From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by lindbergh.monkeyblade.net (Postfix) with ESMTP id 63BF4F4; Sun, 10 Dec 2023 23:55:08 -0800 (PST) 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 8C14B1007; Sun, 10 Dec 2023 23:55:54 -0800 (PST) Received: from [10.57.84.143] (unknown [10.57.84.143]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 0EC273F5A1; Sun, 10 Dec 2023 23:55:05 -0800 (PST) Message-ID: <8ee6425a-0a0e-4391-9fd3-8fe74c809772@arm.com> Date: Mon, 11 Dec 2023 07:56:09 +0000 Precedence: bulk X-Mailing-List: linux-pm@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 1/4] sched/fair: Be less aggressive in calling cpufreq_update_util() To: Qais Yousef Cc: linux-kernel@vger.kernel.org, Vincent Guittot , Viresh Kumar , "Rafael J. Wysocki" , Dietmar Eggemann , linux-pm@vger.kernel.org, Ingo Molnar , Wei Wang , Rick Yiu , Chung-Kai Mei , Hongyan Xia , Peter Zijlstra References: <20231208015242.385103-1-qyousef@layalina.io> <20231208015242.385103-2-qyousef@layalina.io> <20231210205156.kausxdcwsydggwie@airbuntu> Content-Language: en-US From: Lukasz Luba In-Reply-To: <20231210205156.kausxdcwsydggwie@airbuntu> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 12/10/23 20:51, Qais Yousef wrote: > On 12/08/23 10:05, Lukasz Luba wrote: >> Hi Qais, >> >> On 12/8/23 01:52, Qais Yousef wrote: >> >> [snip] >> >>> @@ -6704,14 +6677,6 @@ enqueue_task_fair(struct rq *rq, struct task_struct *p, int flags) >>> */ >>> util_est_enqueue(&rq->cfs, p); >>> - /* >>> - * If in_iowait is set, the code below may not trigger any cpufreq >>> - * utilization updates, so do it here explicitly with the IOWAIT flag >>> - * passed. >>> - */ >>> - if (p->in_iowait) >>> - cpufreq_update_util(rq, SCHED_CPUFREQ_IOWAIT); >>> - >> >> Why this io wait boost is considered as the $subject says 'aggressive' >> calling? > > This will trigger a frequency update along with the iowait boost. Did I miss > something? Yes, it will change CPU freq and it was the main goal for this code path. We have tests which check how that works on different memory types. Why do you want to remove it? Did you run some tests (e.g. fio, gallery, etc) to check if you still have a decent performance out some new ufs/nvme memories? Beata & Dietmar have presented at LPC2021 a proposal to have a per-task io boost, with a bit more controllable way of the trade off power vs. performance [1]. IMO the io wait boost could evolve, not simply die. Regards, Lukasz [1] https://lpc.events/event/11/contributions/1042/