From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S964787AbbGHPJy (ORCPT ); Wed, 8 Jul 2015 11:09:54 -0400 Received: from mail-pa0-f54.google.com ([209.85.220.54]:33680 "EHLO mail-pa0-f54.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1758642AbbGHPJt convert rfc822-to-8bit (ORCPT ); Wed, 8 Jul 2015 11:09:49 -0400 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8BIT To: Morten Rasmussen , peterz@infradead.org, mingo@redhat.com From: Michael Turquette In-Reply-To: <1436293469-25707-39-git-send-email-morten.rasmussen@arm.com> Cc: vincent.guittot@linaro.org, daniel.lezcano@linaro.org, "Dietmar Eggemann" , yuyang.du@intel.com, rjw@rjwysocki.net, "Juri Lelli" , sgurrappadi@nvidia.com, pang.xunlei@zte.com.cn, linux-kernel@vger.kernel.org, linux-pm@vger.kernel.org, "Juri Lelli" References: <1436293469-25707-1-git-send-email-morten.rasmussen@arm.com> <1436293469-25707-39-git-send-email-morten.rasmussen@arm.com> Message-ID: <20150708150929.9112.30749@quantum> User-Agent: alot/0.3.5 Subject: Re: [RFCv5 PATCH 38/46] sched: scheduler-driven cpu frequency selection Date: Wed, 08 Jul 2015 08:09:29 -0700 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Quoting Morten Rasmussen (2015-07-07 11:24:21) > From: Michael Turquette > > Scheduler-driven cpu frequency selection is desirable as part of the > on-going effort to make the scheduler better aware of energy > consumption. No piece of the Linux kernel has a better view of the > factors that affect a cpu frequency selection policy than the > scheduler[0], and this patch is an attempt to converge on an initial > solution. > > This patch implements a simple shim layer between the Linux scheduler > and the cpufreq subsystem. This interface accepts a capacity request > from the Completely Fair Scheduler and honors the max request from all > cpus in the same frequency domain. > > The policy magic comes from choosing the cpu capacity request from cfs > and is not contained in this cpufreq governor. This code is > intentionally dumb. > > Note that this "governor" is event-driven. There is no polling loop to > check cpu idle time nor any other method which is unsynchronized with > the scheduler. > > Thanks to Juri Lelli for contributing design ideas, > code and test results. > > [0] http://article.gmane.org/gmane.linux.kernel/1499836 > > Signed-off-by: Michael Turquette > Signed-off-by: Juri Lelli Hi Morten, I believe your sign-off is needed here as well. Regards, Mike > --- > drivers/cpufreq/Kconfig | 24 ++++ > include/linux/cpufreq.h | 3 + > kernel/sched/Makefile | 1 + > kernel/sched/cpufreq_sched.c | 308 +++++++++++++++++++++++++++++++++++++++++++ > kernel/sched/sched.h | 8 ++ > 5 files changed, 344 insertions(+) > create mode 100644 kernel/sched/cpufreq_sched.c > > diff --git a/drivers/cpufreq/Kconfig b/drivers/cpufreq/Kconfig > index 659879a..9bbf44c 100644 > --- a/drivers/cpufreq/Kconfig > +++ b/drivers/cpufreq/Kconfig > @@ -102,6 +102,15 @@ config CPU_FREQ_DEFAULT_GOV_CONSERVATIVE > Be aware that not all cpufreq drivers support the conservative > governor. If unsure have a look at the help section of the > driver. Fallback governor will be the performance governor. > + > +config CPU_FREQ_DEFAULT_GOV_SCHED > + bool "sched" > + select CPU_FREQ_GOV_SCHED > + select CPU_FREQ_GOV_PERFORMANCE > + help > + Use the CPUfreq governor 'sched' as default. This scales > + cpu frequency from the scheduler as per-entity load tracking > + statistics are updated. > endchoice > > config CPU_FREQ_GOV_PERFORMANCE > @@ -183,6 +192,21 @@ config CPU_FREQ_GOV_CONSERVATIVE > > If in doubt, say N. > > +config CPU_FREQ_GOV_SCHED > + tristate "'sched' cpufreq governor" > + depends on CPU_FREQ > + select CPU_FREQ_GOV_COMMON > + help > + 'sched' - this governor scales cpu frequency from the > + scheduler as a function of cpu capacity utilization. It does > + not evaluate utilization on a periodic basis (as ondemand > + does) but instead is invoked from the completely fair > + scheduler when updating per-entity load tracking statistics. > + Latency to respond to changes in load is improved over polling > + governors due to its event-driven design. > + > + If in doubt, say N. > + > comment "CPU frequency scaling drivers" > > config CPUFREQ_DT > diff --git a/include/linux/cpufreq.h b/include/linux/cpufreq.h > index 1f2c9a1..30241c9 100644 > --- a/include/linux/cpufreq.h > +++ b/include/linux/cpufreq.h > @@ -494,6 +494,9 @@ extern struct cpufreq_governor cpufreq_gov_ondemand; > #elif defined(CONFIG_CPU_FREQ_DEFAULT_GOV_CONSERVATIVE) > extern struct cpufreq_governor cpufreq_gov_conservative; > #define CPUFREQ_DEFAULT_GOVERNOR (&cpufreq_gov_conservative) > +#elif defined(CONFIG_CPU_FREQ_DEFAULT_GOV_SCHED_GOV) > +extern struct cpufreq_governor cpufreq_gov_sched_gov; > +#define CPUFREQ_DEFAULT_GOVERNOR (&cpufreq_gov_sched) > #endif > > /********************************************************************* > diff --git a/kernel/sched/Makefile b/kernel/sched/Makefile > index 6768797..90ed832 100644 > --- a/kernel/sched/Makefile > +++ b/kernel/sched/Makefile > @@ -19,3 +19,4 @@ obj-$(CONFIG_SCHED_AUTOGROUP) += auto_group.o > obj-$(CONFIG_SCHEDSTATS) += stats.o > obj-$(CONFIG_SCHED_DEBUG) += debug.o > obj-$(CONFIG_CGROUP_CPUACCT) += cpuacct.o > +obj-$(CONFIG_CPU_FREQ_GOV_SCHED) += cpufreq_sched.o > diff --git a/kernel/sched/cpufreq_sched.c b/kernel/sched/cpufreq_sched.c > new file mode 100644 > index 0000000..5020f24 > --- /dev/null > +++ b/kernel/sched/cpufreq_sched.c > @@ -0,0 +1,308 @@ > +/* > + * Copyright (C) 2015 Michael Turquette > + * > + * This program is free software; you can redistribute it and/or modify > + * it under the terms of the GNU General Public License version 2 as > + * published by the Free Software Foundation. > + */ > + > +#include > +#include > +#include > +#include > +#include > + > +#include "sched.h" > + > +#define THROTTLE_NSEC 50000000 /* 50ms default */ > + > +static DEFINE_PER_CPU(unsigned long, pcpu_capacity); > +static DEFINE_PER_CPU(struct cpufreq_policy *, pcpu_policy); > + > +/** > + * gov_data - per-policy data internal to the governor > + * @throttle: next throttling period expiry. Derived from throttle_nsec > + * @throttle_nsec: throttle period length in nanoseconds > + * @task: worker thread for dvfs transition that may block/sleep > + * @irq_work: callback used to wake up worker thread > + * @freq: new frequency stored in *_sched_update_cpu and used in *_sched_thread > + * > + * struct gov_data is the per-policy cpufreq_sched-specific data structure. A > + * per-policy instance of it is created when the cpufreq_sched governor receives > + * the CPUFREQ_GOV_START condition and a pointer to it exists in the gov_data > + * member of struct cpufreq_policy. > + * > + * Readers of this data must call down_read(policy->rwsem). Writers must > + * call down_write(policy->rwsem). > + */ > +struct gov_data { > + ktime_t throttle; > + unsigned int throttle_nsec; > + struct task_struct *task; > + struct irq_work irq_work; > + struct cpufreq_policy *policy; > + unsigned int freq; > +}; > + > +static void cpufreq_sched_try_driver_target(struct cpufreq_policy *policy, unsigned int freq) > +{ > + struct gov_data *gd = policy->governor_data; > + > + /* avoid race with cpufreq_sched_stop */ > + if (!down_write_trylock(&policy->rwsem)) > + return; > + > + __cpufreq_driver_target(policy, freq, CPUFREQ_RELATION_L); > + > + gd->throttle = ktime_add_ns(ktime_get(), gd->throttle_nsec); > + up_write(&policy->rwsem); > +} > + > +/* > + * we pass in struct cpufreq_policy. This is safe because changing out the > + * policy requires a call to __cpufreq_governor(policy, CPUFREQ_GOV_STOP), > + * which tears down all of the data structures and __cpufreq_governor(policy, > + * CPUFREQ_GOV_START) will do a full rebuild, including this kthread with the > + * new policy pointer > + */ > +static int cpufreq_sched_thread(void *data) > +{ > + struct sched_param param; > + struct cpufreq_policy *policy; > + struct gov_data *gd; > + int ret; > + > + policy = (struct cpufreq_policy *) data; > + if (!policy) { > + pr_warn("%s: missing policy\n", __func__); > + do_exit(-EINVAL); > + } > + > + gd = policy->governor_data; > + if (!gd) { > + pr_warn("%s: missing governor data\n", __func__); > + do_exit(-EINVAL); > + } > + > + param.sched_priority = 50; > + ret = sched_setscheduler_nocheck(gd->task, SCHED_FIFO, ¶m); > + if (ret) { > + pr_warn("%s: failed to set SCHED_FIFO\n", __func__); > + do_exit(-EINVAL); > + } else { > + pr_debug("%s: kthread (%d) set to SCHED_FIFO\n", > + __func__, gd->task->pid); > + } > + > + ret = set_cpus_allowed_ptr(gd->task, policy->related_cpus); > + if (ret) { > + pr_warn("%s: failed to set allowed ptr\n", __func__); > + do_exit(-EINVAL); > + } > + > + /* main loop of the per-policy kthread */ > + do { > + set_current_state(TASK_INTERRUPTIBLE); > + schedule(); > + if (kthread_should_stop()) > + break; > + > + cpufreq_sched_try_driver_target(policy, gd->freq); > + } while (!kthread_should_stop()); > + > + do_exit(0); > +} > + > +static void cpufreq_sched_irq_work(struct irq_work *irq_work) > +{ > + struct gov_data *gd; > + > + gd = container_of(irq_work, struct gov_data, irq_work); > + if (!gd) { > + return; > + } > + > + wake_up_process(gd->task); > +} > + > +/** > + * cpufreq_sched_set_capacity - interface to scheduler for changing capacity values > + * @cpu: cpu whose capacity utilization has recently changed > + * @capacity: the new capacity requested by cpu > + * > + * cpufreq_sched_sched_capacity is an interface exposed to the scheduler so > + * that the scheduler may inform the governor of updates to capacity > + * utilization and make changes to cpu frequency. Currently this interface is > + * designed around PELT values in CFS. It can be expanded to other scheduling > + * classes in the future if needed. > + * > + * cpufreq_sched_set_capacity raises an IPI. The irq_work handler for that IPI > + * wakes up the thread that does the actual work, cpufreq_sched_thread. > + * > + * This functions bails out early if either condition is true: > + * 1) this cpu did not the new maximum capacity for its frequency domain > + * 2) no change in cpu frequency is necessary to meet the new capacity request > + */ > +void cpufreq_sched_set_cap(int cpu, unsigned long capacity) > +{ > + unsigned int freq_new, cpu_tmp; > + struct cpufreq_policy *policy; > + struct gov_data *gd; > + unsigned long capacity_max = 0; > + > + /* update per-cpu capacity request */ > + __this_cpu_write(pcpu_capacity, capacity); > + > + policy = cpufreq_cpu_get(cpu); > + if (IS_ERR_OR_NULL(policy)) { > + return; > + } > + > + if (!policy->governor_data) > + goto out; > + > + gd = policy->governor_data; > + > + /* bail early if we are throttled */ > + if (ktime_before(ktime_get(), gd->throttle)) > + goto out; > + > + /* find max capacity requested by cpus in this policy */ > + for_each_cpu(cpu_tmp, policy->cpus) > + capacity_max = max(capacity_max, per_cpu(pcpu_capacity, cpu_tmp)); > + > + /* > + * We only change frequency if this cpu's capacity request represents a > + * new max. If another cpu has requested a capacity greater than the > + * previous max then we rely on that cpu to hit this code path and make > + * the change. IOW, the cpu with the new max capacity is responsible > + * for setting the new capacity/frequency. > + * > + * If this cpu is not the new maximum then bail > + */ > + if (capacity_max > capacity) > + goto out; > + > + /* Convert the new maximum capacity request into a cpu frequency */ > + freq_new = capacity * policy->max >> SCHED_CAPACITY_SHIFT; > + > + /* No change in frequency? Bail and return current capacity. */ > + if (freq_new == policy->cur) > + goto out; > + > + /* store the new frequency and perform the transition */ > + gd->freq = freq_new; > + > + if (cpufreq_driver_might_sleep()) > + irq_work_queue_on(&gd->irq_work, cpu); > + else > + cpufreq_sched_try_driver_target(policy, freq_new); > + > +out: > + cpufreq_cpu_put(policy); > + return; > +} > + > +static int cpufreq_sched_start(struct cpufreq_policy *policy) > +{ > + struct gov_data *gd; > + int cpu; > + > + /* prepare per-policy private data */ > + gd = kzalloc(sizeof(*gd), GFP_KERNEL); > + if (!gd) { > + pr_debug("%s: failed to allocate private data\n", __func__); > + return -ENOMEM; > + } > + > + /* initialize per-cpu data */ > + for_each_cpu(cpu, policy->cpus) { > + per_cpu(pcpu_capacity, cpu) = 0; > + per_cpu(pcpu_policy, cpu) = policy; > + } > + > + /* > + * Don't ask for freq changes at an higher rate than what > + * the driver advertises as transition latency. > + */ > + gd->throttle_nsec = policy->cpuinfo.transition_latency ? > + policy->cpuinfo.transition_latency : > + THROTTLE_NSEC; > + pr_debug("%s: throttle threshold = %u [ns]\n", > + __func__, gd->throttle_nsec); > + > + if (cpufreq_driver_might_sleep()) { > + /* init per-policy kthread */ > + gd->task = kthread_run(cpufreq_sched_thread, policy, "kcpufreq_sched_task"); > + if (IS_ERR_OR_NULL(gd->task)) { > + pr_err("%s: failed to create kcpufreq_sched_task thread\n", __func__); > + goto err; > + } > + init_irq_work(&gd->irq_work, cpufreq_sched_irq_work); > + } > + > + policy->governor_data = gd; > + gd->policy = policy; > + return 0; > + > +err: > + kfree(gd); > + return -ENOMEM; > +} > + > +static int cpufreq_sched_stop(struct cpufreq_policy *policy) > +{ > + struct gov_data *gd = policy->governor_data; > + > + if (cpufreq_driver_might_sleep()) { > + kthread_stop(gd->task); > + } > + > + policy->governor_data = NULL; > + > + /* FIXME replace with devm counterparts? */ > + kfree(gd); > + return 0; > +} > + > +static int cpufreq_sched_setup(struct cpufreq_policy *policy, unsigned int event) > +{ > + switch (event) { > + case CPUFREQ_GOV_START: > + /* Start managing the frequency */ > + return cpufreq_sched_start(policy); > + > + case CPUFREQ_GOV_STOP: > + return cpufreq_sched_stop(policy); > + > + case CPUFREQ_GOV_LIMITS: /* unused */ > + case CPUFREQ_GOV_POLICY_INIT: /* unused */ > + case CPUFREQ_GOV_POLICY_EXIT: /* unused */ > + break; > + } > + return 0; > +} > + > +#ifndef CONFIG_CPU_FREQ_DEFAULT_GOV_SCHED > +static > +#endif > +struct cpufreq_governor cpufreq_gov_sched = { > + .name = "sched", > + .governor = cpufreq_sched_setup, > + .owner = THIS_MODULE, > +}; > + > +static int __init cpufreq_sched_init(void) > +{ > + return cpufreq_register_governor(&cpufreq_gov_sched); > +} > + > +static void __exit cpufreq_sched_exit(void) > +{ > + cpufreq_unregister_governor(&cpufreq_gov_sched); > +} > + > +/* Try to make this the default governor */ > +fs_initcall(cpufreq_sched_init); > + > +MODULE_LICENSE("GPL v2"); > diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h > index c395559..30aa0c4 100644 > --- a/kernel/sched/sched.h > +++ b/kernel/sched/sched.h > @@ -1476,6 +1476,13 @@ unsigned long arch_scale_cpu_capacity(struct sched_domain *sd, int cpu) > } > #endif > > +#ifdef CONFIG_CPU_FREQ_GOV_SCHED > +void cpufreq_sched_set_cap(int cpu, unsigned long util); > +#else > +static inline void cpufreq_sched_set_cap(int cpu, unsigned long util) > +{ } > +#endif > + > static inline void sched_rt_avg_update(struct rq *rq, u64 rt_delta) > { > rq->rt_avg += rt_delta * arch_scale_freq_capacity(NULL, cpu_of(rq)); > @@ -1484,6 +1491,7 @@ static inline void sched_rt_avg_update(struct rq *rq, u64 rt_delta) > #else > static inline void sched_rt_avg_update(struct rq *rq, u64 rt_delta) { } > static inline void sched_avg_update(struct rq *rq) { } > +static inline void gov_cfs_update_cpu(int cpu) {} > #endif > > extern void start_bandwidth_timer(struct hrtimer *period_timer, ktime_t period); > -- > 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/