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[91.160.61.128]) by smtp.gmail.com with ESMTPSA id p15sm5870123wrs.94.2019.10.18.06.26.43 (version=TLS1_2 cipher=ECDHE-RSA-AES128-SHA bits=128/128); Fri, 18 Oct 2019 06:26:44 -0700 (PDT) From: Vincent Guittot To: linux-kernel@vger.kernel.org, mingo@redhat.com, peterz@infradead.org Cc: pauld@redhat.com, valentin.schneider@arm.com, srikar@linux.vnet.ibm.com, quentin.perret@arm.com, dietmar.eggemann@arm.com, Morten.Rasmussen@arm.com, hdanton@sina.com, parth@linux.ibm.com, riel@surriel.com, Vincent Guittot Subject: [PATCH v4 01/11] sched/fair: clean up asym packing Date: Fri, 18 Oct 2019 15:26:28 +0200 Message-Id: <1571405198-27570-2-git-send-email-vincent.guittot@linaro.org> X-Mailer: git-send-email 2.7.4 In-Reply-To: <1571405198-27570-1-git-send-email-vincent.guittot@linaro.org> References: <1571405198-27570-1-git-send-email-vincent.guittot@linaro.org> Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Clean up asym packing to follow the default load balance behavior: - classify the group by creating a group_asym_packing field. - calculate the imbalance in calculate_imbalance() instead of bypassing it. We don't need to test twice same conditions anymore to detect asym packing and we consolidate the calculation of imbalance in calculate_imbalance(). There is no functional changes. Signed-off-by: Vincent Guittot Acked-by: Rik van Riel --- kernel/sched/fair.c | 63 ++++++++++++++--------------------------------------- 1 file changed, 16 insertions(+), 47 deletions(-) diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index 1f0a5e1..617145c 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -7675,6 +7675,7 @@ struct sg_lb_stats { unsigned int group_weight; enum group_type group_type; int group_no_capacity; + unsigned int group_asym_packing; /* Tasks should be moved to preferred CPU */ unsigned long group_misfit_task_load; /* A CPU has a task too big for its capacity */ #ifdef CONFIG_NUMA_BALANCING unsigned int nr_numa_running; @@ -8129,9 +8130,17 @@ static bool update_sd_pick_busiest(struct lb_env *env, * ASYM_PACKING needs to move all the work to the highest * prority CPUs in the group, therefore mark all groups * of lower priority than ourself as busy. + * + * This is primarily intended to used at the sibling level. Some + * cores like POWER7 prefer to use lower numbered SMT threads. In the + * case of POWER7, it can move to lower SMT modes only when higher + * threads are idle. When in lower SMT modes, the threads will + * perform better since they share less core resources. Hence when we + * have idle threads, we want them to be the higher ones. */ if (sgs->sum_nr_running && sched_asym_prefer(env->dst_cpu, sg->asym_prefer_cpu)) { + sgs->group_asym_packing = 1; if (!sds->busiest) return true; @@ -8273,51 +8282,6 @@ static inline void update_sd_lb_stats(struct lb_env *env, struct sd_lb_stats *sd } /** - * check_asym_packing - Check to see if the group is packed into the - * sched domain. - * - * This is primarily intended to used at the sibling level. Some - * cores like POWER7 prefer to use lower numbered SMT threads. In the - * case of POWER7, it can move to lower SMT modes only when higher - * threads are idle. When in lower SMT modes, the threads will - * perform better since they share less core resources. Hence when we - * have idle threads, we want them to be the higher ones. - * - * This packing function is run on idle threads. It checks to see if - * the busiest CPU in this domain (core in the P7 case) has a higher - * CPU number than the packing function is being run on. Here we are - * assuming lower CPU number will be equivalent to lower a SMT thread - * number. - * - * Return: 1 when packing is required and a task should be moved to - * this CPU. The amount of the imbalance is returned in env->imbalance. - * - * @env: The load balancing environment. - * @sds: Statistics of the sched_domain which is to be packed - */ -static int check_asym_packing(struct lb_env *env, struct sd_lb_stats *sds) -{ - int busiest_cpu; - - if (!(env->sd->flags & SD_ASYM_PACKING)) - return 0; - - if (env->idle == CPU_NOT_IDLE) - return 0; - - if (!sds->busiest) - return 0; - - busiest_cpu = sds->busiest->asym_prefer_cpu; - if (sched_asym_prefer(busiest_cpu, env->dst_cpu)) - return 0; - - env->imbalance = sds->busiest_stat.group_load; - - return 1; -} - -/** * fix_small_imbalance - Calculate the minor imbalance that exists * amongst the groups of a sched_domain, during * load balancing. @@ -8401,6 +8365,11 @@ static inline void calculate_imbalance(struct lb_env *env, struct sd_lb_stats *s local = &sds->local_stat; busiest = &sds->busiest_stat; + if (busiest->group_asym_packing) { + env->imbalance = busiest->group_load; + return; + } + if (busiest->group_type == group_imbalanced) { /* * In the group_imb case we cannot rely on group-wide averages @@ -8505,8 +8474,8 @@ static struct sched_group *find_busiest_group(struct lb_env *env) busiest = &sds.busiest_stat; /* ASYM feature bypasses nice load balance check */ - if (check_asym_packing(env, &sds)) - return sds.busiest; + if (busiest->group_asym_packing) + goto force_balance; /* There is no busy sibling group to pull tasks from */ if (!sds.busiest || busiest->sum_nr_running == 0) -- 2.7.4