From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753861AbbGJJuE (ORCPT ); Fri, 10 Jul 2015 05:50:04 -0400 Received: from eu-smtp-delivery-143.mimecast.com ([207.82.80.143]:7074 "EHLO eu-smtp-delivery-143.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752586AbbGJJuB convert rfc822-to-8bit (ORCPT ); Fri, 10 Jul 2015 05:50:01 -0400 Message-ID: <559F9554.1080400@arm.com> Date: Fri, 10 Jul 2015 10:50:12 +0100 From: Juri Lelli User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.7.0 MIME-Version: 1.0 To: Michael Turquette , Morten Rasmussen , "peterz@infradead.org" , "mingo@redhat.com" CC: "vincent.guittot@linaro.org" , "daniel.lezcano@linaro.org" , Dietmar Eggemann , "yuyang.du@intel.com" , "rjw@rjwysocki.net" , "sgurrappadi@nvidia.com" , "pang.xunlei@zte.com.cn" , "linux-kernel@vger.kernel.org" , "linux-pm@vger.kernel.org" Subject: Re: [RFCv5 PATCH 39/46] sched/cpufreq_sched: use static key for cpu frequency selection References: <1436293469-25707-1-git-send-email-morten.rasmussen@arm.com> <1436293469-25707-40-git-send-email-morten.rasmussen@arm.com> <20150708151956.9112.52403@quantum> In-Reply-To: <20150708151956.9112.52403@quantum> X-OriginalArrivalTime: 10 Jul 2015 09:49:56.0855 (UTC) FILETIME=[C7617070:01D0BAF5] X-MC-Unique: WFTuT3xMS4SsbwwCOW0t0Q-1 Content-Type: text/plain; charset=WINDOWS-1252 Content-Transfer-Encoding: 8BIT Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Mike, On 08/07/15 16:19, Michael Turquette wrote: > Quoting Morten Rasmussen (2015-07-07 11:24:22) >> From: Juri Lelli >> >> Introduce a static key to only affect scheduler hot paths when sched >> governor is enabled. >> >> cc: Ingo Molnar >> cc: Peter Zijlstra >> >> Signed-off-by: Juri Lelli >> --- >> kernel/sched/cpufreq_sched.c | 14 ++++++++++++++ >> kernel/sched/fair.c | 1 + >> kernel/sched/sched.h | 6 ++++++ >> 3 files changed, 21 insertions(+) >> >> diff --git a/kernel/sched/cpufreq_sched.c b/kernel/sched/cpufreq_sched.c >> index 5020f24..2968f3a 100644 >> --- a/kernel/sched/cpufreq_sched.c >> +++ b/kernel/sched/cpufreq_sched.c >> @@ -203,6 +203,18 @@ void cpufreq_sched_set_cap(int cpu, unsigned long capacity) >> return; >> } >> >> +static inline void set_sched_energy_freq(void) >> +{ >> + if (!sched_energy_freq()) >> + static_key_slow_inc(&__sched_energy_freq); >> +} >> + >> +static inline void clear_sched_energy_freq(void) >> +{ >> + if (sched_energy_freq()) >> + static_key_slow_dec(&__sched_energy_freq); >> +} >> + >> static int cpufreq_sched_start(struct cpufreq_policy *policy) >> { >> struct gov_data *gd; >> @@ -243,6 +255,7 @@ static int cpufreq_sched_start(struct cpufreq_policy *policy) >> >> policy->governor_data = gd; >> gd->policy = policy; >> + set_sched_energy_freq(); >> return 0; >> >> err: >> @@ -254,6 +267,7 @@ static int cpufreq_sched_stop(struct cpufreq_policy *policy) >> { >> struct gov_data *gd = policy->governor_data; >> >> + clear_sched_energy_freq(); > > > > These controls are exposed to userspace via cpufreq sysfs knobs. Should > we use a struct static_key_deferred and static_key_slow_dec_deferred() > instead? This helps avoid a possible attack vector for slowing down the > system. > > > > I don't really know what a sane default rate limit would be in that case > though. I guess we could go with HZ, as it seems to be the common default. > Otherwise feel free to add: > > Reviewed-by: Michael Turquette > Thanks, - Juri > Regards, > Mike > >> if (cpufreq_driver_might_sleep()) { >> kthread_stop(gd->task); >> } >> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c >> index f7cb6c9..d395bc9 100644 >> --- a/kernel/sched/fair.c >> +++ b/kernel/sched/fair.c >> @@ -4282,6 +4282,7 @@ static inline void hrtick_update(struct rq *rq) >> #endif >> >> static bool cpu_overutilized(int cpu); >> +struct static_key __sched_energy_freq __read_mostly = STATIC_KEY_INIT_FALSE; >> >> /* >> * The enqueue_task method is called before nr_running is >> diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h >> index 30aa0c4..b5e27d9 100644 >> --- a/kernel/sched/sched.h >> +++ b/kernel/sched/sched.h >> @@ -1476,6 +1476,12 @@ unsigned long arch_scale_cpu_capacity(struct sched_domain *sd, int cpu) >> } >> #endif >> >> +extern struct static_key __sched_energy_freq; >> +static inline bool sched_energy_freq(void) >> +{ >> + return static_key_false(&__sched_energy_freq); >> +} >> + >> #ifdef CONFIG_CPU_FREQ_GOV_SCHED >> void cpufreq_sched_set_cap(int cpu, unsigned long util); >> #else >> -- >> 1.9.1 >> >> -- >> To unsubscribe from this list: send the line "unsubscribe linux-kernel" in >> the body of a message to majordomo@vger.kernel.org >> More majordomo info at http://vger.kernel.org/majordomo-info.html >> Please read the FAQ at http://www.tux.org/lkml/ >