Extracted from a "sched-misc-bits.patch" patch from Peter Zijlstra . Signed-off-by: Mathieu Desnoyers CC: Peter Zijlstra --- kernel/sched_fair.c | 10 +++++++--- 1 file changed, 7 insertions(+), 3 deletions(-) Index: linux-2.6-lttng.git/kernel/sched_fair.c =================================================================== --- linux-2.6-lttng.git.orig/kernel/sched_fair.c +++ linux-2.6-lttng.git/kernel/sched_fair.c @@ -1647,7 +1647,11 @@ static void check_preempt_wakeup(struct struct task_struct *curr = rq->curr; struct sched_entity *se = &curr->se, *pse = &p->se; struct cfs_rq *cfs_rq = task_cfs_rq(curr); - int scale = cfs_rq->nr_running >= sched_nr_latency; + /* + * The buddy logic doesn't work well when there's not actually enough + * tasks for there to be buddies. + */ + int buddies = (cfs_rq->nr_running >= 2); if (unlikely(rt_prio(p->prio))) goto preempt; @@ -1658,7 +1662,7 @@ static void check_preempt_wakeup(struct if (unlikely(se == pse)) return; - if (sched_feat(NEXT_BUDDY) && scale && !(wake_flags & WF_FORK)) + if (sched_feat(NEXT_BUDDY) && buddies && !(wake_flags & WF_FORK)) set_next_buddy(pse); /* @@ -1704,7 +1708,7 @@ preempt: if (unlikely(!se->on_rq || curr == rq->idle)) return; - if (sched_feat(LAST_BUDDY) && scale && entity_is_task(se)) + if (sched_feat(LAST_BUDDY) && buddies && entity_is_task(se)) set_last_buddy(se); } -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/