Commit-ID: 1b568f0aabf280555125bc7cefc08321ff0ebaba
Gitweb: http://git.kernel.org/tip/1b568f0aabf280555125bc7cefc08321ff0ebaba
Author: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
AuthorDate: Mon, 9 May 2016 10:38:41 +0200
Committer: Ingo Molnar <mingo@xxxxxxxxxx>
CommitDate: Fri, 30 Sep 2016 11:03:26 +0200
sched/core: Optimize SCHED_SMT
Avoid pointless SCHED_SMT code when running on !SMT hardware.
Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: Mike Galbraith <efault@xxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: linux-kernel@xxxxxxxxxxxxxxx
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
---
kernel/sched/core.c | 19 +++++++++++++++++++
kernel/sched/fair.c | 8 +++++++-
kernel/sched/sched.h | 23 +++++++++++++++++------
3 files changed, 43 insertions(+), 7 deletions(-)
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 75ecd4f..9411545 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -7412,6 +7412,22 @@ int sched_cpu_dying(unsigned int cpu)
}
#endif
+#ifdef CONFIG_SCHED_SMT
+DEFINE_STATIC_KEY_FALSE(sched_smt_present);
+
+static void sched_init_smt(void)
+{
+ /*
+ * We've enumerated all CPUs and will assume that if any CPU
+ * has SMT siblings, CPU0 will too.
+ */
+ if (cpumask_weight(cpu_smt_mask(0)) > 1)
+ static_branch_enable(&sched_smt_present);
+}
+#else
+static inline void sched_init_smt(void) { }
+#endif
+
void __init sched_init_smp(void)
{
cpumask_var_t non_isolated_cpus;
@@ -7441,6 +7457,9 @@ void __init sched_init_smp(void)
init_sched_rt_class();
init_sched_dl_class();
+
+ sched_init_smt();
+
sched_smp_initialized = true;
}
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 6b41589..87caf2b 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -5357,7 +5357,7 @@ static inline bool test_idle_cores(int cpu, bool def)
* Since SMT siblings share all cache levels, inspecting this limited remote
* state should be fairly cheap.
*/
-void update_idle_core(struct rq *rq)
+void __update_idle_core(struct rq *rq)
{
int core = cpu_of(rq);
int cpu;
@@ -5389,6 +5389,9 @@ static int select_idle_core(struct task_struct *p, struct sched_domain *sd, int
struct cpumask *cpus = this_cpu_cpumask_var_ptr(select_idle_mask);
int core, cpu, wrap;
+ if (!static_branch_likely(&sched_smt_present))
+ return -1;
+
if (!test_idle_cores(target, false))
return -1;
@@ -5422,6 +5425,9 @@ static int select_idle_smt(struct task_struct *p, struct sched_domain *sd, int t
{
int cpu;
+ if (!static_branch_likely(&sched_smt_present))
+ return -1;
+
for_each_cpu(cpu, cpu_smt_mask(target)) {
if (!cpumask_test_cpu(cpu, tsk_cpus_allowed(p)))
continue;
diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
index c917dca..01b5189 100644
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -36,12 +36,6 @@ extern void cpu_load_update_active(struct rq *this_rq);
static inline void cpu_load_update_active(struct rq *this_rq) { }
#endif
-#ifdef CONFIG_SCHED_SMT
-extern void update_idle_core(struct rq *rq);
-#else
-static inline void update_idle_core(struct rq *rq) { }
-#endif
-
/*
* Helpers for converting nanosecond timing to jiffy resolution
*/
@@ -730,6 +724,23 @@ static inline int cpu_of(struct rq *rq)
#endif
}
+
+#ifdef CONFIG_SCHED_SMT
+
+extern struct static_key_false sched_smt_present;
+
+extern void __update_idle_core(struct rq *rq);
+
+static inline void update_idle_core(struct rq *rq)
+{
+ if (static_branch_unlikely(&sched_smt_present))
+ __update_idle_core(rq);
+}
+
+#else
+static inline void update_idle_core(struct rq *rq) { }
+#endif
+
DECLARE_PER_CPU_SHARED_ALIGNED(struct rq, runqueues);
#define cpu_rq(cpu) (&per_cpu(runqueues, (cpu)))
--
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