From patchwork Sun Aug 20 21:06:37 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Qais Yousef X-Patchwork-Id: 715633 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 1777CEE49AF for ; Sun, 20 Aug 2023 21:08:23 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231893AbjHTVIT (ORCPT ); Sun, 20 Aug 2023 17:08:19 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:41456 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230169AbjHTVIS (ORCPT ); Sun, 20 Aug 2023 17:08:18 -0400 Received: from mail-wr1-x42e.google.com (mail-wr1-x42e.google.com [IPv6:2a00:1450:4864:20::42e]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 71A384222 for ; Sun, 20 Aug 2023 14:08:05 -0700 (PDT) Received: by mail-wr1-x42e.google.com with SMTP id ffacd0b85a97d-31c5a2e8501so8614f8f.0 for ; Sun, 20 Aug 2023 14:08:05 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=layalina-io.20221208.gappssmtp.com; s=20221208; t=1692565684; x=1693170484; 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=c6qFJPzVrYvXdJFLmkCCK0atIYbjN/54u4wyc75/JBA=; b=HgG+fO1k7dm+jpnKvEM5X5dUvf//duLry6vdxj39GAjwCvPChkZJ8V6NrPGsycssq6 WBi4ahdeVIDEBq2LPdZCZKF8GX++0qJ/OwIiqTxyaKrRo9r4fCKc6TP36YZkImJBVoEJ dJz1P3os9ETaqjObgP/XD7xDMyZrScTkZQVQauNzJ8oDELiqWLY07ADiEQ46vCr1fb87 L/vQ0U8ue4POOVJwDdSSXO/LxX5frec8MHiD8zyKEak7BWWiBFy3X+dKxCBAI8TQCiRl DrdistocMSk3YQbjmIpESR5eLSXLmon5CDzSxue3x4M0klKy2wzg+Yp17lhADIZVFX8u X32w== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20221208; t=1692565684; x=1693170484; 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=c6qFJPzVrYvXdJFLmkCCK0atIYbjN/54u4wyc75/JBA=; b=UnpykcFJucGtCLmxowbzqez4zL/dKnwagOt7Bl6426XoDi5qVxsOmH/ZBcRo17698M JbUJ62DAACiXWdyL/LAc67cRRNSl/IbizlmPVUcRQFkPOaCaaj8MFHCWzgLVwaXEDDa1 EdD834/TBGhN0LBMcelC4mLZ9/pGaincaTUnaOBc12xP/udAMKSp6m4V2CweadOltV1u FhRS4PmiVD1bmnkZRVua1HDA/ZbbUCt4lbhhgXWZEZ1snpDrj89IQCPZVfQIF2ldApMp d/YR2o826Qzq4tS6irvVDoZmZHSRqS+LpRw8hpPE+ccZuFIgTzQhp9+IR4N7LK76pLSP 3w9A== X-Gm-Message-State: AOJu0YwzIPl+lIKbUEwu8Llqk39X7iHJNbNcLNYztKfscHm/OGNvaHnt wP9mdMAOlyoBH5T/JSFrVKX4LA== X-Google-Smtp-Source: AGHT+IGTizLO4t/BYhWwB0zqwdQLDBDyphgkRD7gCuJ1OhbkmLiRC3MOreod/y3MppTTTWxtqnCK6g== X-Received: by 2002:a5d:4fc6:0:b0:319:5e0d:9b0f with SMTP id h6-20020a5d4fc6000000b003195e0d9b0fmr3356883wrw.33.1692565684026; Sun, 20 Aug 2023 14:08:04 -0700 (PDT) Received: from airbuntu.. (host109-151-228-137.range109-151.btcentralplus.com. [109.151.228.137]) by smtp.gmail.com with ESMTPSA id j6-20020adfea46000000b003197a4b0f68sm10336800wrn.7.2023.08.20.14.08.03 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sun, 20 Aug 2023 14:08:03 -0700 (PDT) From: Qais Yousef To: "Rafael J. Wysocki" , Viresh Kumar , Ingo Molnar , Peter Zijlstra Cc: linux-kernel@vger.kernel.org, linux-pm@vger.kernel.org, Vincent Guittot , Dietmar Eggemann , Lukasz Luba , Qais Yousef Subject: [PATCH 1/4] sched: cpufreq: Rename map_util_perf to apply_dvfs_headroom Date: Sun, 20 Aug 2023 22:06:37 +0100 Message-Id: <20230820210640.585311-2-qyousef@layalina.io> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20230820210640.585311-1-qyousef@layalina.io> References: <20230820210640.585311-1-qyousef@layalina.io> MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-pm@vger.kernel.org We are providing headroom for the utilization to grow until the next decision point to pick the next frequency. Give the function a better name and give it some documentation. It is not really mapping anything. Provide a dummy definition for !CONFIG_CPUFREQ which will be required for later patches. Signed-off-by: Qais Yousef (Google) --- include/linux/energy_model.h | 2 +- include/linux/sched/cpufreq.h | 27 ++++++++++++++++++++++++++- kernel/sched/cpufreq_schedutil.c | 6 +++--- 3 files changed, 30 insertions(+), 5 deletions(-) diff --git a/include/linux/energy_model.h b/include/linux/energy_model.h index b9caa01dfac4..6ebde4e69e98 100644 --- a/include/linux/energy_model.h +++ b/include/linux/energy_model.h @@ -243,7 +243,7 @@ static inline unsigned long em_cpu_energy(struct em_perf_domain *pd, scale_cpu = arch_scale_cpu_capacity(cpu); ps = &pd->table[pd->nr_perf_states - 1]; - max_util = map_util_perf(max_util); + max_util = apply_dvfs_headroom(max_util); max_util = min(max_util, allowed_cpu_cap); freq = map_util_freq(max_util, ps->frequency, scale_cpu); diff --git a/include/linux/sched/cpufreq.h b/include/linux/sched/cpufreq.h index bdd31ab93bc5..f0069b354ac8 100644 --- a/include/linux/sched/cpufreq.h +++ b/include/linux/sched/cpufreq.h @@ -29,10 +29,35 @@ static inline unsigned long map_util_freq(unsigned long util, return freq * util / cap; } -static inline unsigned long map_util_perf(unsigned long util) +/* + * DVFS decision are made at discrete points. If CPU stays busy, the util will + * continue to grow, which means it could need to run at a higher frequency + * before the next decision point was reached. IOW, we can't follow the util as + * it grows immediately, but there's a delay before we issue a request to go to + * higher frequency. The headroom caters for this delay so the system continues + * to run at adequate performance point. + * + * This function provides enough headroom to provide adequate performance + * assuming the CPU continues to be busy. + * + * At the moment it is a constant multiplication with 1.25. + * + * TODO: The headroom should be a function of the delay. 25% is too high + * especially on powerful systems. For example, if the delay is 500us, it makes + * more sense to give a small headroom as the next decision point is not far + * away and will follow the util if it continues to rise. On the other hand if + * the delay is 10ms, then we need a bigger headroom so the CPU won't struggle + * at a lower frequency if it never goes to idle until then. + */ +static inline unsigned long apply_dvfs_headroom(unsigned long util) { return util + (util >> 2); } +#else +static inline unsigned long apply_dvfs_headroom(unsigned long util) +{ + return util; +} #endif /* CONFIG_CPU_FREQ */ #endif /* _LINUX_SCHED_CPUFREQ_H */ diff --git a/kernel/sched/cpufreq_schedutil.c b/kernel/sched/cpufreq_schedutil.c index 4492608b7d7f..916c4d3d6192 100644 --- a/kernel/sched/cpufreq_schedutil.c +++ b/kernel/sched/cpufreq_schedutil.c @@ -143,7 +143,7 @@ static unsigned int get_next_freq(struct sugov_policy *sg_policy, unsigned int freq = arch_scale_freq_invariant() ? policy->cpuinfo.max_freq : policy->cur; - util = map_util_perf(util); + util = apply_dvfs_headroom(util); freq = map_util_freq(util, freq, max); if (freq == sg_policy->cached_raw_freq && !sg_policy->need_freq_update) @@ -406,8 +406,8 @@ static void sugov_update_single_perf(struct update_util_data *hook, u64 time, sugov_cpu_is_busy(sg_cpu) && sg_cpu->util < prev_util) sg_cpu->util = prev_util; - cpufreq_driver_adjust_perf(sg_cpu->cpu, map_util_perf(sg_cpu->bw_dl), - map_util_perf(sg_cpu->util), max_cap); + cpufreq_driver_adjust_perf(sg_cpu->cpu, apply_dvfs_headroom(sg_cpu->bw_dl), + apply_dvfs_headroom(sg_cpu->util), max_cap); sg_cpu->sg_policy->last_freq_update_time = time; }