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Message-ID: <161356785893.20312.10270833120354178289.tip-bot2@tip-bot2>
Date: Wed, 17 Feb 2021 13:17:38 -0000
From: "tip-bot2 for Mel Gorman" <tip-bot2@...utronix.de>
To: linux-tip-commits@...r.kernel.org
Cc: Mel Gorman <mgorman@...hsingularity.net>,
"Peter Zijlstra (Intel)" <peterz@...radead.org>,
Ingo Molnar <mingo@...nel.org>,
Vincent Guittot <vincent.guittot@...aro.org>, x86@...nel.org,
linux-kernel@...r.kernel.org
Subject: [tip: sched/core] sched/fair: Merge select_idle_core/cpu()
The following commit has been merged into the sched/core branch of tip:
Commit-ID: 9fe1f127b913318c631d0041ecf71486e38c2c2d
Gitweb: https://git.kernel.org/tip/9fe1f127b913318c631d0041ecf71486e38c2c2d
Author: Mel Gorman <mgorman@...hsingularity.net>
AuthorDate: Wed, 27 Jan 2021 13:52:03
Committer: Ingo Molnar <mingo@...nel.org>
CommitterDate: Wed, 17 Feb 2021 14:07:25 +01:00
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@...hsingularity.net>
Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
Signed-off-by: Ingo Molnar <mingo@...nel.org>
Reviewed-by: Vincent Guittot <vincent.guittot@...aro.org>
Link: https://lkml.kernel.org/r/20210127135203.19633-5-mgorman@techsingularity.net
---
kernel/sched/fair.c | 99 +++++++++++++++++++++++++------------------
1 file changed, 59 insertions(+), 40 deletions(-)
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 6a0fc8a..c73d588 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -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 @@ unlock:
* 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);
+ return __select_idle_cpu(core);
- for_each_cpu_wrap(core, cpus, target) {
- bool idle = true;
-
- for_each_cpu(cpu, cpu_smt_mask(core)) {
- if (!available_idle_cpu(cpu)) {
- idle = false;
- break;
+ 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)
- return core;
-
- cpumask_andnot(cpus, cpus, cpu_smt_mask(core));
+ if (*idle_cpu == -1 && cpumask_test_cpu(cpu, p->cpus_ptr))
+ *idle_cpu = cpu;
}
- /*
- * Failed to find an idle core; stop looking for one.
- */
- set_idle_cores(target, 0);
+ if (idle)
+ return core;
+ cpumask_andnot(cpus, cpus, cpu_smt_mask(core));
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 (!--nr)
- return -1;
- if (available_idle_cpu(cpu) || sched_idle_cpu(cpu))
- break;
+ 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;
+ 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;
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