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Commit 1b568f0a authored by Peter Zijlstra's avatar Peter Zijlstra Committed by Ingo Molnar
Browse files

sched/core: Optimize SCHED_SMT 



Avoid pointless SCHED_SMT code when running on !SMT hardware.

Signed-off-by: default avatarPeter 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: default avatarIngo Molnar <mingo@kernel.org>
parent 10e2f1ac

kernel/sched/core.c

+19 −0
Original line number Diff line number Diff line
@@ -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;

}

kernel/sched/fair.c

+7 −1
Original line number Diff line number Diff line
@@ -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;

kernel/sched/sched.h

+17 −6
Original line number Diff line number Diff line
@@ -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)))