Commit e5a710d1 authored by Linus Torvalds's avatar Linus Torvalds
Browse files

Merge tag 'sched-urgent-2023-09-17' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 

Pull scheduler fixes from Ingo Molnar:
 "Fix a performance regression on large SMT systems, an Intel SMT4
  balancing bug, and a topology setup bug on (Intel) hybrid processors"

* tag 'sched-urgent-2023-09-17' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  x86/sched: Restore the SD_ASYM_PACKING flag in the DIE domain
  sched/fair: Fix SMT4 group_smt_balance handling
  sched/fair: Optimize should_we_balance() for large SMT systems
parents e54ca3c8 108af4b4

arch/x86/kernel/smpboot.c

+9 −3
Original line number Diff line number Diff line
@@ -579,7 +579,6 @@ static bool match_llc(struct cpuinfo_x86 *c, struct cpuinfo_x86 *o) 
}





#if defined(CONFIG_SCHED_SMT) || defined(CONFIG_SCHED_CLUSTER) || defined(CONFIG_SCHED_MC)

static inline int x86_sched_itmt_flags(void)

{

	return sysctl_sched_itmt_enabled ? SD_ASYM_PACKING : 0;
@@ -603,7 +602,14 @@ static int x86_cluster_flags(void) 
	return cpu_cluster_flags() | x86_sched_itmt_flags();

}

#endif

#endif



static int x86_die_flags(void)

{

	if (cpu_feature_enabled(X86_FEATURE_HYBRID_CPU))

	       return x86_sched_itmt_flags();



	return 0;

}



/*

 * Set if a package/die has multiple NUMA nodes inside.
@@ -640,7 +646,7 @@ static void __init build_sched_topology(void) 
	 */

	if (!x86_has_numa_in_package) {

		x86_topology[i++] = (struct sched_domain_topology_level){

			cpu_cpu_mask, SD_INIT_NAME(DIE)

			cpu_cpu_mask, x86_die_flags, SD_INIT_NAME(DIE)

		};

	}

kernel/sched/fair.c

+25 −2
Original line number Diff line number Diff line
@@ -6619,6 +6619,7 @@ static void dequeue_task_fair(struct rq *rq, struct task_struct *p, int flags) 
/* Working cpumask for: load_balance, load_balance_newidle. */

static DEFINE_PER_CPU(cpumask_var_t, load_balance_mask);

static DEFINE_PER_CPU(cpumask_var_t, select_rq_mask);

static DEFINE_PER_CPU(cpumask_var_t, should_we_balance_tmpmask);



#ifdef CONFIG_NO_HZ_COMMON
@@ -9579,7 +9580,7 @@ static inline long sibling_imbalance(struct lb_env *env, 
	imbalance /= ncores_local + ncores_busiest;



	/* Take advantage of resource in an empty sched group */

	if (imbalance == 0 && local->sum_nr_running == 0 &&

	if (imbalance <= 1 && local->sum_nr_running == 0 &&

	    busiest->sum_nr_running > 1)

		imbalance = 2;
@@ -9767,6 +9768,15 @@ static bool update_sd_pick_busiest(struct lb_env *env, 
		break;



	case group_smt_balance:

		/*

		 * Check if we have spare CPUs on either SMT group to

		 * choose has spare or fully busy handling.

		 */

		if (sgs->idle_cpus != 0 || busiest->idle_cpus != 0)

			goto has_spare;



		fallthrough;



	case group_fully_busy:

		/*

		 * Select the fully busy group with highest avg_load. In
@@ -9806,6 +9816,7 @@ static bool update_sd_pick_busiest(struct lb_env *env, 
			else

				return true;

		}

has_spare:



		/*

		 * Select not overloaded group with lowest number of idle cpus
@@ -10917,6 +10928,7 @@ static int active_load_balance_cpu_stop(void *data); 


static int should_we_balance(struct lb_env *env)

{

	struct cpumask *swb_cpus = this_cpu_cpumask_var_ptr(should_we_balance_tmpmask);

	struct sched_group *sg = env->sd->groups;

	int cpu, idle_smt = -1;
@@ -10940,8 +10952,9 @@ static int should_we_balance(struct lb_env *env) 
		return 1;

	}



	cpumask_copy(swb_cpus, group_balance_mask(sg));

	/* Try to find first idle CPU */

	for_each_cpu_and(cpu, group_balance_mask(sg), env->cpus) {

	for_each_cpu_and(cpu, swb_cpus, env->cpus) {

		if (!idle_cpu(cpu))

			continue;
@@ -10953,6 +10966,14 @@ static int should_we_balance(struct lb_env *env) 
		if (!(env->sd->flags & SD_SHARE_CPUCAPACITY) && !is_core_idle(cpu)) {

			if (idle_smt == -1)

				idle_smt = cpu;

			/*

			 * If the core is not idle, and first SMT sibling which is

			 * idle has been found, then its not needed to check other

			 * SMT siblings for idleness:

			 */

#ifdef CONFIG_SCHED_SMT

			cpumask_andnot(swb_cpus, swb_cpus, cpu_smt_mask(cpu));

#endif

			continue;

		}
@@ -12918,6 +12939,8 @@ __init void init_sched_fair_class(void) 
	for_each_possible_cpu(i) {

		zalloc_cpumask_var_node(&per_cpu(load_balance_mask, i), GFP_KERNEL, cpu_to_node(i));

		zalloc_cpumask_var_node(&per_cpu(select_rq_mask,    i), GFP_KERNEL, cpu_to_node(i));

		zalloc_cpumask_var_node(&per_cpu(should_we_balance_tmpmask, i),

					GFP_KERNEL, cpu_to_node(i));



#ifdef CONFIG_CFS_BANDWIDTH

		INIT_CSD(&cpu_rq(i)->cfsb_csd, __cfsb_csd_unthrottle, cpu_rq(i));