On 9 October 2014 13:23, Peter Zijlstra <[email protected]> wrote: > 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.
i'm not sure to completely catch your point. Normally, f_b_g and f_b_q have already looked at the best candidate when we call need_active_balance. And src_cpu has been elected. Or i have missed your point ? > > -- 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/
