From patchwork Wed May 9 08:06:44 2018 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Joel Fernandes X-Patchwork-Id: 10388593 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork.web.codeaurora.org (Postfix) with ESMTP id 40499602C2 for ; Wed, 9 May 2018 08:06:54 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 307D728E18 for ; Wed, 9 May 2018 08:06:54 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 23F2A28E24; Wed, 9 May 2018 08:06:54 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-7.3 required=2.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID, MAILING_LIST_MULTI, RCVD_IN_DNSWL_HI, URG_BIZ autolearn=ham version=3.3.1 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 8686B28E18 for ; Wed, 9 May 2018 08:06:53 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756135AbeEIIGv (ORCPT ); Wed, 9 May 2018 04:06:51 -0400 Received: from mail-pl0-f66.google.com ([209.85.160.66]:39966 "EHLO mail-pl0-f66.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756120AbeEIIGr (ORCPT ); Wed, 9 May 2018 04:06:47 -0400 Received: by mail-pl0-f66.google.com with SMTP id t22-v6so3833125plo.7 for ; Wed, 09 May 2018 01:06:46 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=joelfernandes-org.20150623.gappssmtp.com; s=20150623; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to:user-agent; bh=nSELlwoXbrYW1QsDwi1PZayrCJ2THC4ht6oV9vAkz2Q=; b=1dftfK+vA6fZ8VpZWDu1IxiBVbtPxu8rU0/tLtCC6uk7tfPs4g8rX3PAs3ZSGb2RGa xEeq6hCmpSiZqltefopwGAhjrQURxl/aEwDr/dsyi/UCJ84sWYWARzrIJDCmA6nhxeI2 gFKEch1nkbMZD1XpQ6vu0C8pTa3vtOweCXQ9CcIvxn3qV1FBAMJRQKy8HXgpvU/xebqN m5/y+d1IG/brRDc5yGUjQ+ibj4C9jP+WF4i8z2eBUiKtSFe6LyGsQwH8OGroYN8LLqU7 7Lz4ugbkEYQ4gDGz7IF3pzrZ/WiJ5ppZX0w5Q3J0ngf+Uw7kD+33Q/L8QByc2kDMVoqS YE5g== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to:user-agent; bh=nSELlwoXbrYW1QsDwi1PZayrCJ2THC4ht6oV9vAkz2Q=; b=Gnd8BocnEZg+nXL9dRo3ovnayP0mK1jrEM/JGr4qn6Vbt08XZh0YVVdAjseyC5VFZN lYxxsFvb+5U3T0LPgPagLQxTvexyizGIMvmkG3lQ5NbHjkBnMHZRxlnbApkPVBu2m2ld 02Eohyl6A13Hz3ZuAdTO6iK52QyFkP2CUf6pgag7MGJrKpFe3s1bSiS6hO8U5IusUEZb QzkoRc1Gi8FtzD9+veqNovv1PBVPaT4IY2yaHbtCdt8iwQXlosVSZdSG6xQbLSAYIYzP nUiqiZIzG2NTQn4heCZV5irhJ5UdO+INl4XPqGo+NAg1sAf4lqP3iaVeFaJLtsa1Kjga v7eg== X-Gm-Message-State: ALQs6tANw+S/kQhnHCdRM7Iqnj6Q30v8se981AvuEGGRlbfw4imS5XH1 cWgXDipuy5bIuwiavHX5HzrxF2MCPU8= X-Google-Smtp-Source: AB8JxZokSNv/P+Ybd+hmclidMzBFGj+yb0/7r93dNgCNQnf2A4GqIfPa0ccd2aPbAVJi+854wP8pQw== X-Received: by 2002:a17:902:d909:: with SMTP id c9-v6mr18040466plz.293.1525853205908; Wed, 09 May 2018 01:06:45 -0700 (PDT) Received: from localhost ([2620:0:1000:1600:3122:ea9c:d178:eb]) by smtp.gmail.com with ESMTPSA id i1sm34891436pfi.133.2018.05.09.01.06.45 (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Wed, 09 May 2018 01:06:45 -0700 (PDT) Date: Wed, 9 May 2018 01:06:44 -0700 From: Joel Fernandes To: Juri Lelli Cc: Viresh Kumar , Claudio Scordino , linux-kernel@vger.kernel.org, "Rafael J . Wysocki" , Peter Zijlstra , Ingo Molnar , Patrick Bellasi , Luca Abeni , Joel Fernandes , linux-pm@vger.kernel.org Subject: Re: [RFC PATCH] sched/cpufreq/schedutil: handling urgent frequency requests Message-ID: <20180509080644.GA76874@joelaf.mtv.corp.google.com> References: <1525704215-8683-1-git-send-email-claudio@evidence.eu.com> <20180508065435.bcht6dyb3rpp6gk5@vireshk-i7> <20180509045425.GA158882@joelaf.mtv.corp.google.com> <20180509064530.GA1681@localhost.localdomain> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20180509064530.GA1681@localhost.localdomain> User-Agent: Mutt/1.9.2 (2017-12-15) Sender: linux-pm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-pm@vger.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP On Wed, May 09, 2018 at 08:45:30AM +0200, Juri Lelli wrote: > On 08/05/18 21:54, Joel Fernandes wrote: > > [...] > > > Just for discussion sake, is there any need for work_in_progress? If we can > > queue multiple work say kthread_queue_work can handle it, then just queuing > > works whenever they are available should be Ok and the kthread loop can > > handle them. __cpufreq_driver_target is also protected by the work lock if > > there is any concern that can have races... only thing is rate-limiting of > > the requests, but we are doing a rate limiting, just not for the "DL > > increased utilization" type requests (which I don't think we are doing at the > > moment for urgent DL requests anyway). > > > > Following is an untested diff to show the idea. What do you think? > > > > thanks, > > > > - Joel > > > > ----8<--- > > diff --git a/kernel/sched/cpufreq_schedutil.c b/kernel/sched/cpufreq_schedutil.c > > index d2c6083304b4..862634ff4bf3 100644 > > --- a/kernel/sched/cpufreq_schedutil.c > > +++ b/kernel/sched/cpufreq_schedutil.c > > @@ -38,7 +38,6 @@ struct sugov_policy { > > struct mutex work_lock; > > struct kthread_worker worker; > > struct task_struct *thread; > > - bool work_in_progress; > > > > bool need_freq_update; > > }; > > @@ -92,16 +91,8 @@ static bool sugov_should_update_freq(struct sugov_policy *sg_policy, u64 time) > > !cpufreq_can_do_remote_dvfs(sg_policy->policy)) > > return false; > > > > - if (sg_policy->work_in_progress) > > - return false; > > - > > if (unlikely(sg_policy->need_freq_update)) { > > sg_policy->need_freq_update = false; > > - /* > > - * This happens when limits change, so forget the previous > > - * next_freq value and force an update. > > - */ > > - sg_policy->next_freq = UINT_MAX; > > return true; > > } > > > > @@ -129,7 +120,6 @@ static void sugov_update_commit(struct sugov_policy *sg_policy, u64 time, > > policy->cur = next_freq; > > trace_cpu_frequency(next_freq, smp_processor_id()); > > } else { > > - sg_policy->work_in_progress = true; > > irq_work_queue(&sg_policy->irq_work); > > Isn't this potentially introducing unneeded irq pressure (and doing the > whole wakeup the kthread thing), while the already active kthread could > simply handle multiple back-to-back requests before going to sleep? How about this? Will use the latest request, and also doesn't do unnecessary irq_work_queue: (untested) -----8<-------- diff --git a/kernel/sched/cpufreq_schedutil.c b/kernel/sched/cpufreq_schedutil.c index d2c6083304b4..6a3e42b01f52 100644 --- a/kernel/sched/cpufreq_schedutil.c +++ b/kernel/sched/cpufreq_schedutil.c @@ -38,7 +38,7 @@ struct sugov_policy { struct mutex work_lock; struct kthread_worker worker; struct task_struct *thread; - bool work_in_progress; + bool work_in_progress; /* Has kthread been kicked */ bool need_freq_update; }; @@ -92,9 +92,6 @@ static bool sugov_should_update_freq(struct sugov_policy *sg_policy, u64 time) !cpufreq_can_do_remote_dvfs(sg_policy->policy)) return false; - if (sg_policy->work_in_progress) - return false; - if (unlikely(sg_policy->need_freq_update)) { sg_policy->need_freq_update = false; /* @@ -129,8 +126,11 @@ static void sugov_update_commit(struct sugov_policy *sg_policy, u64 time, policy->cur = next_freq; trace_cpu_frequency(next_freq, smp_processor_id()); } else { - sg_policy->work_in_progress = true; - irq_work_queue(&sg_policy->irq_work); + /* work_in_progress helps us not queue unnecessarily */ + if (!sg_policy->work_in_progress) { + sg_policy->work_in_progress = true; + irq_work_queue(&sg_policy->irq_work); + } } } @@ -381,13 +381,23 @@ sugov_update_shared(struct update_util_data *hook, u64 time, unsigned int flags) static void sugov_work(struct kthread_work *work) { struct sugov_policy *sg_policy = container_of(work, struct sugov_policy, work); + unsigned int freq; + + /* + * Hold sg_policy->update_lock just enough to handle the case where: + * if sg_policy->next_freq is updated before work_in_progress is set to + * false, we may miss queueing the new update request since + * work_in_progress would appear to be true. + */ + raw_spin_lock(&sg_policy->update_lock); + freq = sg_policy->next_freq; + sg_policy->work_in_progress = false; + raw_spin_unlock(&sg_policy->update_lock); mutex_lock(&sg_policy->work_lock); - __cpufreq_driver_target(sg_policy->policy, sg_policy->next_freq, + __cpufreq_driver_target(sg_policy->policy, freq, CPUFREQ_RELATION_L); mutex_unlock(&sg_policy->work_lock); - - sg_policy->work_in_progress = false; } static void sugov_irq_work(struct irq_work *irq_work)