From: Peter Zijlstra (Intel) <[email protected]>
Instead of calculating how many (logical) CPUs to scan, compute how
many cores to scan.
This changes behaviour for anything !SMT2.
Signed-off-by: Peter Zijlstra (Intel) <[email protected]>
Signed-off-by: Mel Gorman <[email protected]>
---
kernel/sched/core.c | 17 ++++++++++++-----
kernel/sched/fair.c | 11 +++++++++--
kernel/sched/sched.h | 2 ++
3 files changed, 23 insertions(+), 7 deletions(-)
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 2d9ff40f4661..7c073b67f1ea 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -8647,11 +8647,18 @@ int sched_cpu_activate(unsigned int cpu)
balance_push_set(cpu, false);
#ifdef CONFIG_SCHED_SMT
- /*
- * When going up, increment the number of cores with SMT present.
- */
- if (cpumask_weight(cpu_smt_mask(cpu)) == 2)
- static_branch_inc_cpuslocked(&sched_smt_present);
+ do {
+ int weight = cpumask_weight(cpu_smt_mask(cpu));
+
+ if (weight > sched_smt_weight)
+ sched_smt_weight = weight;
+
+ /*
+ * When going up, increment the number of cores with SMT present.
+ */
+ if (cpumask_weight(cpu_smt_mask(cpu)) == 2)
+ static_branch_inc_cpuslocked(&sched_smt_present);
+ } while (0);
#endif
set_cpu_active(cpu, true);
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 125c020746b8..20b9255ebf97 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -6076,6 +6076,8 @@ static inline int __select_idle_cpu(int cpu, struct task_struct *p)
DEFINE_STATIC_KEY_FALSE(sched_smt_present);
EXPORT_SYMBOL_GPL(sched_smt_present);
+int __read_mostly sched_smt_weight = 1;
+
static inline void set_idle_cores(int cpu, int val)
{
struct sched_domain_shared *sds;
@@ -6194,6 +6196,8 @@ static inline bool test_idle_cores(int cpu, bool def)
return def;
}
+#define sched_smt_weight 1
+
static inline int select_idle_core(struct task_struct *p, int core, struct cpumask *cpus, int *idle_cpu)
{
return __select_idle_cpu(core, p);
@@ -6206,6 +6210,8 @@ static inline int select_idle_smt(struct task_struct *p, struct sched_domain *sd
#endif /* CONFIG_SCHED_SMT */
+#define sis_min_cores 2
+
/*
* Scan the LLC domain for idle CPUs; this is dynamically regulated by
* comparing the average scan cost (tracked in sd->avg_scan_cost) against the
@@ -6246,11 +6252,12 @@ static int select_idle_cpu(struct task_struct *p, struct sched_domain *sd, bool
avg_cost = this_sd->avg_scan_cost + 1;
span_avg = sd->span_weight * avg_idle;
- if (span_avg > 4*avg_cost)
+ if (span_avg > sis_min_cores * avg_cost)
nr = div_u64(span_avg, avg_cost);
else
- nr = 4;
+ nr = sis_min_cores;
+ nr *= sched_smt_weight;
time = cpu_clock(this);
}
diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
index e31179e6c6ff..4d47a0969710 100644
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -1351,6 +1351,8 @@ do { \
#ifdef CONFIG_SCHED_SMT
extern void __update_idle_core(struct rq *rq);
+extern int sched_smt_weight;
+
static inline void update_idle_core(struct rq *rq)
{
if (static_branch_unlikely(&sched_smt_present))
--
2.26.2