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authorLinus Torvalds <torvalds@linux-foundation.org>2009-11-05 10:56:47 -0800
committerLinus Torvalds <torvalds@linux-foundation.org>2009-11-05 10:56:47 -0800
commit608221fdf9a2170962295dcfbea53dc5c50d1a74 (patch)
tree26712f2f8a8a332369df2b31174c8c5b46c42164 /kernel
parent72cc129e8dae988d2a132467cfd0ecd7623c35fb (diff)
parentb84ff7d6f1b7f8a43414e74d972ec4c8f3361db4 (diff)
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
Diffstat (limited to 'kernel')
-rw-r--r--kernel/kthread.c23
-rw-r--r--kernel/sched.c40
-rw-r--r--kernel/sched_fair.c73
3 files changed, 83 insertions, 53 deletions
diff --git a/kernel/kthread.c b/kernel/kthread.c
index 5fe709982ca..ab7ae57773e 100644
--- a/kernel/kthread.c
+++ b/kernel/kthread.c
@@ -150,29 +150,6 @@ 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().
*
diff --git a/kernel/sched.c b/kernel/sched.c
index a455dca884a..28dd4f490bf 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -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();
diff --git a/kernel/sched_fair.c b/kernel/sched_fair.c
index c32c3e643da..37087a7fac2 100644
--- a/kernel/sched_fair.c
+++ b/kernel/sched_fair.c
@@ -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)