Messages in this thread Patch in this message | | | From | Alex Shi <> | Subject | [PATCH v5 3/7] sched: set initial value of runnable avg for new forked task | Date | Mon, 6 May 2013 09:45:07 +0800 |
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We need initialize the se.avg.{decay_count, load_avg_contrib} for a new forked task. Otherwise random values of above variables cause mess when do new task enqueue: enqueue_task_fair enqueue_entity enqueue_entity_load_avg
and make forking balancing imbalance since incorrect load_avg_contrib.
set avg.decay_count = 0, and avg.load_avg_contrib = se->load.weight to resolve such issues.
Signed-off-by: Alex Shi <alex.shi@intel.com> --- kernel/sched/core.c | 6 ++++++ kernel/sched/fair.c | 4 ++++ 2 files changed, 10 insertions(+)
diff --git a/kernel/sched/core.c b/kernel/sched/core.c index c8db984..ecec7f1 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -1566,6 +1566,7 @@ static void __sched_fork(struct task_struct *p) #ifdef CONFIG_SMP p->se.avg.runnable_avg_period = 0; p->se.avg.runnable_avg_sum = 0; + p->se.avg.decay_count = 0; #endif #ifdef CONFIG_SCHEDSTATS memset(&p->se.statistics, 0, sizeof(p->se.statistics)); @@ -1653,6 +1654,11 @@ void sched_fork(struct task_struct *p) p->sched_reset_on_fork = 0; } + /* New forked task assumed with full utilization */ +#if defined(CONFIG_SMP) + p->se.avg.load_avg_contrib = p->se.load.weight; +#endif + if (!rt_prio(p->prio)) p->sched_class = &fair_sched_class; diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index 9c2f726..2881d42 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -1508,6 +1508,10 @@ static inline void enqueue_entity_load_avg(struct cfs_rq *cfs_rq, * We track migrations using entity decay_count <= 0, on a wake-up * migration we use a negative decay count to track the remote decays * accumulated while sleeping. + * + * When enqueue a new forked task, the se->avg.decay_count == 0, so + * we bypass update_entity_load_avg(), use avg.load_avg_contrib initial + * value: se->load.weight. */ if (unlikely(se->avg.decay_count <= 0)) { se->avg.last_runnable_update = rq_of(cfs_rq)->clock_task; -- 1.7.12
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