Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753447AbaFWMwy (ORCPT ); Mon, 23 Jun 2014 08:52:54 -0400 Received: from bombadil.infradead.org ([198.137.202.9]:59189 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751066AbaFWMww (ORCPT ); Mon, 23 Jun 2014 08:52:52 -0400 Date: Mon, 23 Jun 2014 14:52:33 +0200 From: Peter Zijlstra To: Tim Chen Cc: Ingo Molnar , Andi Kleen , Michel Lespinasse , Rik van Riel , Peter Hurley , Jason Low , Davidlohr Bueson , linux-kernel@vger.kernel.org Subject: Re: [PATCH v2] sched: Fast idling of CPU when system is partially loaded Message-ID: <20140623125233.GZ19860@laptop.programming.kicks-ass.net> References: <1402948127.2970.578.camel@schen9-DESK> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1402948127.2970.578.camel@schen9-DESK> User-Agent: Mutt/1.5.21 (2012-12-30) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Jun 16, 2014 at 12:48:47PM -0700, Tim Chen wrote: > +++ b/kernel/sched/fair.c > @@ -5863,7 +5863,8 @@ static inline int sg_capacity(struct lb_env *env, struct sched_group *group) > */ > static inline void update_sg_lb_stats(struct lb_env *env, > struct sched_group *group, int load_idx, > - int local_group, struct sg_lb_stats *sgs) > + int local_group, struct sg_lb_stats *sgs, > + bool *overload) > { > unsigned long load; > int i; > @@ -5881,6 +5882,8 @@ static inline void update_sg_lb_stats(struct lb_env *env, > > sgs->group_load += load; > sgs->sum_nr_running += rq->nr_running; > + if (overload && rq->nr_running > 1) > + *overload = true; > #ifdef CONFIG_NUMA_BALANCING > sgs->nr_numa_running += rq->nr_numa_running; > sgs->nr_preferred_running += rq->nr_preferred_running; > @@ -5991,6 +5994,7 @@ static inline void update_sd_lb_stats(struct lb_env *env, struct sd_lb_stats *sd > struct sched_group *sg = env->sd->groups; > struct sg_lb_stats tmp_sgs; > int load_idx, prefer_sibling = 0; > + bool overload = false; > > if (child && child->flags & SD_PREFER_SIBLING) > prefer_sibling = 1; > @@ -6011,7 +6015,13 @@ static inline void update_sd_lb_stats(struct lb_env *env, struct sd_lb_stats *sd > update_group_power(env->sd, env->dst_cpu); > } > > - update_sg_lb_stats(env, sg, load_idx, local_group, sgs); > + if (env->sd->parent) > + update_sg_lb_stats(env, sg, load_idx, local_group, sgs, > + NULL); > + else > + /* gather overload info if we are at root domain */ > + update_sg_lb_stats(env, sg, load_idx, local_group, sgs, > + &overload); > > if (local_group) > goto next_group; > @@ -6045,6 +6055,13 @@ next_group: > > if (env->sd->flags & SD_NUMA) > env->fbq_type = fbq_classify_group(&sds->busiest_stat); > + > + if (!env->sd->parent) { > + /* update overload indicator if we are at root domain */ > + if (env->dst_rq->rd->overload != overload) > + env->dst_rq->rd->overload = overload; > + } > + > } > > /** So I don't get why we can't do the below; I think Jason tried to ask the same... Making that overload thing unconditional makes the code simpler and the cost is about the same; it doesn't matter if we test the pointer or ->nr_running, which we've already loaded anyhow. Also, with only having a single update_sg_lb_stats() callsite GCC can more easily inline the lot. --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -5886,7 +5886,7 @@ static inline void update_sg_lb_stats(st sgs->group_load += load; sgs->sum_nr_running += rq->nr_running; - if (overload && rq->nr_running > 1) + if (rq->nr_running > 1) *overload = true; #ifdef CONFIG_NUMA_BALANCING sgs->nr_numa_running += rq->nr_numa_running; @@ -6019,13 +6019,7 @@ static inline void update_sd_lb_stats(st update_group_capacity(env->sd, env->dst_cpu); } - if (env->sd->parent) - update_sg_lb_stats(env, sg, load_idx, local_group, sgs, - NULL); - else - /* gather overload info if we are at root domain */ - update_sg_lb_stats(env, sg, load_idx, local_group, sgs, - &overload); + update_sg_lb_stats(env, sg, load_idx, local_group, sgs, &overload); if (local_group) goto next_group; @@ -6065,7 +6059,6 @@ static inline void update_sd_lb_stats(st if (env->dst_rq->rd->overload != overload) env->dst_rq->rd->overload = overload; } - } /** -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/