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-rw-r--r--kernel/sched.c6
-rw-r--r--kernel/sched_fair.c32
-rw-r--r--kernel/sched_features.h1
3 files changed, 30 insertions, 9 deletions
diff --git a/kernel/sched.c b/kernel/sched.c
index e8819bc..82cc839 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -397,7 +397,7 @@ struct cfs_rq {
* 'curr' points to currently running entity on this cfs_rq.
* It is set to NULL otherwise (i.e when none are currently running).
*/
- struct sched_entity *curr, *next;
+ struct sched_entity *curr, *next, *last;
unsigned long nr_spread_over;
@@ -1805,7 +1805,9 @@ task_hot(struct task_struct *p, u64 now, struct sched_domain *sd)
/*
* Buddy candidates are cache hot:
*/
- if (sched_feat(CACHE_HOT_BUDDY) && (&p->se == cfs_rq_of(&p->se)->next))
+ if (sched_feat(CACHE_HOT_BUDDY) &&
+ (&p->se == cfs_rq_of(&p->se)->next ||
+ &p->se == cfs_rq_of(&p->se)->last))
return 1;
if (p->sched_class != &fair_sched_class)
diff --git a/kernel/sched_fair.c b/kernel/sched_fair.c
index ebd6de8..a6b1db8 100644
--- a/kernel/sched_fair.c
+++ b/kernel/sched_fair.c
@@ -341,9 +341,6 @@ static void __dequeue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se)
cfs_rq->rb_leftmost = next_node;
}
- if (cfs_rq->next == se)
- cfs_rq->next = NULL;
-
rb_erase(&se->run_node, &cfs_rq->tasks_timeline);
}
@@ -741,6 +738,12 @@ dequeue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int sleep)
#endif
}
+ if (cfs_rq->last == se)
+ cfs_rq->last = NULL;
+
+ if (cfs_rq->next == se)
+ cfs_rq->next = NULL;
+
if (se != cfs_rq->curr)
__dequeue_entity(cfs_rq, se);
account_entity_dequeue(cfs_rq, se);
@@ -798,10 +801,13 @@ static struct sched_entity *pick_next_entity(struct cfs_rq *cfs_rq)
{
struct sched_entity *se = __pick_next_entity(cfs_rq);
- if (!cfs_rq->next || wakeup_preempt_entity(cfs_rq->next, se) == 1)
- return se;
+ if (cfs_rq->next && wakeup_preempt_entity(cfs_rq->next, se) < 1)
+ return cfs_rq->next;
- return cfs_rq->next;
+ if (cfs_rq->last && wakeup_preempt_entity(cfs_rq->last, se) < 1)
+ return cfs_rq->last;
+
+ return se;
}
static void put_prev_entity(struct cfs_rq *cfs_rq, struct sched_entity *prev)
@@ -1319,10 +1325,11 @@ wakeup_preempt_entity(struct sched_entity *curr, struct sched_entity *se)
static void check_preempt_wakeup(struct rq *rq, struct task_struct *p, int sync)
{
struct task_struct *curr = rq->curr;
- struct cfs_rq *cfs_rq = task_cfs_rq(curr);
struct sched_entity *se = &curr->se, *pse = &p->se;
if (unlikely(rt_prio(p->prio))) {
+ struct cfs_rq *cfs_rq = task_cfs_rq(curr);
+
update_rq_clock(rq);
update_curr(cfs_rq);
resched_task(curr);
@@ -1335,6 +1342,17 @@ static void check_preempt_wakeup(struct rq *rq, struct task_struct *p, int sync)
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))
+ cfs_rq_of(se)->last = se;
cfs_rq_of(pse)->next = pse;
/*
diff --git a/kernel/sched_features.h b/kernel/sched_features.h
index fda0162..da5d93b 100644
--- a/kernel/sched_features.h
+++ b/kernel/sched_features.h
@@ -12,3 +12,4 @@ SCHED_FEAT(LB_BIAS, 1)
SCHED_FEAT(LB_WAKEUP_UPDATE, 1)
SCHED_FEAT(ASYM_EFF_LOAD, 1)
SCHED_FEAT(WAKEUP_OVERLAP, 0)
+SCHED_FEAT(LAST_BUDDY, 1)
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