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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id E802AC54EED for ; Mon, 30 Jan 2023 14:05:21 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S237050AbjA3OFV (ORCPT ); Mon, 30 Jan 2023 09:05:21 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:47626 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S237066AbjA3OFQ (ORCPT ); Mon, 30 Jan 2023 09:05:16 -0500 Received: from dfw.source.kernel.org (dfw.source.kernel.org [IPv6:2604:1380:4641:c500::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 48A1D1ADC2 for ; Mon, 30 Jan 2023 06:05:15 -0800 (PST) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id D72CE61036 for ; Mon, 30 Jan 2023 14:05:14 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id EE2D5C433D2; Mon, 30 Jan 2023 14:05:13 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1675087514; bh=DtPozjq3otwUFtiMwPh58GGZVMOrQ5hpDU2WH9qPGW0=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=k5Pu9RCacq0qlAsnPrGN1omAYZVCq/3Cg/3/23o4A90ofuxICoL3qHfn1aD0xOONr aWr4qQOVfgFeTa7K4oq/uO9atpOM06+qglk+lqNDqwIAPnOMr9pc0wU4LPY0+K3gG4 1Lfono+FxCqWrFwPWFetEWvE42zDqQ5wtweUHQzI= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Pierre Gondois , "Peter Zijlstra (Intel)" , Dietmar Eggemann , Vincent Guittot , Sasha Levin Subject: [PATCH 6.1 204/313] sched/fair: Check if prev_cpu has highest spare cap in feec() Date: Mon, 30 Jan 2023 14:50:39 +0100 Message-Id: <20230130134346.204278839@linuxfoundation.org> X-Mailer: git-send-email 2.39.1 In-Reply-To: <20230130134336.532886729@linuxfoundation.org> References: <20230130134336.532886729@linuxfoundation.org> User-Agent: quilt/0.67 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org From: Pierre Gondois [ Upstream commit ad841e569f5c88e3332b32a000f251f33ff32187 ] When evaluating the CPU candidates in the perf domain (pd) containing the previously used CPU (prev_cpu), find_energy_efficient_cpu() evaluates the energy of the pd: - without the task (base_energy) - with the task placed on prev_cpu (if the task fits) - with the task placed on the CPU with the highest spare capacity, prev_cpu being excluded from this set If prev_cpu is already the CPU with the highest spare capacity, max_spare_cap_cpu will be the CPU with the second highest spare capacity. On an Arm64 Juno-r2, with a workload of 10 tasks at a 10% duty cycle, when prev_cpu and max_spare_cap_cpu are both valid candidates, prev_spare_cap > max_spare_cap at ~82%. Thus the energy of the pd when placing the task on max_spare_cap_cpu is computed with no possible positive outcome 82% most of the time. Do not consider max_spare_cap_cpu as a valid candidate if prev_spare_cap > max_spare_cap. Signed-off-by: Pierre Gondois Signed-off-by: Peter Zijlstra (Intel) Reviewed-by: Dietmar Eggemann Reviewed-by: Vincent Guittot Link: https://lore.kernel.org/r/20221006081052.3862167-2-pierre.gondois@arm.com Stable-dep-of: e26fd28db828 ("sched/uclamp: Fix a uninitialized variable warnings") Signed-off-by: Sasha Levin --- kernel/sched/fair.c | 13 +++++++------ 1 file changed, 7 insertions(+), 6 deletions(-) diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index 0f32acb05055..bb04ca795fc3 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -7217,7 +7217,7 @@ static int find_energy_efficient_cpu(struct task_struct *p, int prev_cpu) unsigned long cur_delta, max_spare_cap = 0; unsigned long rq_util_min, rq_util_max; unsigned long util_min, util_max; - bool compute_prev_delta = false; + unsigned long prev_spare_cap = 0; int max_spare_cap_cpu = -1; unsigned long base_energy; @@ -7279,18 +7279,19 @@ static int find_energy_efficient_cpu(struct task_struct *p, int prev_cpu) if (cpu == prev_cpu) { /* Always use prev_cpu as a candidate. */ - compute_prev_delta = true; + prev_spare_cap = cpu_cap; } else if (cpu_cap > max_spare_cap) { /* * Find the CPU with the maximum spare capacity - * in the performance domain. + * among the remaining CPUs in the performance + * domain. */ max_spare_cap = cpu_cap; max_spare_cap_cpu = cpu; } } - if (max_spare_cap_cpu < 0 && !compute_prev_delta) + if (max_spare_cap_cpu < 0 && prev_spare_cap == 0) continue; eenv_pd_busy_time(&eenv, cpus, p); @@ -7298,7 +7299,7 @@ static int find_energy_efficient_cpu(struct task_struct *p, int prev_cpu) base_energy = compute_energy(&eenv, pd, cpus, p, -1); /* Evaluate the energy impact of using prev_cpu. */ - if (compute_prev_delta) { + if (prev_spare_cap > 0) { prev_delta = compute_energy(&eenv, pd, cpus, p, prev_cpu); /* CPU utilization has changed */ @@ -7309,7 +7310,7 @@ static int find_energy_efficient_cpu(struct task_struct *p, int prev_cpu) } /* Evaluate the energy impact of using max_spare_cap_cpu. */ - if (max_spare_cap_cpu >= 0) { + if (max_spare_cap_cpu >= 0 && max_spare_cap > prev_spare_cap) { cur_delta = compute_energy(&eenv, pd, cpus, p, max_spare_cap_cpu); /* CPU utilization has changed */ -- 2.39.0