From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-5.3 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 242DAC433E0 for ; Tue, 19 May 2020 10:28:37 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id F1AFC20758 for ; Tue, 19 May 2020 10:28:36 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728440AbgESK2g (ORCPT ); Tue, 19 May 2020 06:28:36 -0400 Received: from foss.arm.com ([217.140.110.172]:58452 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725911AbgESK2f (ORCPT ); Tue, 19 May 2020 06:28:35 -0400 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 060C2101E; Tue, 19 May 2020 03:28:35 -0700 (PDT) Received: from [192.168.0.7] (unknown [172.31.20.19]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id A7DA03F305; Tue, 19 May 2020 03:28:33 -0700 (PDT) Subject: Re: [PATCH v2] sched/pelt: sync util/runnable_sum with PELT window when propagating To: Vincent Guittot , mingo@redhat.com, peterz@infradead.org, juri.lelli@redhat.com, rostedt@goodmis.org, bsegall@google.com, mgorman@suse.de, linux-kernel@vger.kernel.org References: <20200506155301.14288-1-vincent.guittot@linaro.org> From: Dietmar Eggemann Message-ID: Date: Tue, 19 May 2020 12:28:28 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.7.0 MIME-Version: 1.0 In-Reply-To: <20200506155301.14288-1-vincent.guittot@linaro.org> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 06/05/2020 17:53, Vincent Guittot wrote: [...] > diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c > index 02f323b85b6d..df3923a65162 100644 > --- a/kernel/sched/fair.c > +++ b/kernel/sched/fair.c > @@ -3441,52 +3441,46 @@ static inline void > update_tg_cfs_util(struct cfs_rq *cfs_rq, struct sched_entity *se, struct cfs_rq *gcfs_rq) > { > long delta = gcfs_rq->avg.util_avg - se->avg.util_avg; > + /* > + * cfs_rq->avg.period_contrib can be used for both cfs_rq and se. > + * See ___update_load_avg() for details. > + */ > + u32 divider = LOAD_AVG_MAX - 1024 + cfs_rq->avg.period_contrib; Why not doing the assignment (like in update_tg_cfs_load()) after the next condition? Same question for update_tg_cfs_runnable(). [...] > static inline void > update_tg_cfs_runnable(struct cfs_rq *cfs_rq, struct sched_entity *se, struct cfs_rq *gcfs_rq) > { > long delta = gcfs_rq->avg.runnable_avg - se->avg.runnable_avg; > + /* > + * cfs_rq->avg.period_contrib can be used for both cfs_rq and se. > + * See ___update_load_avg() for details. > + */ > + u32 divider = LOAD_AVG_MAX - 1024 + cfs_rq->avg.period_contrib; We know have 6 assignments like this in fair.c and 1 in pelt.c. Could this not be refactored by using something like this in pelt.h: +static inline u32 get_divider(struct sched_avg *avg) +{ + return LOAD_AVG_MAX - 1024 + avg->period_contrib; +} [...] > diff --git a/kernel/sched/pelt.c b/kernel/sched/pelt.c > index b647d04d9c8b..1feff80e7e45 100644 > --- a/kernel/sched/pelt.c > +++ b/kernel/sched/pelt.c > @@ -237,6 +237,30 @@ ___update_load_sum(u64 now, struct sched_avg *sa, > return 1; > } > > +/* > + * When syncing *_avg with *_sum, we must take into account the current > + * position in the PELT segment otherwise the remaining part of the segment > + * will be considered as idle time whereas it's not yet elapsed and this will > + * generate unwanted oscillation in the range [1002..1024[. > + * > + * The max value of *_sum varies with the position in the time segment and is > + * equals to : > + * > + * LOAD_AVG_MAX*y + sa->period_contrib > + * > + * which can be simplified into: > + * > + * LOAD_AVG_MAX - 1024 + sa->period_contrib > + * > + * because LOAD_AVG_MAX*y == LOAD_AVG_MAX-1024 Isn't this rather '~' instead of '==', even for y^32 = 0.5 ? 47742 * 0.5^(1/32) ~ 47742 - 1024 Apart from that, LGTM Reviewed-by: Dietmar Eggemann