From mboxrd@z Thu Jan 1 00:00:00 1970 From: Juri Lelli Subject: Re: [RFC PATCH] sched/cpufreq/schedutil: handling urgent frequency requests Date: Wed, 9 May 2018 08:45:30 +0200 Message-ID: <20180509064530.GA1681@localhost.localdomain> References: <1525704215-8683-1-git-send-email-claudio@evidence.eu.com> <20180508065435.bcht6dyb3rpp6gk5@vireshk-i7> <20180509045425.GA158882@joelaf.mtv.corp.google.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: <20180509045425.GA158882@joelaf.mtv.corp.google.com> Sender: linux-kernel-owner@vger.kernel.org To: Joel Fernandes 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 List-Id: linux-pm@vger.kernel.org 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? Best, - Juri