@techsingularity.net
This commit is contained in:
Mel Gorman 2021-01-27 13:52:03 +00:00 committed by Ingo Molnar
parent 6cd56ef1df
commit 9fe1f127b9
1 changed files with 59 additions and 40 deletions
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81
kernel/sched/fair.c
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@ -6019,6 +6019,14 @@ static inline int find_idlest_cpu(struct sched_domain *sd, struct task_struct *p
return new_cpu;
}
static inline int __select_idle_cpu(int cpu)
{
if (available_idle_cpu(cpu) || sched_idle_cpu(cpu))
return cpu;
return -1;
}
#ifdef CONFIG_SCHED_SMT
DEFINE_STATIC_KEY_FALSE(sched_smt_present);
EXPORT_SYMBOL_GPL(sched_smt_present);
@ -6077,48 +6085,51 @@ void __update_idle_core(struct rq *rq)
* there are no idle cores left in the system; tracked through
* sd_llc->shared->has_idle_cores and enabled through update_idle_core() above.
*/
static int select_idle_core(struct task_struct *p, struct sched_domain *sd, int target)
static int select_idle_core(struct task_struct *p, int core, struct cpumask *cpus, int *idle_cpu)
{
struct cpumask *cpus = this_cpu_cpumask_var_ptr(select_idle_mask);
int core, cpu;
bool idle = true;
int cpu;
if (!static_branch_likely(&sched_smt_present))
return -1;
if (!test_idle_cores(target, false))
return -1;
cpumask_and(cpus, sched_domain_span(sd), p->cpus_ptr);
for_each_cpu_wrap(core, cpus, target) {
bool idle = true;
return __select_idle_cpu(core);
for_each_cpu(cpu, cpu_smt_mask(core)) {
if (!available_idle_cpu(cpu)) {
idle = false;
if (*idle_cpu == -1) {
if (sched_idle_cpu(cpu) && cpumask_test_cpu(cpu, p->cpus_ptr)) {
*idle_cpu = cpu;
break;
}
continue;
}
break;
}
if (*idle_cpu == -1 && cpumask_test_cpu(cpu, p->cpus_ptr))
*idle_cpu = cpu;
}
if (idle)
return core;
cpumask_andnot(cpus, cpus, cpu_smt_mask(core));
}
/*
* Failed to find an idle core; stop looking for one.
*/
set_idle_cores(target, 0);
return -1;
}
#else /* CONFIG_SCHED_SMT */
static inline int select_idle_core(struct task_struct *p, struct sched_domain *sd, int target)
static inline void set_idle_cores(int cpu, int val)
{
return -1;
}
static inline bool test_idle_cores(int cpu, bool def)
{
return def;
}
static inline int select_idle_core(struct task_struct *p, int core, struct cpumask *cpus, int *idle_cpu)
{
return __select_idle_cpu(core);
}
#endif /* CONFIG_SCHED_SMT */
@ -6131,10 +6142,11 @@ static inline int select_idle_core(struct task_struct *p, struct sched_domain *s
static int select_idle_cpu(struct task_struct *p, struct sched_domain *sd, int target)
{
struct cpumask *cpus = this_cpu_cpumask_var_ptr(select_idle_mask);
int i, cpu, idle_cpu = -1, nr = INT_MAX;
bool smt = test_idle_cores(target, false);
int this = smp_processor_id();
struct sched_domain *this_sd;
u64 time;
int this = smp_processor_id();
int cpu, nr = INT_MAX;
this_sd = rcu_dereference(*this_cpu_ptr(&sd_llc));
if (!this_sd)
@ -6142,7 +6154,7 @@ static int select_idle_cpu(struct task_struct *p, struct sched_domain *sd, int t
cpumask_and(cpus, sched_domain_span(sd), p->cpus_ptr);
if (sched_feat(SIS_PROP)) {
if (sched_feat(SIS_PROP) && !smt) {
u64 avg_cost, avg_idle, span_avg;
/*
@ -6162,18 +6174,29 @@ static int select_idle_cpu(struct task_struct *p, struct sched_domain *sd, int t
}
for_each_cpu_wrap(cpu, cpus, target) {
if (smt) {
i = select_idle_core(p, cpu, cpus, &idle_cpu);
if ((unsigned int)i < nr_cpumask_bits)
return i;
} else {
if (!--nr)
return -1;
if (available_idle_cpu(cpu) || sched_idle_cpu(cpu))
idle_cpu = __select_idle_cpu(cpu);
if ((unsigned int)idle_cpu < nr_cpumask_bits)
break;
}
}
if (sched_feat(SIS_PROP)) {
if (smt)
set_idle_cores(this, false);
if (sched_feat(SIS_PROP) && !smt) {
time = cpu_clock(this) - time;
update_avg(&this_sd->avg_scan_cost, time);
}
return cpu;
return idle_cpu;
}
/*
@ -6302,10 +6325,6 @@ static int select_idle_sibling(struct task_struct *p, int prev, int target)
if (!sd)
return target;
i = select_idle_core(p, sd, target);
if ((unsigned)i < nr_cpumask_bits)
return i;
i = select_idle_cpu(p, sd, target);
if ((unsigned)i < nr_cpumask_bits)
return i;