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Commit da84d961 authored by Ingo Molnar's avatar Ingo Molnar
Browse files

sched: reintroduce cache-hot affinity 



reintroduce a simplified version of cache-hot/cold scheduling
affinity. This improves performance with certain SMP workloads,
such as sysbench.

Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
parent e5f32a38

include/linux/sched.h

+1 −0
Original line number Diff line number Diff line
@@ -1415,6 +1415,7 @@ extern unsigned int sysctl_sched_wakeup_granularity; 
extern unsigned int sysctl_sched_batch_wakeup_granularity;

extern unsigned int sysctl_sched_child_runs_first;

extern unsigned int sysctl_sched_features;

extern unsigned int sysctl_sched_migration_cost;

#endif



extern unsigned int sysctl_sched_compat_yield;

kernel/sched.c

+27 −0
Original line number Diff line number Diff line
@@ -2118,6 +2118,17 @@ static void pull_task(struct rq *src_rq, struct task_struct *p, 
	check_preempt_curr(this_rq, p);

}



/*

 * Is this task likely cache-hot:

 */

static inline int

task_hot(struct task_struct *p, unsigned long long now, struct sched_domain *sd)

{

	s64 delta = now - p->se.exec_start;



	return delta < (long long)sysctl_sched_migration_cost;

}



/*

 * can_migrate_task - may task p from runqueue rq be migrated to this_cpu?

 */
@@ -2139,6 +2150,22 @@ int can_migrate_task(struct task_struct *p, struct rq *rq, int this_cpu, 
	if (task_running(rq, p))

		return 0;



	/*

	 * Aggressive migration if:

	 * 1) task is cache cold, or

	 * 2) too many balance attempts have failed.

	 */



	if (sd->nr_balance_failed > sd->cache_nice_tries) {

#ifdef CONFIG_SCHEDSTATS

		if (task_hot(p, rq->clock, sd))

			schedstat_inc(sd, lb_hot_gained[idle]);

#endif

		return 1;

	}



	if (task_hot(p, rq->clock, sd))

		return 0;

	return 1;

}

kernel/sched_fair.c

+2 −0
Original line number Diff line number Diff line
@@ -74,6 +74,8 @@ const_debug unsigned int sysctl_sched_batch_wakeup_granularity = 10000000UL; 
 */

const_debug unsigned int sysctl_sched_wakeup_granularity = 10000000UL;



const_debug unsigned int sysctl_sched_migration_cost = 500000UL;



/**************************************************************

 * CFS operations on generic schedulable entities:

 */

kernel/sysctl.c

+8 −0
Original line number Diff line number Diff line
@@ -277,6 +277,14 @@ static ctl_table kern_table[] = { 
		.mode		= 0644,

		.proc_handler	= &proc_dointvec,

	},

	{

		.ctl_name	= CTL_UNNUMBERED,

		.procname	= "sched_migration_cost",

		.data		= &sysctl_sched_migration_cost,

		.maxlen		= sizeof(unsigned int),

		.mode		= 0644,

		.proc_handler	= &proc_dointvec,

	},

#endif

	{

		.ctl_name	= CTL_UNNUMBERED,