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| author | Peter Zijlstra <peterz@infradead.org> | 2016-05-09 08:38:41 (GMT) |
|---|---|---|
| committer | Ingo Molnar <mingo@kernel.org> | 2016-09-30 09:03:26 (GMT) |
| commit | 1b568f0aabf280555125bc7cefc08321ff0ebaba (patch) | |
| tree | 5ca491fb2b8a7ff46af700bc64c2d83cea68eabb | |
| parent | 10e2f1acd0106c05229f94c70a344ce3a2c8008b (diff) | |
| download | linux-1b568f0aabf280555125bc7cefc08321ff0ebaba.tar.xz | |
sched/core: Optimize SCHED_SMT
Avoid pointless SCHED_SMT code when running on !SMT hardware.
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
| -rw-r--r-- | kernel/sched/core.c | 19 | ||||
| -rw-r--r-- | kernel/sched/fair.c | 8 | ||||
| -rw-r--r-- | 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))) |