From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756236AbcIONMC (ORCPT ); Thu, 15 Sep 2016 09:12:02 -0400 Received: from foss.arm.com ([217.140.101.70]:36410 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752197AbcIONLz (ORCPT ); Thu, 15 Sep 2016 09:11:55 -0400 Subject: Re: [PATCH 4/7 v3] sched: propagate load during synchronous attach/detach To: Vincent Guittot , peterz@infradead.org, mingo@kernel.org, linux-kernel@vger.kernel.org, yuyang.du@intel.com, Morten.Rasmussen@arm.com References: <1473666472-13749-1-git-send-email-vincent.guittot@linaro.org> <1473666472-13749-5-git-send-email-vincent.guittot@linaro.org> Cc: linaro-kernel@lists.linaro.org, pjt@google.com, bsegall@google.com From: Dietmar Eggemann Message-ID: <896df1f8-c5ee-ae4c-46f0-4f4e76ad19b1@arm.com> Date: Thu, 15 Sep 2016 14:11:49 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Thunderbird/45.2.0 MIME-Version: 1.0 In-Reply-To: <1473666472-13749-5-git-send-email-vincent.guittot@linaro.org> Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 12/09/16 08:47, Vincent Guittot wrote: > When a task moves from/to a cfs_rq, we set a flag which is then used to > propagate the change at parent level (sched_entity and cfs_rq) during > next update. If the cfs_rq is throttled, the flag will stay pending until > the cfs_rw is unthrottled. > > For propagating the utilization, we copy the utilization of child cfs_rq to s/child/group ? > the sched_entity. > > For propagating the load, we have to take into account the load of the > whole task group in order to evaluate the load of the sched_entity. > Similarly to what was done before the rewrite of PELT, we add a correction > factor in case the task group's load is less than its share so it will > contribute the same load of a task of equal weight. What about cfs_rq->runnable_load_avg? [...] > +/* Take into account change of load of a child task group */ > +static inline void > +update_tg_cfs_load(struct cfs_rq *cfs_rq, struct sched_entity *se) > +{ > + struct cfs_rq *gcfs_rq = group_cfs_rq(se); > + long delta, load = gcfs_rq->avg.load_avg; > + > + /* If the load of group cfs_rq is null, the load of the > + * sched_entity will also be null so we can skip the formula > + */ > + if (load) { > + long tg_load; > + > + /* Get tg's load and ensure tg_load > 0 */ > + tg_load = atomic_long_read(&gcfs_rq->tg->load_avg) + 1; > + > + /* Ensure tg_load >= load and updated with current load*/ > + tg_load -= gcfs_rq->tg_load_avg_contrib; > + tg_load += load; > + > + /* scale gcfs_rq's load into tg's shares*/ > + load *= scale_load_down(gcfs_rq->tg->shares); > + load /= tg_load; > + > + /* > + * we need to compute a correction term in the case that the > + * task group is consuming <1 cpu so that we would contribute > + * the same load as a task of equal weight. Wasn't 'consuming <1' related to 'NICE_0_LOAD' and not scale_load_down(gcfs_rq->tg->shares) before the rewrite of PELT (v4.2, __update_group_entity_contrib())? > + */ > + if (tg_load < scale_load_down(gcfs_rq->tg->shares)) { > + load *= tg_load; > + load /= scale_load_down(gcfs_rq->tg->shares); > + } > + } [...]