/* * drivers/cpufreq/cpufreq_governor.c * * CPUFREQ governors common code * * Copyright (C) 2001 Russell King * (C) 2003 Venkatesh Pallipadi . * (C) 2003 Jun Nakajima * (C) 2009 Alexander Clouter * (c) 2012 Viresh Kumar * * 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. */ #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt #include #include #include #include #include "cpufreq_governor.h" static DEFINE_PER_CPU(struct cpu_dbs_info, cpu_dbs); static DEFINE_MUTEX(gov_dbs_data_mutex); /* Common sysfs tunables */ /** * store_sampling_rate - update sampling rate effective immediately if needed. * * If new rate is smaller than the old, simply updating * dbs.sampling_rate might not be appropriate. For example, if the * original sampling_rate was 1 second and the requested new sampling rate is 10 * ms because the user needs immediate reaction from ondemand governor, but not * sure if higher frequency will be required or not, then, the governor may * change the sampling rate too late; up to 1 second later. Thus, if we are * reducing the sampling rate, we need to make the new value effective * immediately. * * This must be called with dbs_data->mutex held, otherwise traversing * policy_dbs_list isn't safe. */ ssize_t store_sampling_rate(struct dbs_data *dbs_data, const char *buf, size_t count) { struct policy_dbs_info *policy_dbs; unsigned int rate; int ret; ret = sscanf(buf, "%u", &rate); if (ret != 1) return -EINVAL; dbs_data->sampling_rate = max(rate, dbs_data->min_sampling_rate); /* * We are operating under dbs_data->mutex and so the list and its * entries can't be freed concurrently. */ list_for_each_entry(policy_dbs, &dbs_data->policy_dbs_list, list) { mutex_lock(&policy_dbs->timer_mutex); /* * On 32-bit architectures this may race with the * sample_delay_ns read in dbs_update_util_handler(), but that * really doesn't matter. If the read returns a value that's * too big, the sample will be skipped, but the next invocation * of dbs_update_util_handler() (when the update has been * completed) will take a sample. * * If this runs in parallel with dbs_work_handler(), we may end * up overwriting the sample_delay_ns value that it has just * written, but it will be corrected next time a sample is * taken, so it shouldn't be significant. */ gov_update_sample_delay(policy_dbs, 0); mutex_unlock(&policy_dbs->timer_mutex); } return count; } EXPORT_SYMBOL_GPL(store_sampling_rate); /** * gov_update_cpu_data - Update CPU load data. * @dbs_data: Top-level governor data pointer. * * Update CPU load data for all CPUs in the domain governed by @dbs_data * (that may be a single policy or a bunch of them if governor tunables are * system-wide). * * Call under the @dbs_data mutex. */ void gov_update_cpu_data(struct dbs_data *dbs_data) { struct policy_dbs_info *policy_dbs; list_for_each_entry(policy_dbs, &dbs_data->policy_dbs_list, list) { unsigned int j; for_each_cpu(j, policy_dbs->policy->cpus) { struct cpu_dbs_info *j_cdbs = &per_cpu(cpu_dbs, j); j_cdbs->prev_cpu_idle = get_cpu_idle_time(j, &j_cdbs->prev_cpu_wall, dbs_data->io_is_busy); if (dbs_data->ignore_nice_load) j_cdbs->prev_cpu_nice = kcpustat_cpu(j).cpustat[CPUTIME_NICE]; } } } EXPORT_SYMBOL_GPL(gov_update_cpu_data); static inline struct dbs_data *to_dbs_data(struct kobject *kobj) { return container_of(kobj, struct dbs_data, kobj); } static inline struct governor_attr *to_gov_attr(struct attribute *attr) { return container_of(attr, struct governor_attr, attr); } static ssize_t governor_show(struct kobject *kobj, struct attribute *attr, char *buf) { struct dbs_data *dbs_data = to_dbs_data(kobj); struct governor_attr *gattr = to_gov_attr(attr); return gattr->show(dbs_data, buf); } static ssize_t governor_store(struct kobject *kobj, struct attribute *attr, const char *buf, size_t count) { struct dbs_data *dbs_data = to_dbs_data(kobj); struct governor_attr *gattr = to_gov_attr(attr); int ret = -EBUSY; mutex_lock(&dbs_data->mutex); if (dbs_data->usage_count) ret = gattr->store(dbs_data, buf, count); mutex_unlock(&dbs_data->mutex); return ret; } /* * Sysfs Ops for accessing governor attributes. * * All show/store invocations for governor specific sysfs attributes, will first * call the below show/store callbacks and the attribute specific callback will * be called from within it. */ static const struct sysfs_ops governor_sysfs_ops = { .show = governor_show, .store = governor_store, }; unsigned int dbs_update(struct cpufreq_policy *policy) { struct policy_dbs_info *policy_dbs = policy->governor_data; struct dbs_data *dbs_data = policy_dbs->dbs_data; unsigned int ignore_nice = dbs_data->ignore_nice_load; unsigned int max_load = 0; unsigned int sampling_rate, io_busy, j; /* * Sometimes governors may use an additional multiplier to increase * sample delays temporarily. Apply that multiplier to sampling_rate * so as to keep the wake-up-from-idle detection logic a bit * conservative. */ sampling_rate = dbs_data->sampling_rate * policy_dbs->rate_mult; /* * For the purpose of ondemand, waiting for disk IO is an indication * that you're performance critical, and not that the system is actually * idle, so do not add the iowait time to the CPU idle time then. */ io_busy = dbs_data->io_is_busy; /* Get Absolute Load */ for_each_cpu(j, policy->cpus) { struct cpu_dbs_info *j_cdbs = &per_cpu(cpu_dbs, j); u64 cur_wall_time, cur_idle_time; unsigned int idle_time, wall_time; unsigned int load; cur_idle_time = get_cpu_idle_time(j, &cur_wall_time, io_busy); wall_time = cur_wall_time - j_cdbs->prev_cpu_wall; j_cdbs->prev_cpu_wall = cur_wall_time; if (cur_idle_time <= j_cdbs->prev_cpu_idle) { idle_time = 0; } else { idle_time = cur_idle_time - j_cdbs->prev_cpu_idle; j_cdbs->prev_cpu_idle = cur_idle_time; } if (ignore_nice) { u64 cur_nice = kcpustat_cpu(j).cpustat[CPUTIME_NICE]; idle_time += cputime_to_usecs(cur_nice - j_cdbs->prev_cpu_nice); j_cdbs->prev_cpu_nice = cur_nice; } if (unlikely(!wall_time || wall_time < idle_time)) continue; /* * If the CPU had gone completely idle, and a task just woke up * on this CPU now, it would be unfair to calculate 'load' the * usual way for this elapsed time-window, because it will show * near-zero load, irrespective of how CPU intensive that task * actually is. This is undesirable for latency-sensitive bursty * workloads. * * To avoid this, we reuse the 'load' from the previous * time-window and give this task a chance to start with a * reasonably high CPU frequency. (However, we shouldn't over-do * this copy, lest we get stuck at a high load (high frequency) * for too long, even when the current system load has actually * dropped down. So we perform the copy only once, upon the * first wake-up from idle.) * * Detecting this situation is easy: the governor's utilization * update handler would not have run during CPU-idle periods. * Hence, an unusually large 'wall_time' (as compared to the * sampling rate) indicates this scenario. * * prev_load can be zero in two cases and we must recalculate it * for both cases: * - during long idle intervals * - explicitly set to zero */ if (unlikely(wall_time > (2 * sampling_rate) && j_cdbs->prev_load)) { load = j_cdbs->prev_load; /* * Perform a destructive copy, to ensure that we copy * the previous load only once, upon the first wake-up * from idle. */ j_cdbs->prev_load = 0; } else { load = 100 * (wall_time - idle_time) / wall_time; j_cdbs->prev_load = load; } if (load > max_load) max_load = load; } return max_load; } EXPORT_SYMBOL_GPL(dbs_update); static void gov_set_update_util(struct policy_dbs_info *policy_dbs, unsigned int delay_us) { struct cpufreq_policy *policy = policy_dbs->policy; int cpu; gov_update_sample_delay(policy_dbs, delay_us); policy_dbs->last_sample_time = 0; for_each_cpu(cpu, policy->cpus) { struct cpu_dbs_info *cdbs = &per_cpu(cpu_dbs, cpu); cpufreq_set_update_util_data(cpu, &cdbs->update_util); } } static inline void gov_clear_update_util(struct cpufreq_policy *policy) { int i; for_each_cpu(i, policy->cpus) cpufreq_set_update_util_data(i, NULL); synchronize_sched(); } static void gov_cancel_work(struct cpufreq_policy *policy) { struct policy_dbs_info *policy_dbs = policy->governor_data; gov_clear_update_util(policy_dbs->policy); irq_work_sync(&policy_dbs->irq_work); cancel_work_sync(&policy_dbs->work); atomic_set(&policy_dbs->work_count, 0); policy_dbs->work_in_progress = false; } static void dbs_work_handler(struct work_struct *work) { struct policy_dbs_info *policy_dbs; struct cpufreq_policy *policy; struct dbs_governor *gov; policy_dbs = container_of(work, struct policy_dbs_info, work); policy = policy_dbs->policy; gov = dbs_governor_of(policy); /* * Make sure cpufreq_governor_limits() isn't evaluating load or the * ondemand governor isn't updating the sampling rate in parallel. */ mutex_lock(&policy_dbs->timer_mutex); gov_update_sample_delay(policy_dbs, gov->gov_dbs_timer(policy)); mutex_unlock(&policy_dbs->timer_mutex); /* Allow the utilization update handler to queue up more work. */ atomic_set(&policy_dbs->work_count, 0); /* * If the update below is reordered with respect to the sample delay * modification, the utilization update handler may end up using a stale * sample delay value. */ smp_wmb(); policy_dbs->work_in_progress = false; } static void dbs_irq_work(struct irq_work *irq_work) { struct policy_dbs_info *policy_dbs; policy_dbs = container_of(irq_work, struct policy_dbs_info, irq_work); schedule_work_on(smp_processor_id(), &policy_dbs->work); } static void dbs_update_util_handler(struct update_util_data *data, u64 time, unsigned long util, unsigned long max) { struct cpu_dbs_info *cdbs = container_of(data, struct cpu_dbs_info, update_util); struct policy_dbs_info *policy_dbs = cdbs->policy_dbs; u64 delta_ns, lst; /* * The work may not be allowed to be queued up right now. * Possible reasons: * - Work has already been queued up or is in progress. * - It is too early (too little time from the previous sample). */ if (policy_dbs->work_in_progress) return; /* * If the reads below are reordered before the check above, the value * of sample_delay_ns used in the computation may be stale. */ smp_rmb(); lst = READ_ONCE(policy_dbs->last_sample_time); delta_ns = time - lst; if ((s64)delta_ns < policy_dbs->sample_delay_ns) return; /* * If the policy is not shared, the irq_work may be queued up right away * at this point. Otherwise, we need to ensure that only one of the * CPUs sharing the policy will do that. */ if (policy_dbs->is_shared) { if (!atomic_add_unless(&policy_dbs->work_count, 1, 1)) return; /* * If another CPU updated last_sample_time in the meantime, we * shouldn't be here, so clear the work counter and bail out. */ if (unlikely(lst != READ_ONCE(policy_dbs->last_sample_time))) { atomic_set(&policy_dbs->work_count, 0); return; } } policy_dbs->last_sample_time = time; policy_dbs->work_in_progress = true; irq_work_queue(&policy_dbs->irq_work); } static struct policy_dbs_info *alloc_policy_dbs_info(struct cpufreq_policy *policy, struct dbs_governor *gov) { struct policy_dbs_info *policy_dbs; int j; /* Allocate memory for per-policy governor data. */ policy_dbs = gov->alloc(); if (!policy_dbs) return NULL; policy_dbs->policy = policy; mutex_init(&policy_dbs->timer_mutex); atomic_set(&policy_dbs->work_count, 0); init_irq_work(&policy_dbs->irq_work, dbs_irq_work); INIT_WORK(&policy_dbs->work, dbs_work_handler); /* Set policy_dbs for all CPUs, online+offline */ for_each_cpu(j, policy->related_cpus) { struct cpu_dbs_info *j_cdbs = &per_cpu(cpu_dbs, j); j_cdbs->policy_dbs = policy_dbs; j_cdbs->update_util.func = dbs_update_util_handler; } return policy_dbs; } static void free_policy_dbs_info(struct policy_dbs_info *policy_dbs, struct dbs_governor *gov) { int j; mutex_destroy(&policy_dbs->timer_mutex); for_each_cpu(j, policy_dbs->policy->related_cpus) { struct cpu_dbs_info *j_cdbs = &per_cpu(cpu_dbs, j); j_cdbs->policy_dbs = NULL; j_cdbs->update_util.func = NULL; } gov->free(policy_dbs); } static int cpufreq_governor_init(struct cpufreq_policy *policy) { struct dbs_governor *gov = dbs_governor_of(policy); struct dbs_data *dbs_data; struct policy_dbs_info *policy_dbs; unsigned int latency; int ret = 0; /* State should be equivalent to EXIT */ if (policy->governor_data) return -EBUSY; policy_dbs = alloc_policy_dbs_info(policy, gov); if (!policy_dbs) return -ENOMEM; /* Protect gov->gdbs_data against concurrent updates. */ mutex_lock(&gov_dbs_data_mutex); dbs_data = gov->gdbs_data; if (dbs_data) { if (WARN_ON(have_governor_per_policy())) { ret = -EINVAL; goto free_policy_dbs_info; } policy_dbs->dbs_data = dbs_data; policy->governor_data = policy_dbs; mutex_lock(&dbs_data->mutex); dbs_data->usage_count++; list_add(&policy_dbs->list, &dbs_data->policy_dbs_list); mutex_unlock(&dbs_data->mutex); goto out; } dbs_data = kzalloc(sizeof(*dbs_data), GFP_KERNEL); if (!dbs_data) { ret = -ENOMEM; goto free_policy_dbs_info; } INIT_LIST_HEAD(&dbs_data->policy_dbs_list); mutex_init(&dbs_data->mutex); ret = gov->init(dbs_data, !policy->governor->initialized); if (ret) goto free_policy_dbs_info; /* policy latency is in ns. Convert it to us first */ latency = policy->cpuinfo.transition_latency / 1000; if (latency == 0) latency = 1; /* Bring kernel and HW constraints together */ dbs_data->min_sampling_rate = max(dbs_data->min_sampling_rate, MIN_LATENCY_MULTIPLIER * latency); dbs_data->sampling_rate = max(dbs_data->min_sampling_rate, LATENCY_MULTIPLIER * latency); if (!have_governor_per_policy()) gov->gdbs_data = dbs_data; policy->governor_data = policy_dbs; policy_dbs->dbs_data = dbs_data; dbs_data->usage_count = 1; list_add(&policy_dbs->list, &dbs_data->policy_dbs_list); gov->kobj_type.sysfs_ops = &governor_sysfs_ops; ret = kobject_init_and_add(&dbs_data->kobj, &gov->kobj_type, get_governor_parent_kobj(policy), "%s", gov->gov.name); if (!ret) goto out; /* Failure, so roll back. */ pr_err("cpufreq: Governor initialization failed (dbs_data kobject init error %d)\n", ret); policy->governor_data = NULL; if (!have_governor_per_policy()) gov->gdbs_data = NULL; gov->exit(dbs_data, !policy->governor->initialized); kfree(dbs_data); free_policy_dbs_info: free_policy_dbs_info(policy_dbs, gov); out: mutex_unlock(&gov_dbs_data_mutex); return ret; } static int cpufreq_governor_exit(struct cpufreq_policy *policy) { struct dbs_governor *gov = dbs_governor_of(policy); struct policy_dbs_info *policy_dbs = policy->governor_data; struct dbs_data *dbs_data = policy_dbs->dbs_data; int count; /* Protect gov->gdbs_data against concurrent updates. */ mutex_lock(&gov_dbs_data_mutex); mutex_lock(&dbs_data->mutex); list_del(&policy_dbs->list); count = --dbs_data->usage_count; mutex_unlock(&dbs_data->mutex); if (!count) { kobject_put(&dbs_data->kobj); policy->governor_data = NULL; if (!have_governor_per_policy()) gov->gdbs_data = NULL; gov->exit(dbs_data, policy->governor->initialized == 1); mutex_destroy(&dbs_data->mutex); kfree(dbs_data); } else { policy->governor_data = NULL; } free_policy_dbs_info(policy_dbs, gov); mutex_unlock(&gov_dbs_data_mutex); return 0; } static int cpufreq_governor_start(struct cpufreq_policy *policy) { struct dbs_governor *gov = dbs_governor_of(policy); struct policy_dbs_info *policy_dbs = policy->governor_data; struct dbs_data *dbs_data = policy_dbs->dbs_data; unsigned int sampling_rate, ignore_nice, j; unsigned int io_busy; if (!policy->cur) return -EINVAL; policy_dbs->is_shared = policy_is_shared(policy); policy_dbs->rate_mult = 1; sampling_rate = dbs_data->sampling_rate; ignore_nice = dbs_data->ignore_nice_load; io_busy = dbs_data->io_is_busy; for_each_cpu(j, policy->cpus) { struct cpu_dbs_info *j_cdbs = &per_cpu(cpu_dbs, j); unsigned int prev_load; j_cdbs->prev_cpu_idle = get_cpu_idle_time(j, &j_cdbs->prev_cpu_wall, io_busy); prev_load = j_cdbs->prev_cpu_wall - j_cdbs->prev_cpu_idle; j_cdbs->prev_load = 100 * prev_load / (unsigned int)j_cdbs->prev_cpu_wall; if (ignore_nice) j_cdbs->prev_cpu_nice = kcpustat_cpu(j).cpustat[CPUTIME_NICE]; } gov->start(policy); gov_set_update_util(policy_dbs, sampling_rate); return 0; } static int cpufreq_governor_stop(struct cpufreq_policy *policy) { gov_cancel_work(policy); return 0; } static int cpufreq_governor_limits(struct cpufreq_policy *policy) { struct policy_dbs_info *policy_dbs = policy->governor_data; mutex_lock(&policy_dbs->timer_mutex); if (policy->max < policy->cur) __cpufreq_driver_target(policy, policy->max, CPUFREQ_RELATION_H); else if (policy->min > policy->cur) __cpufreq_driver_target(policy, policy->min, CPUFREQ_RELATION_L); gov_update_sample_delay(policy_dbs, 0); mutex_unlock(&policy_dbs->timer_mutex); return 0; } int cpufreq_governor_dbs(struct cpufreq_policy *policy, unsigned int event) { if (event == CPUFREQ_GOV_POLICY_INIT) { return cpufreq_governor_init(policy); } else if (policy->governor_data) { switch (event) { case CPUFREQ_GOV_POLICY_EXIT: return cpufreq_governor_exit(policy); case CPUFREQ_GOV_START: return cpufreq_governor_start(policy); case CPUFREQ_GOV_STOP: return cpufreq_governor_stop(policy); case CPUFREQ_GOV_LIMITS: return cpufreq_governor_limits(policy); } } return -EINVAL; } EXPORT_SYMBOL_GPL(cpufreq_governor_dbs);