From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756221AbeEIGzW (ORCPT ); Wed, 9 May 2018 02:55:22 -0400 Received: from mail-pl0-f67.google.com ([209.85.160.67]:43181 "EHLO mail-pl0-f67.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756199AbeEIGzS (ORCPT ); Wed, 9 May 2018 02:55:18 -0400 X-Google-Smtp-Source: AB8JxZrvi1gI4iZuvSlo2ooCWPG1BT0wawe2b/XABzmO2gtlFSawOCtD7WikvfU+G4N9RDTcJI9j+g== Date: Tue, 8 May 2018 23:55:16 -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: <20180509065516.GA52784@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-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20180509064530.GA1681@localhost.localdomain> User-Agent: Mutt/1.9.2 (2017-12-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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? Yes, I was also thinking the same. I think we can come up with a better mechanism that still doesn't use work_in_progress. I am cooking up a patch but may take a bit longer since I'm traveling. I'll share it once I have something :) thanks, - Joel