Messages in this thread | | | From | Vincent Guittot <> | Date | Thu, 11 Sep 2014 19:26:48 +0200 | Subject | Re: [PATCH v5 11/12] sched: replace capacity_factor by utilization |
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On 11 September 2014 18:15, Peter Zijlstra <peterz@infradead.org> wrote: > On Tue, Aug 26, 2014 at 01:06:54PM +0200, Vincent Guittot wrote: >> +static inline int group_has_free_capacity(struct sg_lb_stats *sgs, >> + struct lb_env *env) >> { >> + if ((sgs->group_capacity_orig * 100) > >> + (sgs->group_utilization * env->sd->imbalance_pct)) >> + return 1; >> + >> + if (sgs->sum_nr_running < sgs->group_weight) >> + return 1; >> >> + return 0; >> +} >> >> +static inline int group_is_overloaded(struct sg_lb_stats *sgs, >> + struct lb_env *env) >> +{ >> + if (sgs->sum_nr_running <= sgs->group_weight) >> + return 0; >> >> + if ((sgs->group_capacity_orig * 100) < >> + (sgs->group_utilization * env->sd->imbalance_pct)) >> + return 1; >> >> + return 0; >> } > > I'm confused about the utilization vs capacity_orig. I see how we should
1st point is that I should compare utilization vs capacity and not capacity_orig. I should have replaced capacity_orig by capacity in the functions above when i move the utilization statistic from rq->avg.runnable_avg_sum to cfs.usage_load_avg. rq->avg.runnable_avg_sum was measuring all activity on the cpu whereas cfs.usage_load_avg integrates only cfs tasks
With this change, we don't need sgs->group_capacity_orig anymore but only sgs->group_capacity. So sgs->group_capacity_orig can be removed as it's no more used in the code as sg_capacity_factor has been removed
> maybe scale things with the capacity when comparing between CPUs/groups, > but not on the same CPU/group. > > I would have expected something simple like: > > static inline bool group_has_capacity() > { > /* Is there a spare cycle? */ > if (sgs->group_utilization < sgs->group_weight * SCHED_LOAD_SCALE) > return true; > > /* Are there less tasks than logical CPUs? */ > if (sgs->sum_nr_running < sgs->group_weight) > return true; > > return false; > } > > Where group_utilization a pure sum of running_avg. > > Now this has a hole when there are RT tasks on the system, in that case > the utilization will never hit 1, but we could fix that another way. I > don't think the capacity_orig thing is right.
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