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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: Ingo Molnar <mingo@elte.hu>
This commit is contained in:
Ingo Molnar 2007-10-15 17:00:18 +02:00
parent e5f32a3856
commit da84d96176
4 changed files with 38 additions and 0 deletions
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1
include/linux/sched.h
View File

@ -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;

27
kernel/sched.c
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@ -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;
}

2
kernel/sched_fair.c
View File

@ -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:
*/

8
kernel/sysctl.c
View File

@ -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,