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Merge branch 'sched-fixes-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip 

* 'sched-fixes-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip:
  sched: Fix kthread_bind() by moving the body of kthread_bind() to sched.c
  sched: Disable SD_PREFER_LOCAL at node level
  sched: Fix boot crash by zalloc()ing most of the cpu masks
  sched: Strengthen buddies and mitigate buddy induced latencies
This commit is contained in:
Linus Torvalds 2009-11-05 10:56:47 -08:00
parent 72cc129e8d b84ff7d6f1
commit 608221fdf9
4 changed files with 84 additions and 54 deletions
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2
arch/x86/include/asm/topology.h
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@ -143,7 +143,7 @@ extern unsigned long node_remap_size[];
| 1*SD_BALANCE_FORK \
| 0*SD_BALANCE_WAKE \
| 1*SD_WAKE_AFFINE \
| 1*SD_PREFER_LOCAL \
| 0*SD_PREFER_LOCAL \
| 0*SD_SHARE_CPUPOWER \
| 0*SD_POWERSAVINGS_BALANCE \
| 0*SD_SHARE_PKG_RESOURCES \

23
kernel/kthread.c
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@ -149,29 +149,6 @@ struct task_struct *kthread_create(int (*threadfn)(void *data),
}
EXPORT_SYMBOL(kthread_create);
/**
* kthread_bind - bind a just-created kthread to a cpu.
* @k: thread created by kthread_create().
* @cpu: cpu (might not be online, must be possible) for @k to run on.
*
* Description: This function is equivalent to set_cpus_allowed(),
* except that @cpu doesn't need to be online, and the thread must be
* stopped (i.e., just returned from kthread_create()).
*/
void kthread_bind(struct task_struct *k, unsigned int cpu)
{
/* Must have done schedule() in kthread() before we set_task_cpu */
if (!wait_task_inactive(k, TASK_UNINTERRUPTIBLE)) {
WARN_ON(1);
return;
}
set_task_cpu(k, cpu);
k->cpus_allowed = cpumask_of_cpu(cpu);
k->rt.nr_cpus_allowed = 1;
k->flags |= PF_THREAD_BOUND;
}
EXPORT_SYMBOL(kthread_bind);
/**
* kthread_stop - stop a thread created by kthread_create().
* @k: thread created by kthread_create().

40
kernel/sched.c
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@ -1992,6 +1992,38 @@ static inline void check_class_changed(struct rq *rq, struct task_struct *p,
p->sched_class->prio_changed(rq, p, oldprio, running);
}
/**
* kthread_bind - bind a just-created kthread to a cpu.
* @k: thread created by kthread_create().
* @cpu: cpu (might not be online, must be possible) for @k to run on.
*
* Description: This function is equivalent to set_cpus_allowed(),
* except that @cpu doesn't need to be online, and the thread must be
* stopped (i.e., just returned from kthread_create()).
*
* Function lives here instead of kthread.c because it messes with
* scheduler internals which require locking.
*/
void kthread_bind(struct task_struct *p, unsigned int cpu)
{
struct rq *rq = cpu_rq(cpu);
unsigned long flags;
/* Must have done schedule() in kthread() before we set_task_cpu */
if (!wait_task_inactive(p, TASK_UNINTERRUPTIBLE)) {
WARN_ON(1);
return;
}
spin_lock_irqsave(&rq->lock, flags);
set_task_cpu(p, cpu);
p->cpus_allowed = cpumask_of_cpu(cpu);
p->rt.nr_cpus_allowed = 1;
p->flags |= PF_THREAD_BOUND;
spin_unlock_irqrestore(&rq->lock, flags);
}
EXPORT_SYMBOL(kthread_bind);
#ifdef CONFIG_SMP
/*
* Is this task likely cache-hot:
@ -2004,7 +2036,7 @@ task_hot(struct task_struct *p, u64 now, struct sched_domain *sd)
/*
* Buddy candidates are cache hot:
*/
if (sched_feat(CACHE_HOT_BUDDY) &&
if (sched_feat(CACHE_HOT_BUDDY) && this_rq()->nr_running &&
(&p->se == cfs_rq_of(&p->se)->next ||
&p->se == cfs_rq_of(&p->se)->last))
return 1;
@ -9532,13 +9564,13 @@ void __init sched_init(void)
current->sched_class = &fair_sched_class;
/* Allocate the nohz_cpu_mask if CONFIG_CPUMASK_OFFSTACK */
alloc_cpumask_var(&nohz_cpu_mask, GFP_NOWAIT);
zalloc_cpumask_var(&nohz_cpu_mask, GFP_NOWAIT);
#ifdef CONFIG_SMP
#ifdef CONFIG_NO_HZ
alloc_cpumask_var(&nohz.cpu_mask, GFP_NOWAIT);
zalloc_cpumask_var(&nohz.cpu_mask, GFP_NOWAIT);
alloc_cpumask_var(&nohz.ilb_grp_nohz_mask, GFP_NOWAIT);
#endif
alloc_cpumask_var(&cpu_isolated_map, GFP_NOWAIT);
zalloc_cpumask_var(&cpu_isolated_map, GFP_NOWAIT);
#endif /* SMP */
perf_event_init();

73
kernel/sched_fair.c
View File

@ -822,6 +822,26 @@ check_preempt_tick(struct cfs_rq *cfs_rq, struct sched_entity *curr)
* re-elected due to buddy favours.
*/
clear_buddies(cfs_rq, curr);
return;
}
/*
* Ensure that a task that missed wakeup preemption by a
* narrow margin doesn't have to wait for a full slice.
* This also mitigates buddy induced latencies under load.
*/
if (!sched_feat(WAKEUP_PREEMPT))
return;
if (delta_exec < sysctl_sched_min_granularity)
return;
if (cfs_rq->nr_running > 1) {
struct sched_entity *se = __pick_next_entity(cfs_rq);
s64 delta = curr->vruntime - se->vruntime;
if (delta > ideal_runtime)
resched_task(rq_of(cfs_rq)->curr);
}
}
@ -861,21 +881,18 @@ wakeup_preempt_entity(struct sched_entity *curr, struct sched_entity *se);
static struct sched_entity *pick_next_entity(struct cfs_rq *cfs_rq)
{
struct sched_entity *se = __pick_next_entity(cfs_rq);
struct sched_entity *buddy;
struct sched_entity *left = se;
if (cfs_rq->next) {
buddy = cfs_rq->next;
cfs_rq->next = NULL;
if (wakeup_preempt_entity(buddy, se) < 1)
return buddy;
}
if (cfs_rq->next && wakeup_preempt_entity(cfs_rq->next, left) < 1)
se = cfs_rq->next;
if (cfs_rq->last) {
buddy = cfs_rq->last;
cfs_rq->last = NULL;
if (wakeup_preempt_entity(buddy, se) < 1)
return buddy;
}
/*
* Prefer last buddy, try to return the CPU to a preempted task.
*/
if (cfs_rq->last && wakeup_preempt_entity(cfs_rq->last, left) < 1)
se = cfs_rq->last;
clear_buddies(cfs_rq, se);
return se;
}
@ -1577,6 +1594,7 @@ static void check_preempt_wakeup(struct rq *rq, struct task_struct *p, int wake_
struct sched_entity *se = &curr->se, *pse = &p->se;
struct cfs_rq *cfs_rq = task_cfs_rq(curr);
int sync = wake_flags & WF_SYNC;
int scale = cfs_rq->nr_running >= sched_nr_latency;
update_curr(cfs_rq);
@ -1591,18 +1609,7 @@ static void check_preempt_wakeup(struct rq *rq, struct task_struct *p, int wake_
if (unlikely(se == pse))
return;
/*
* Only set the backward buddy when the current task is still on the
* rq. This can happen when a wakeup gets interleaved with schedule on
* the ->pre_schedule() or idle_balance() point, either of which can
* drop the rq lock.
*
* Also, during early boot the idle thread is in the fair class, for
* obvious reasons its a bad idea to schedule back to the idle thread.
*/
if (sched_feat(LAST_BUDDY) && likely(se->on_rq && curr != rq->idle))
set_last_buddy(se);
if (sched_feat(NEXT_BUDDY) && !(wake_flags & WF_FORK))
if (sched_feat(NEXT_BUDDY) && scale && !(wake_flags & WF_FORK))
set_next_buddy(pse);
/*
@ -1648,8 +1655,22 @@ static void check_preempt_wakeup(struct rq *rq, struct task_struct *p, int wake_
BUG_ON(!pse);
if (wakeup_preempt_entity(se, pse) == 1)
if (wakeup_preempt_entity(se, pse) == 1) {
resched_task(curr);
/*
* Only set the backward buddy when the current task is still
* on the rq. This can happen when a wakeup gets interleaved
* with schedule on the ->pre_schedule() or idle_balance()
* point, either of which can * drop the rq lock.
*
* Also, during early boot the idle thread is in the fair class,
* for obvious reasons its a bad idea to schedule back to it.
*/
if (unlikely(!se->on_rq || curr == rq->idle))
return;
if (sched_feat(LAST_BUDDY) && scale && entity_is_task(se))
set_last_buddy(se);
}
}
static struct task_struct *pick_next_task_fair(struct rq *rq)