Messages in this thread | | | Subject | Re: [PATCH v2] sched/fair: Remove setting task's se->runnable_weight during PELT update | From | Dietmar Eggemann <> | Date | Mon, 10 Sep 2018 16:49:05 -0700 |
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Hi,
On 08/03/2018 07:05 AM, Dietmar Eggemann wrote: > A CFS (SCHED_OTHER, SCHED_BATCH or SCHED_IDLE policy) task's > se->runnable_weight must always be in sync with its se->load.weight. > > se->runnable_weight is set to se->load.weight when the task is > forked (init_entity_runnable_average()) or reniced (reweight_entity()). > > There are two cases in set_load_weight() which since they currently only > set se->load.weight could lead to a situation in which se->load.weight > is different to se->runnable_weight for a CFS task: > > (1) A task switches to SCHED_IDLE. > > (2) A SCHED_FIFO, SCHED_RR or SCHED_DEADLINE task which has been reniced > (during which only its static priority gets set) switches to > SCHED_OTHER or SCHED_BATCH. > > Set se->runnable_weight to se->load.weight in these two cases to prevent > this. This eliminates the need to explicitly set it to se->load.weight > during PELT updates in the CFS scheduler fastpath. > > Signed-off-by: Dietmar Eggemann <dietmar.eggemann@arm.com> > --- > > Changes v1->v2: > - Rebased on latest tip/sched/core > > This patch has been tested w/ appropriate BUG_ON()'s in > __update_load_avg_blocked_se() and __update_load_avg_se() on an Ubuntu > 18.04 desktop. > > kernel/sched/core.c | 2 ++ > kernel/sched/pelt.c | 6 ------ > 2 files changed, 2 insertions(+), 6 deletions(-) > > diff --git a/kernel/sched/core.c b/kernel/sched/core.c > index deafa9fe602b..2a08418db3d1 100644 > --- a/kernel/sched/core.c > +++ b/kernel/sched/core.c > @@ -701,6 +701,7 @@ static void set_load_weight(struct task_struct *p, bool update_load) > if (idle_policy(p->policy)) { > load->weight = scale_load(WEIGHT_IDLEPRIO); > load->inv_weight = WMULT_IDLEPRIO; > + p->se.runnable_weight = load->weight; > return; > } > > @@ -713,6 +714,7 @@ static void set_load_weight(struct task_struct *p, bool update_load) > } else { > load->weight = scale_load(sched_prio_to_weight[prio]); > load->inv_weight = sched_prio_to_wmult[prio]; > + p->se.runnable_weight = load->weight; > } > } > > diff --git a/kernel/sched/pelt.c b/kernel/sched/pelt.c > index 35475c0c5419..d0016b16d23a 100644 > --- a/kernel/sched/pelt.c > +++ b/kernel/sched/pelt.c > @@ -269,9 +269,6 @@ ___update_load_avg(struct sched_avg *sa, unsigned long load, unsigned long runna > > int __update_load_avg_blocked_se(u64 now, int cpu, struct sched_entity *se) > { > - if (entity_is_task(se)) > - se->runnable_weight = se->load.weight; > - > if (___update_load_sum(now, cpu, &se->avg, 0, 0, 0)) { > ___update_load_avg(&se->avg, se_weight(se), se_runnable(se)); > return 1; > @@ -282,9 +279,6 @@ int __update_load_avg_blocked_se(u64 now, int cpu, struct sched_entity *se) > > int __update_load_avg_se(u64 now, int cpu, struct cfs_rq *cfs_rq, struct sched_entity *se) > { > - if (entity_is_task(se)) > - se->runnable_weight = se->load.weight; > - > if (___update_load_sum(now, cpu, &se->avg, !!se->on_rq, !!se->on_rq, > cfs_rq->curr == se)) { > >
Is there anything else I should do for this patch ?
Thanks,
-- Dietmar
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