Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S965106AbbGVN20 (ORCPT ); Wed, 22 Jul 2015 09:28:26 -0400 Received: from foss.arm.com ([217.140.101.70]:35926 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932702AbbGVN2O (ORCPT ); Wed, 22 Jul 2015 09:28:14 -0400 Date: Wed, 22 Jul 2015 14:31:04 +0100 From: Morten Rasmussen To: Leo Yan Cc: peterz@infradead.org, mingo@redhat.com, vincent.guittot@linaro.org, daniel.lezcano@linaro.org, Dietmar Eggemann , yuyang.du@intel.com, mturquette@baylibre.com, rjw@rjwysocki.net, Juri Lelli , sgurrappadi@nvidia.com, pang.xunlei@zte.com.cn, linux-kernel@vger.kernel.org, linux-pm@vger.kernel.org, Russell King Subject: Re: [RFCv5, 01/46] arm: Frequency invariant scheduler load-tracking support Message-ID: <20150722133103.GA21785@e105550-lin.cambridge.arm.com> References: <1436293469-25707-2-git-send-email-morten.rasmussen@arm.com> <20150721154145.GA23852@leoy-linaro> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20150721154145.GA23852@leoy-linaro> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 5585 Lines: 156 On Tue, Jul 21, 2015 at 11:41:45PM +0800, Leo Yan wrote: > Hi Morten, > > On Tue, Jul 07, 2015 at 07:23:44PM +0100, Morten Rasmussen wrote: > > From: Morten Rasmussen > > > > Implements arch-specific function to provide the scheduler with a > > frequency scaling correction factor for more accurate load-tracking. > > The factor is: > > > > current_freq(cpu) << SCHED_CAPACITY_SHIFT / max_freq(cpu) > > > > This implementation only provides frequency invariance. No cpu > > invariance yet. > > > > Cc: Russell King > > > > Signed-off-by: Morten Rasmussen > > > > --- > > arch/arm/include/asm/topology.h | 7 +++++ > > arch/arm/kernel/smp.c | 57 +++++++++++++++++++++++++++++++++++++++-- > > arch/arm/kernel/topology.c | 17 ++++++++++++ > > 3 files changed, 79 insertions(+), 2 deletions(-) > > > > diff --git a/arch/arm/include/asm/topology.h b/arch/arm/include/asm/topology.h > > index 370f7a7..c31096f 100644 > > --- a/arch/arm/include/asm/topology.h > > +++ b/arch/arm/include/asm/topology.h > > @@ -24,6 +24,13 @@ void init_cpu_topology(void); > > void store_cpu_topology(unsigned int cpuid); > > const struct cpumask *cpu_coregroup_mask(int cpu); > > > > +#define arch_scale_freq_capacity arm_arch_scale_freq_capacity > > +struct sched_domain; > > +extern > > +unsigned long arm_arch_scale_freq_capacity(struct sched_domain *sd, int cpu); > > + > > +DECLARE_PER_CPU(atomic_long_t, cpu_freq_capacity); > > + > > #else > > > > static inline void init_cpu_topology(void) { } > > diff --git a/arch/arm/kernel/smp.c b/arch/arm/kernel/smp.c > > index cca5b87..a32539c 100644 > > --- a/arch/arm/kernel/smp.c > > +++ b/arch/arm/kernel/smp.c > > @@ -677,12 +677,34 @@ static DEFINE_PER_CPU(unsigned long, l_p_j_ref); > > static DEFINE_PER_CPU(unsigned long, l_p_j_ref_freq); > > static unsigned long global_l_p_j_ref; > > static unsigned long global_l_p_j_ref_freq; > > +static DEFINE_PER_CPU(atomic_long_t, cpu_max_freq); > > +DEFINE_PER_CPU(atomic_long_t, cpu_freq_capacity); > > + > > +/* > > + * Scheduler load-tracking scale-invariance > > + * > > + * Provides the scheduler with a scale-invariance correction factor that > > + * compensates for frequency scaling through arch_scale_freq_capacity() > > + * (implemented in topology.c). > > + */ > > +static inline > > +void scale_freq_capacity(int cpu, unsigned long curr, unsigned long max) > > +{ > > + unsigned long capacity; > > + > > + if (!max) > > + return; > > + > > + capacity = (curr << SCHED_CAPACITY_SHIFT) / max; > > + atomic_long_set(&per_cpu(cpu_freq_capacity, cpu), capacity); > > +} > > > > static int cpufreq_callback(struct notifier_block *nb, > > unsigned long val, void *data) > > { > > struct cpufreq_freqs *freq = data; > > int cpu = freq->cpu; > > + unsigned long max = atomic_long_read(&per_cpu(cpu_max_freq, cpu)); > > > > if (freq->flags & CPUFREQ_CONST_LOOPS) > > return NOTIFY_OK; > > @@ -707,6 +729,10 @@ static int cpufreq_callback(struct notifier_block *nb, > > per_cpu(l_p_j_ref_freq, cpu), > > freq->new); > > } > > + > > + if (val == CPUFREQ_PRECHANGE) > > + scale_freq_capacity(cpu, freq->new, max); > > + > > return NOTIFY_OK; > > } > > > > @@ -714,11 +740,38 @@ static struct notifier_block cpufreq_notifier = { > > .notifier_call = cpufreq_callback, > > }; > > > > +static int cpufreq_policy_callback(struct notifier_block *nb, > > + unsigned long val, void *data) > > +{ > > + struct cpufreq_policy *policy = data; > > + int i; > > + > > + if (val != CPUFREQ_NOTIFY) > > + return NOTIFY_OK; > > + > > + for_each_cpu(i, policy->cpus) { > > + scale_freq_capacity(i, policy->cur, policy->max); > > + atomic_long_set(&per_cpu(cpu_max_freq, i), policy->max); > > + } > > + > > + return NOTIFY_OK; > > +} > > + > > +static struct notifier_block cpufreq_policy_notifier = { > > + .notifier_call = cpufreq_policy_callback, > > +}; > > + > > static int __init register_cpufreq_notifier(void) > > { > > - return cpufreq_register_notifier(&cpufreq_notifier, > > + int ret; > > + > > + ret = cpufreq_register_notifier(&cpufreq_notifier, > > CPUFREQ_TRANSITION_NOTIFIER); > > + if (ret) > > + return ret; > > + > > + return cpufreq_register_notifier(&cpufreq_policy_notifier, > > + CPUFREQ_POLICY_NOTIFIER); > > } > > core_initcall(register_cpufreq_notifier); > > For "cpu_freq_capacity" structure, could move it into driver/cpufreq > so that it can be shared by all architectures? Otherwise, every > architecture's smp.c need register notifier for themselves. We could, but I put it in arch/arm/* as not all architectures might want this notifier. The frequency scaling factor could be provided based on architecture specific performance counters instead. AFAIK, the Intel p-state driver does not even fire the notifiers so the notifier solution would be redundant code for those platforms. That said, the above solution is not handling changes to policy->max very well. Basically, we don't inform the scheduler if it has changed which means that the OPP represented by "100%" might change. We need cpufreq to keep track of the true max frequency when policy->max is changed to work out the correct scaling factor instead of having it relative to policy->max. Morten -- 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/