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Fri, 19 Jul 2019 13:12:56 +0000 Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id 5158020B99A76; Fri, 19 Jul 2019 15:12:55 +0200 (CEST) Date: Fri, 19 Jul 2019 15:12:55 +0200 From: Peter Zijlstra To: Vincent Guittot Cc: linux-kernel@vger.kernel.org, mingo@redhat.com, quentin.perret@arm.com, dietmar.eggemann@arm.com, Morten.Rasmussen@arm.com, pauld@redhat.com Subject: Re: [PATCH 3/5] sched/fair: rework load_balance Message-ID: <20190719131255.GL3419@hirez.programming.kicks-ass.net> References: <1563523105-24673-1-git-send-email-vincent.guittot@linaro.org> <1563523105-24673-4-git-send-email-vincent.guittot@linaro.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1563523105-24673-4-git-send-email-vincent.guittot@linaro.org> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Jul 19, 2019 at 09:58:23AM +0200, Vincent Guittot wrote: > @@ -8029,17 +8063,24 @@ static inline void update_sg_lb_stats(struct lb_env *env, > } > } > > - /* Adjust by relative CPU capacity of the group */ > - sgs->group_capacity = group->sgc->capacity; > - sgs->avg_load = (sgs->group_load*SCHED_CAPACITY_SCALE) / sgs->group_capacity; > + /* Check if dst cpu is idle and preferred to this group */ > + if (env->sd->flags & SD_ASYM_PACKING && > + env->idle != CPU_NOT_IDLE && > + sgs->sum_h_nr_running && > + sched_asym_prefer(env->dst_cpu, group->asym_prefer_cpu)) { > + sgs->group_asym_capacity = 1; > + } > > - if (sgs->sum_h_nr_running) > - sgs->load_per_task = sgs->group_load / sgs->sum_h_nr_running; > + sgs->group_capacity = group->sgc->capacity; > > sgs->group_weight = group->group_weight; > > - sgs->group_no_capacity = group_is_overloaded(env, sgs); > - sgs->group_type = group_classify(group, sgs); > + sgs->group_type = group_classify(env, group, sgs); > + > + /* Computing avg_load makes sense only when group is overloaded */ > + if (sgs->group_type != group_overloaded) The comment seems to suggest you meant: == > + sgs->avg_load = (sgs->group_load*SCHED_CAPACITY_SCALE) / > + sgs->group_capacity; > } > > /** > @@ -8070,7 +8111,7 @@ static bool update_sd_pick_busiest(struct lb_env *env, > */ > if (sgs->group_type == group_misfit_task && > (!group_smaller_max_cpu_capacity(sg, sds->local) || > - !group_has_capacity(env, &sds->local_stat))) > + sds->local_stat.group_type != group_has_spare)) > return false; > > if (sgs->group_type > busiest->group_type) > @@ -8079,11 +8120,18 @@ static bool update_sd_pick_busiest(struct lb_env *env, > if (sgs->group_type < busiest->group_type) > return false; > > - if (sgs->avg_load <= busiest->avg_load) > + /* Select the overloaded group with highest avg_load */ > + if (sgs->group_type == group_overloaded && > + sgs->avg_load <= busiest->avg_load) And this code does too; because with the above '!=', you're comparing uninitialized data here, no? > + return false; > + > + /* Prefer to move from lowest priority CPU's work */ > + if (sgs->group_type == group_asym_capacity && sds->busiest && > + sched_asym_prefer(sg->asym_prefer_cpu, sds->busiest->asym_prefer_cpu)) > return false; > > if (!(env->sd->flags & SD_ASYM_CPUCAPACITY)) > - goto asym_packing; > + goto spare_capacity; > > /* > * Candidate sg has no more than one task per CPU and