Messages in this thread |  | | Date | Thu, 9 Oct 2014 13:23:52 +0200 | From | Peter Zijlstra <> | Subject | Re: [PATCH v7 2/7] sched: move cfs task on a CPU with higher capacity |
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On Tue, Oct 07, 2014 at 02:13:32PM +0200, Vincent Guittot wrote: > +++ b/kernel/sched/fair.c > @@ -5896,6 +5896,18 @@ fix_small_capacity(struct sched_domain *sd, struct sched_group *group) > } > > /* > + * Check whether the capacity of the rq has been noticeably reduced by side > + * activity. The imbalance_pct is used for the threshold. > + * Return true is the capacity is reduced > + */ > +static inline int > +check_cpu_capacity(struct rq *rq, struct sched_domain *sd) > +{ > + return ((rq->cpu_capacity * sd->imbalance_pct) < > + (rq->cpu_capacity_orig * 100)); > +} > + > +/* > * Group imbalance indicates (and tries to solve) the problem where balancing > * groups is inadequate due to tsk_cpus_allowed() constraints. > * > @@ -6567,6 +6579,14 @@ static int need_active_balance(struct lb_env *env) > */ > if ((sd->flags & SD_ASYM_PACKING) && env->src_cpu > env->dst_cpu) > return 1; > + > + /* > + * The src_cpu's capacity is reduced because of other > + * sched_class or IRQs, we trig an active balance to move the > + * task > + */ > + if (check_cpu_capacity(env->src_rq, sd)) > + return 1; > }
So does it make sense to first check if there's a better candidate at all? By this time we've already iterated the current SD while trying regular load balancing, so we could know this.
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