From nobody Sat Sep 13 06:20:08 2025 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 4FCA9CD13D1 for ; Sat, 16 Sep 2023 23:35:39 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235376AbjIPXa3 (ORCPT ); Sat, 16 Sep 2023 19:30:29 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:36856 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232530AbjIPXaT (ORCPT ); Sat, 16 Sep 2023 19:30:19 -0400 Received: from mail-wm1-x329.google.com (mail-wm1-x329.google.com [IPv6:2a00:1450:4864:20::329]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id AE345CD1 for ; Sat, 16 Sep 2023 16:30:11 -0700 (PDT) Received: by mail-wm1-x329.google.com with SMTP id 5b1f17b1804b1-404314388ceso35094835e9.2 for ; Sat, 16 Sep 2023 16:30:11 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=layalina-io.20230601.gappssmtp.com; s=20230601; t=1694907010; x=1695511810; darn=vger.kernel.org; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:from:to:cc:subject:date :message-id:reply-to; bh=OWEM5rFnaxOpgcGqQ9iXm3kgW4XrovKW3FNIx9UUP3U=; b=aX0OVGvG8a6WCDG1Hz5uw3UYiluU7DKtM7LcqqRaPC7q20kcZsaG3q6KimWyKqCaLP kGi/+c+KzTZQMjnmMH2vnBjHmv4Kx84zMDNqUT8SzqHZHl4Em5B6ev56jk7SvyXQZrR9 WPqX7Y9TBes7u+Z8ayKNE4VvYuJMbVJRP1Lh4xnRVprv5v8XRX/XuuW9JL15miZC0vzi AJyQkSmVH5hfdRK3+DZnzZNqW3BegBN1Pb08eUaBSm32EyzYACz6nmKLIAR0Yu7Tol4a gUJTszRXy338qUC336Dv3t2sONouPtOraFMp2Qm0Id3v1FRBBgx588EFtxZ8lpxiRUun swUg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1694907010; x=1695511810; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:x-gm-message-state:from:to:cc :subject:date:message-id:reply-to; bh=OWEM5rFnaxOpgcGqQ9iXm3kgW4XrovKW3FNIx9UUP3U=; b=oGWSGD3JTZdyfQm1LRjS97TtuN4TZWy3EvfARTRiveut6tlp5DTJemG9lTsgftbhWS kRLMyct6YjtKERHvmdFTe0lJeAoIE4kF9fLAZ3RY99be6/oP6jIqv/S302Sxh8fIXcsD dAB4csUTFpaRSuAlXLvU/sxolw+vgKClft12/m/ILqt0wfCXWfMPDQXuDcXsXMhC668H WUbF8yNbRlvcQN2mLJIacC9vTyHCBhR6YaL58GMSSITZHlS7dSLSdWiKrHzlckp2vVA3 HwwYjjf8RDf37Qa6CL7GSRRgyFYEeB8rK2nT1n/X7uUpX8aXPXCJT6NXfCv9Fo8J5P9+ UAJg== X-Gm-Message-State: AOJu0YxlWo5aqNQtwGVhIXQoTgBpcIzA6OEc1shfmkbKNrxTDORZZU7G ZR+ajUPd3zeaXrP/E/oWuCChzg== X-Google-Smtp-Source: AGHT+IH8zt9b/coOQ/xxZj95zGbY/KfbY9VgHNql/0TMbF0y5DIMj6gMNv9nWvsWMlFWXyyAhIvdwQ== X-Received: by 2002:a1c:7407:0:b0:3fd:30cb:18bd with SMTP id p7-20020a1c7407000000b003fd30cb18bdmr4936651wmc.15.1694907009520; Sat, 16 Sep 2023 16:30:09 -0700 (PDT) Received: from airbuntu.. (host109-151-228-137.range109-151.btcentralplus.com. [109.151.228.137]) by smtp.gmail.com with ESMTPSA id b14-20020a05600c11ce00b003fee8502999sm11203929wmi.18.2023.09.16.16.30.08 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sat, 16 Sep 2023 16:30:09 -0700 (PDT) From: Qais Yousef To: Ingo Molnar , Peter Zijlstra , Vincent Guittot , Dietmar Eggemann Cc: linux-kernel@vger.kernel.org, Lukasz Luba , Wei Wang , Xuewen Yan , Hank , Jonathan JMChen , Hongyan Xia , Qais Yousef Subject: [PATCH v5 1/3] sched/uclamp: Set max_spare_cap_cpu even if max_spare_cap is 0 Date: Sun, 17 Sep 2023 00:29:53 +0100 Message-Id: <20230916232955.2099394-2-qyousef@layalina.io> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20230916232955.2099394-1-qyousef@layalina.io> References: <20230916232955.2099394-1-qyousef@layalina.io> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" When uclamp_max is being used, the util of the task could be higher than the spare capacity of the CPU, but due to uclamp_max value we force fit it there. The way the condition for checking for max_spare_cap in find_energy_efficient_cpu() was constructed; it ignored any CPU that has its spare_cap less than or _equal_ to max_spare_cap. Since we initialize max_spare_cap to 0; this lead to never setting max_spare_cap_cpu and hence ending up never performing compute_energy() for this cluster and missing an opportunity for a better energy efficient placement to honour uclamp_max setting. max_spare_cap =3D 0; cpu_cap =3D capacity_of(cpu) - cpu_util(p); // 0 if cpu_util(p) is high ... util_fits_cpu(...); // will return true if uclamp_max forces it to fit ... // this logic will fail to update max_spare_cap_cpu if cpu_cap is 0 if (cpu_cap > max_spare_cap) { max_spare_cap =3D cpu_cap; max_spare_cap_cpu =3D cpu; } prev_spare_cap suffers from a similar problem. Fix the logic by converting the variables into long and treating -1 value as 'not populated' instead of 0 which is a viable and correct spare capacity value. We need to be careful signed comparison is used when comparing with cpu_cap in one of the conditions. Fixes: 1d42509e475c ("sched/fair: Make EAS wakeup placement consider uclamp= restrictions") Reviewed-by: Vincent Guittot Reviewed-by: Dietmar Eggemann Signed-off-by: Qais Yousef (Google) --- kernel/sched/fair.c | 11 +++++------ 1 file changed, 5 insertions(+), 6 deletions(-) diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index c893721ff5b1..3a0a28a0b9c7 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -7695,11 +7695,10 @@ static int find_energy_efficient_cpu(struct task_st= ruct *p, int prev_cpu) for (; pd; pd =3D pd->next) { unsigned long util_min =3D p_util_min, util_max =3D p_util_max; unsigned long cpu_cap, cpu_thermal_cap, util; - unsigned long cur_delta, max_spare_cap =3D 0; + long prev_spare_cap =3D -1, max_spare_cap =3D -1; unsigned long rq_util_min, rq_util_max; - unsigned long prev_spare_cap =3D 0; + unsigned long cur_delta, base_energy; int max_spare_cap_cpu =3D -1; - unsigned long base_energy; int fits, max_fits =3D -1; =20 cpumask_and(cpus, perf_domain_span(pd), cpu_online_mask); @@ -7762,7 +7761,7 @@ static int find_energy_efficient_cpu(struct task_stru= ct *p, int prev_cpu) prev_spare_cap =3D cpu_cap; prev_fits =3D fits; } else if ((fits > max_fits) || - ((fits =3D=3D max_fits) && (cpu_cap > max_spare_cap))) { + ((fits =3D=3D max_fits) && ((long)cpu_cap > max_spare_cap))) { /* * Find the CPU with the maximum spare capacity * among the remaining CPUs in the performance @@ -7774,7 +7773,7 @@ static int find_energy_efficient_cpu(struct task_stru= ct *p, int prev_cpu) } } =20 - if (max_spare_cap_cpu < 0 && prev_spare_cap =3D=3D 0) + if (max_spare_cap_cpu < 0 && prev_spare_cap < 0) continue; =20 eenv_pd_busy_time(&eenv, cpus, p); @@ -7782,7 +7781,7 @@ static int find_energy_efficient_cpu(struct task_stru= ct *p, int prev_cpu) base_energy =3D compute_energy(&eenv, pd, cpus, p, -1); =20 /* Evaluate the energy impact of using prev_cpu. */ - if (prev_spare_cap > 0) { + if (prev_spare_cap > -1) { prev_delta =3D compute_energy(&eenv, pd, cpus, p, prev_cpu); /* CPU utilization has changed */ --=20 2.34.1