From: Byungchul Park <[email protected]> Especially in the case below, se->vruntime can be too large and scheduling cannot work properly.
1. set se->vruntime to "cfs_rq->min_vruntime - sysctl_sched_latency" in place_entity() when detaching the se from cfs_rq. 2. do a normalization by "se->vruntime -= cfs_rq->min_vruntime". (see detach_task_cfs_rq().) 3. do "se->vruntime += cfs_rq->min_vruntime", when attaching the se to a cfs_rq where cfs_rq->min_vruntime < sysctl_sched_latency. In this case, se->vruntime is suppose to be a negative value, but actually it is a too large value because vruntime is a unsigned type. It's wrong. To avoid this situation, this patch takes the case into account. Signed-off-by: Byungchul Park <[email protected]> --- kernel/sched/fair.c | 11 +++++++++-- 1 file changed, 9 insertions(+), 2 deletions(-) diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index 077076f..a7cc8e8 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -480,6 +480,13 @@ static void update_min_vruntime(struct cfs_rq *cfs_rq) #endif } +static inline void vruntime_unnormalize(struct cfs_rq *cfs_rq, struct sched_entity *se) +{ + se->vruntime += cfs_rq->min_vruntime; + if (unlikely((s64)se->vruntime < 0)) + se->vruntime = 0; +} + /* * Enqueue an entity into the rb-tree: */ @@ -3002,7 +3009,7 @@ enqueue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags) * through calling update_curr(). */ if (!(flags & ENQUEUE_WAKEUP) || (flags & ENQUEUE_WAKING)) - se->vruntime += cfs_rq->min_vruntime; + vruntime_unnormalize(cfs_rq, se); /* * Update run-time statistics of the 'current'. @@ -8019,7 +8026,7 @@ static void attach_task_cfs_rq(struct task_struct *p) attach_entity_load_avg(cfs_rq, se); if (!vruntime_normalized(p)) - se->vruntime += cfs_rq->min_vruntime; + vruntime_unnormalize(cfs_rq, se); } static void switched_from_fair(struct rq *rq, struct task_struct *p) -- 1.7.9.5 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
