From mboxrd@z Thu Jan 1 00:00:00 1970 From: douglas.raillard@arm.com Subject: [RFC PATCH 7/7] sched/cpufreq: Boost schedutil frequency ramp up Date: Wed, 8 May 2019 18:43:01 +0100 Message-ID: <20190508174301.4828-8-douglas.raillard@arm.com> References: <20190508174301.4828-1-douglas.raillard@arm.com> Mime-Version: 1.0 Content-Transfer-Encoding: 8bit Return-path: In-Reply-To: <20190508174301.4828-1-douglas.raillard@arm.com> Sender: linux-kernel-owner@vger.kernel.org To: linux-kernel@vger.kernel.org Cc: linux-pm@vger.kernel.org, mingo@redhat.com, peterz@infradead.org, quentin.perret@arm.com, douglas.raillard@arm.com, patrick.bellasi@arm.com, dietmar.eggemann@arm.com List-Id: linux-pm@vger.kernel.org From: Douglas RAILLARD In some situations, it can be interesting to spend temporarily more power if that can give a useful frequency boost. The sugov_cpu_is_busy() heuristic is reused to check if there has been some idle time on all CPUs in the considered perf domain since last call to schedutil's get_next_freq(). If not, it is assumed that at least one CPU is in a frequency ramp up phase and the domain will be allowed to spend extra power to reach a stable OPP in a shorter amount of time. Since the extra power expenditure is bounded, it cannot skyrocket even on platforms with a large number of cores in the same frequency domain and/or very high ratio between lowest and highest OPP cost. Signed-off-by: Douglas RAILLARD --- kernel/sched/cpufreq_schedutil.c | 22 +++++++++++++++++----- 1 file changed, 17 insertions(+), 5 deletions(-) diff --git a/kernel/sched/cpufreq_schedutil.c b/kernel/sched/cpufreq_schedutil.c index ce4b90cafbb5..513b32bf14c5 100644 --- a/kernel/sched/cpufreq_schedutil.c +++ b/kernel/sched/cpufreq_schedutil.c @@ -218,6 +218,8 @@ static void sugov_cpu_is_busy_update(struct sugov_cpu *sg_cpu * @sg_policy: schedutil policy object to compute the new frequency for. * @util: Current CPU utilization. * @max: CPU capacity. + * @busy: true if at least one CPU in the policy is busy, which means it had no + * idle time since its last frequency change. * * If the utilization is frequency-invariant, choose the new frequency to be * proportional to it, that is @@ -231,20 +233,28 @@ static void sugov_cpu_is_busy_update(struct sugov_cpu *sg_cpu * * Take C = 1.25 for the frequency tipping point at (util / max) = 0.8. * + * An energy-aware boost is then applied if busy is true. The boost will allow + * selecting frequencies at most twice as costly in term of energy. + * * The lowest driver-supported frequency which is equal or greater than the raw * next_freq (as calculated above) is returned, subject to policy min/max and * cpufreq driver limitations. */ static unsigned int get_next_freq(struct sugov_policy *sg_policy, - unsigned long util, unsigned long max) + unsigned long util, unsigned long max, + bool busy) { struct cpufreq_policy *policy = sg_policy->policy; unsigned int freq = arch_scale_freq_invariant() ? policy->cpuinfo.max_freq : policy->cur; struct em_perf_domain *pd = sugov_policy_get_pd(sg_policy); - /* Maximum power we are ready to spend. */ - unsigned int cost_margin = 0; + /* + * Maximum power we are ready to spend. + * When one CPU is busy in the policy, we apply a boost to help it reach + * the needed frequency faster. + */ + unsigned int cost_margin = busy ? 1024/2 : 0; freq = map_util_freq(util, freq, max); @@ -534,7 +544,7 @@ static void sugov_update_single(struct update_util_data *hook, u64 time, sugov_cpu_is_busy_update(sg_cpu, util); max = sg_cpu->max; util = sugov_iowait_apply(sg_cpu, time, util, max); - next_f = get_next_freq(sg_policy, util, max); + next_f = get_next_freq(sg_policy, util, max, busy); /* * Do not reduce the frequency if the CPU has not been idle * recently, as the reduction is likely to be premature then. @@ -567,6 +577,7 @@ static unsigned int sugov_next_freq_shared(struct sugov_cpu *sg_cpu, u64 time) unsigned long util = 0, max = 1; unsigned int j; unsigned long sg_cpu_util = 0; + bool busy = false; for_each_cpu(j, policy->cpus) { struct sugov_cpu *j_sg_cpu = &per_cpu(sugov_cpu, j); @@ -577,6 +588,7 @@ static unsigned int sugov_next_freq_shared(struct sugov_cpu *sg_cpu, u64 time) sg_cpu_util = j_util; j_max = j_sg_cpu->max; j_util = sugov_iowait_apply(j_sg_cpu, time, j_util, j_max); + busy |= sugov_cpu_is_busy(j_sg_cpu); if (j_util * max > j_max * util) { util = j_util; @@ -592,7 +604,7 @@ static unsigned int sugov_next_freq_shared(struct sugov_cpu *sg_cpu, u64 time) */ sugov_cpu_is_busy_update(sg_cpu, sg_cpu_util); - return get_next_freq(sg_policy, util, max); + return get_next_freq(sg_policy, util, max, busy); } static void -- 2.21.0 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=-9.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,USER_AGENT_GIT autolearn=unavailable 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 0459CC04AAD for ; Wed, 8 May 2019 17:43:28 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id D759D21734 for ; Wed, 8 May 2019 17:43:27 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729132AbfEHRnV (ORCPT ); Wed, 8 May 2019 13:43:21 -0400 Received: from usa-sjc-mx-foss1.foss.arm.com ([217.140.101.70]:41840 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729122AbfEHRnV (ORCPT ); Wed, 8 May 2019 13:43:21 -0400 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.72.51.249]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 8D6C0A78; Wed, 8 May 2019 10:43:20 -0700 (PDT) Received: from e107049-lin.arm.com (e107049-lin.cambridge.arm.com [10.1.195.43]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPA id 138AB3F575; Wed, 8 May 2019 10:43:18 -0700 (PDT) From: douglas.raillard@arm.com To: linux-kernel@vger.kernel.org Cc: linux-pm@vger.kernel.org, mingo@redhat.com, peterz@infradead.org, quentin.perret@arm.com, douglas.raillard@arm.com, patrick.bellasi@arm.com, dietmar.eggemann@arm.com Subject: [RFC PATCH 7/7] sched/cpufreq: Boost schedutil frequency ramp up Date: Wed, 8 May 2019 18:43:01 +0100 Message-Id: <20190508174301.4828-8-douglas.raillard@arm.com> X-Mailer: git-send-email 2.21.0 In-Reply-To: <20190508174301.4828-1-douglas.raillard@arm.com> References: <20190508174301.4828-1-douglas.raillard@arm.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Sender: linux-pm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-pm@vger.kernel.org Content-Type: text/plain; charset="UTF-8" Message-ID: <20190508174301.dqVrmzDaACMQGj3zgfJacVrDQQ1oExcoGc7GgnkZsSc@z> From: Douglas RAILLARD In some situations, it can be interesting to spend temporarily more power if that can give a useful frequency boost. The sugov_cpu_is_busy() heuristic is reused to check if there has been some idle time on all CPUs in the considered perf domain since last call to schedutil's get_next_freq(). If not, it is assumed that at least one CPU is in a frequency ramp up phase and the domain will be allowed to spend extra power to reach a stable OPP in a shorter amount of time. Since the extra power expenditure is bounded, it cannot skyrocket even on platforms with a large number of cores in the same frequency domain and/or very high ratio between lowest and highest OPP cost. Signed-off-by: Douglas RAILLARD --- kernel/sched/cpufreq_schedutil.c | 22 +++++++++++++++++----- 1 file changed, 17 insertions(+), 5 deletions(-) diff --git a/kernel/sched/cpufreq_schedutil.c b/kernel/sched/cpufreq_schedutil.c index ce4b90cafbb5..513b32bf14c5 100644 --- a/kernel/sched/cpufreq_schedutil.c +++ b/kernel/sched/cpufreq_schedutil.c @@ -218,6 +218,8 @@ static void sugov_cpu_is_busy_update(struct sugov_cpu *sg_cpu * @sg_policy: schedutil policy object to compute the new frequency for. * @util: Current CPU utilization. * @max: CPU capacity. + * @busy: true if at least one CPU in the policy is busy, which means it had no + * idle time since its last frequency change. * * If the utilization is frequency-invariant, choose the new frequency to be * proportional to it, that is @@ -231,20 +233,28 @@ static void sugov_cpu_is_busy_update(struct sugov_cpu *sg_cpu * * Take C = 1.25 for the frequency tipping point at (util / max) = 0.8. * + * An energy-aware boost is then applied if busy is true. The boost will allow + * selecting frequencies at most twice as costly in term of energy. + * * The lowest driver-supported frequency which is equal or greater than the raw * next_freq (as calculated above) is returned, subject to policy min/max and * cpufreq driver limitations. */ static unsigned int get_next_freq(struct sugov_policy *sg_policy, - unsigned long util, unsigned long max) + unsigned long util, unsigned long max, + bool busy) { struct cpufreq_policy *policy = sg_policy->policy; unsigned int freq = arch_scale_freq_invariant() ? policy->cpuinfo.max_freq : policy->cur; struct em_perf_domain *pd = sugov_policy_get_pd(sg_policy); - /* Maximum power we are ready to spend. */ - unsigned int cost_margin = 0; + /* + * Maximum power we are ready to spend. + * When one CPU is busy in the policy, we apply a boost to help it reach + * the needed frequency faster. + */ + unsigned int cost_margin = busy ? 1024/2 : 0; freq = map_util_freq(util, freq, max); @@ -534,7 +544,7 @@ static void sugov_update_single(struct update_util_data *hook, u64 time, sugov_cpu_is_busy_update(sg_cpu, util); max = sg_cpu->max; util = sugov_iowait_apply(sg_cpu, time, util, max); - next_f = get_next_freq(sg_policy, util, max); + next_f = get_next_freq(sg_policy, util, max, busy); /* * Do not reduce the frequency if the CPU has not been idle * recently, as the reduction is likely to be premature then. @@ -567,6 +577,7 @@ static unsigned int sugov_next_freq_shared(struct sugov_cpu *sg_cpu, u64 time) unsigned long util = 0, max = 1; unsigned int j; unsigned long sg_cpu_util = 0; + bool busy = false; for_each_cpu(j, policy->cpus) { struct sugov_cpu *j_sg_cpu = &per_cpu(sugov_cpu, j); @@ -577,6 +588,7 @@ static unsigned int sugov_next_freq_shared(struct sugov_cpu *sg_cpu, u64 time) sg_cpu_util = j_util; j_max = j_sg_cpu->max; j_util = sugov_iowait_apply(j_sg_cpu, time, j_util, j_max); + busy |= sugov_cpu_is_busy(j_sg_cpu); if (j_util * max > j_max * util) { util = j_util; @@ -592,7 +604,7 @@ static unsigned int sugov_next_freq_shared(struct sugov_cpu *sg_cpu, u64 time) */ sugov_cpu_is_busy_update(sg_cpu, sg_cpu_util); - return get_next_freq(sg_policy, util, max); + return get_next_freq(sg_policy, util, max, busy); } static void -- 2.21.0