[v10,1/3] cpufreq: Add mechanism for registering utilization update callbacks

Message ID	16016177.YFqb4gVNBo@vostro.rjw.lan (mailing list archive)
State	Accepted, archived
Delegated to:	Rafael Wysocki
Headers	show Return-Path: <linux-pm-owner@kernel.org> From: "Rafael J. Wysocki" <rjw@rjwysocki.net> To: Linux PM list <linux-pm@vger.kernel.org>, Peter Zijlstra <peterz@infradead.org> Cc: Ingo Molnar <mingo@kernel.org>, Linux Kernel Mailing List <linux-kernel@vger.kernel.org>, Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>, Viresh Kumar <viresh.kumar@linaro.org>, Juri Lelli <juri.lelli@arm.com>, Steve Muckle <steve.muckle@linaro.org>, Thomas Gleixner <tglx@linutronix.de> Subject: [PATCH v10 1/3] cpufreq: Add mechanism for registering utilization update callbacks Date: Mon, 15 Feb 2016 22:47:22 +0100 Message-ID: <16016177.YFqb4gVNBo@vostro.rjw.lan> User-Agent: KMail/4.11.5 (Linux/4.5.0-rc1+; KDE/4.11.5; x86_64; ; ) In-Reply-To: <3499355.2JlaSruvOa@vostro.rjw.lan> References: <3071836.JbNxX8hU6x@vostro.rjw.lan> <2044559.7ypXocW9OZ@vostro.rjw.lan> <3499355.2JlaSruvOa@vostro.rjw.lan> MIME-Version: 1.0 Content-Transfer-Encoding: 7Bit Content-Type: text/plain; charset="utf-8" Sender: linux-pm-owner@vger.kernel.org Precedence: bulk

Index: linux-pm/include/linux/cpufreq.h =================================================================== --- linux-pm.orig/include/linux/cpufreq.h +++ linux-pm/include/linux/cpufreq.h @@ -151,6 +151,36 @@ static inline bool policy_is_shared(stru extern struct kobject *cpufreq_global_kobject; #ifdef CONFIG_CPU_FREQ +void cpufreq_update_util(u64 time, unsigned long util, unsigned long max); + +/** + * cpufreq_trigger_update - Trigger CPU performance state evaluation if needed. + * @time: Current time. + * + * The way cpufreq is currently arranged requires it to evaluate the CPU + * performance state (frequency/voltage) on a regular basis to prevent it from + * being stuck in a completely inadequate performance level for too long. + * That is not guaranteed to happen if the updates are only triggered from CFS, + * though, because they may not be coming in if RT or deadline tasks are active + * all the time (or there are RT and DL tasks only). + * + * As a workaround for that issue, this function is called by the RT and DL + * sched classes to trigger extra cpufreq updates to prevent it from stalling, + * but that really is a band-aid. Going forward it should be replaced with + * solutions targeted more specifically at RT and DL tasks. + */ +static inline void cpufreq_trigger_update(u64 time) +{ + cpufreq_update_util(time, ULONG_MAX, 0); +} + +struct update_util_data { + void (*func)(struct update_util_data *data, + u64 time, unsigned long util, unsigned long max); +}; + +void cpufreq_set_update_util_data(int cpu, struct update_util_data *data); + unsigned int cpufreq_get(unsigned int cpu); unsigned int cpufreq_quick_get(unsigned int cpu); unsigned int cpufreq_quick_get_max(unsigned int cpu); @@ -162,6 +192,10 @@ int cpufreq_update_policy(unsigned int c bool have_governor_per_policy(void); struct kobject *get_governor_parent_kobj(struct cpufreq_policy *policy); #else +static inline void cpufreq_update_util(u64 time, unsigned long util, + unsigned long max) {} +static inline void cpufreq_trigger_update(u64 time) {} + static inline unsigned int cpufreq_get(unsigned int cpu) { return 0; Index: linux-pm/kernel/sched/sched.h =================================================================== --- linux-pm.orig/kernel/sched/sched.h +++ linux-pm/kernel/sched/sched.h @@ -9,6 +9,7 @@ #include <linux/irq_work.h> #include <linux/tick.h> #include <linux/slab.h> +#include <linux/cpufreq.h> #include "cpupri.h" #include "cpudeadline.h" Index: linux-pm/kernel/sched/fair.c =================================================================== --- linux-pm.orig/kernel/sched/fair.c +++ linux-pm/kernel/sched/fair.c @@ -2824,7 +2824,8 @@ static inline void update_load_avg(struc { struct cfs_rq *cfs_rq = cfs_rq_of(se); u64 now = cfs_rq_clock_task(cfs_rq); - int cpu = cpu_of(rq_of(cfs_rq)); + struct rq *rq = rq_of(cfs_rq); + int cpu = cpu_of(rq); /* * Track task load average for carrying it to new CPU after migrated, and @@ -2836,6 +2837,29 @@ static inline void update_load_avg(struc if (update_cfs_rq_load_avg(now, cfs_rq) && update_tg) update_tg_load_avg(cfs_rq, 0); + + if (cpu == smp_processor_id() && &rq->cfs == cfs_rq) { + unsigned long max = rq->cpu_capacity_orig; + + /* + * There are a few boundary cases this might miss but it should + * get called often enough that that should (hopefully) not be + * a real problem -- added to that it only calls on the local + * CPU, so if we enqueue remotely we'll miss an update, but + * the next tick/schedule should update. + * + * It will not get called when we go idle, because the idle + * thread is a different class (!fair), nor will the utilization + * number include things like RT tasks. + * + * As is, the util number is not freq-invariant (we'd have to + * implement arch_scale_freq_capacity() for that). + * + * See cpu_util(). + */ + cpufreq_update_util(rq_clock(rq), + min(cfs_rq->avg.util_avg, max), max); + } } static void attach_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se) Index: linux-pm/kernel/sched/deadline.c =================================================================== --- linux-pm.orig/kernel/sched/deadline.c +++ linux-pm/kernel/sched/deadline.c @@ -726,6 +726,10 @@ static void update_curr_dl(struct rq *rq if (!dl_task(curr) || !on_dl_rq(dl_se)) return; + /* Kick cpufreq (see the comment in linux/cpufreq.h). */ + if (cpu_of(rq) == smp_processor_id()) + cpufreq_trigger_update(rq_clock(rq)); + /* * Consumed budget is computed considering the time as * observed by schedulable tasks (excluding time spent Index: linux-pm/kernel/sched/rt.c =================================================================== --- linux-pm.orig/kernel/sched/rt.c +++ linux-pm/kernel/sched/rt.c @@ -945,6 +945,10 @@ static void update_curr_rt(struct rq *rq if (curr->sched_class != &rt_sched_class) return; + /* Kick cpufreq (see the comment in linux/cpufreq.h). */ + if (cpu_of(rq) == smp_processor_id()) + cpufreq_trigger_update(rq_clock(rq)); + delta_exec = rq_clock_task(rq) - curr->se.exec_start; if (unlikely((s64)delta_exec <= 0)) return; Index: linux-pm/drivers/cpufreq/cpufreq.c =================================================================== --- linux-pm.orig/drivers/cpufreq/cpufreq.c +++ linux-pm/drivers/cpufreq/cpufreq.c @@ -102,6 +102,51 @@ static LIST_HEAD(cpufreq_governor_list); static struct cpufreq_driver *cpufreq_driver; static DEFINE_PER_CPU(struct cpufreq_policy *, cpufreq_cpu_data); static DEFINE_RWLOCK(cpufreq_driver_lock); + +static DEFINE_PER_CPU(struct update_util_data *, cpufreq_update_util_data); + +/** + * cpufreq_set_update_util_data - Populate the CPU's update_util_data pointer. + * @cpu: The CPU to set the pointer for. + * @data: New pointer value. + * + * Set and publish the update_util_data pointer for the given CPU. That pointer + * points to a struct update_util_data object containing a callback function + * to call from cpufreq_update_util(). That function will be called from an RCU + * read-side critical section, so it must not sleep. + * + * Callers must use RCU callbacks to free any memory that might be accessed + * via the old update_util_data pointer or invoke synchronize_rcu() right after + * this function to avoid use-after-free. + */ +void cpufreq_set_update_util_data(int cpu, struct update_util_data *data) +{ + rcu_assign_pointer(per_cpu(cpufreq_update_util_data, cpu), data); +} +EXPORT_SYMBOL_GPL(cpufreq_set_update_util_data); + +/** + * cpufreq_update_util - Take a note about CPU utilization changes. + * @time: Current time. + * @util: Current utilization. + * @max: Utilization ceiling. + * + * This function is called by the scheduler on every invocation of + * update_load_avg() on the CPU whose utilization is being updated. + */ +void cpufreq_update_util(u64 time, unsigned long util, unsigned long max) +{ + struct update_util_data *data; + + rcu_read_lock(); + + data = rcu_dereference(*this_cpu_ptr(&cpufreq_update_util_data)); + if (data && data->func) + data->func(data, time, util, max); + + rcu_read_unlock(); +} + DEFINE_MUTEX(cpufreq_governor_lock); /* Flag to suspend/resume CPUFreq governors */

[v10,1/3] cpufreq: Add mechanism for registering utilization update callbacks

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