From patchwork Mon Feb 22 14:57:10 2016 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Petr Mladek X-Patchwork-Id: 8378491 Return-Path: X-Original-To: patchwork-linux-pm@patchwork.kernel.org Delivered-To: patchwork-parsemail@patchwork2.web.kernel.org Received: from mail.kernel.org (mail.kernel.org [198.145.29.136]) by patchwork2.web.kernel.org (Postfix) with ESMTP id 2EF3DC0553 for ; Mon, 22 Feb 2016 15:00:56 +0000 (UTC) Received: from mail.kernel.org (localhost [127.0.0.1]) by mail.kernel.org (Postfix) with ESMTP id A7F37204AB for ; Mon, 22 Feb 2016 15:00:54 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id E4EA5204EA for ; Mon, 22 Feb 2016 15:00:51 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753145AbcBVPAc (ORCPT ); Mon, 22 Feb 2016 10:00:32 -0500 Received: from mx2.suse.de ([195.135.220.15]:37397 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753117AbcBVPA1 (ORCPT ); Mon, 22 Feb 2016 10:00:27 -0500 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (charybdis-ext.suse.de [195.135.220.254]) by mx2.suse.de (Postfix) with ESMTP id F3138ADBC; Mon, 22 Feb 2016 15:00:25 +0000 (UTC) From: Petr Mladek To: Andrew Morton , Oleg Nesterov , Tejun Heo , Ingo Molnar , Peter Zijlstra Cc: Steven Rostedt , "Paul E. McKenney" , Josh Triplett , Thomas Gleixner , Linus Torvalds , Jiri Kosina , Borislav Petkov , Michal Hocko , linux-mm@kvack.org, Vlastimil Babka , linux-api@vger.kernel.org, linux-kernel@vger.kernel.org, Petr Mladek , Zhang Rui , Eduardo Valentin , Jacob Pan , linux-pm@vger.kernel.org Subject: [PATCH v5 20/20] thermal/intel_powerclamp: Convert the kthread to kthread worker API Date: Mon, 22 Feb 2016 15:57:10 +0100 Message-Id: <1456153030-12400-21-git-send-email-pmladek@suse.com> X-Mailer: git-send-email 1.8.5.6 In-Reply-To: <1456153030-12400-1-git-send-email-pmladek@suse.com> References: <1456153030-12400-1-git-send-email-pmladek@suse.com> Sender: linux-pm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-pm@vger.kernel.org X-Spam-Status: No, score=-6.9 required=5.0 tests=BAYES_00, RCVD_IN_DNSWL_HI, RP_MATCHES_RCVD, UNPARSEABLE_RELAY autolearn=unavailable version=3.3.1 X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on mail.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP Kthreads are currently implemented as an infinite loop. Each has its own variant of checks for terminating, freezing, awakening. In many cases it is unclear to say in which state it is and sometimes it is done a wrong way. The plan is to convert kthreads into kthread_worker or workqueues API. It allows to split the functionality into separate operations. It helps to make a better structure. Also it defines a clean state where no locks are taken, IRQs blocked, the kthread might sleep or even be safely migrated. The kthread worker API is useful when we want to have a dedicated single thread for the work. It helps to make sure that it is available when needed. Also it allows a better control, e.g. define a scheduling priority. This patch converts the intel powerclamp kthreads into the kthread worker because they need to have a good control over the assigned CPUs. IMHO, the most natural way is to split one cycle into two works. First one does some balancing and let the CPU work normal way for some time. The second work checks what the CPU has done in the meantime and put it into C-state to reach the required idle time ratio. The delay between the two works is achieved by the delayed kthread work. The two works have to share some data that used to be local variables of the single kthread function. This is achieved by the new per-CPU struct kthread_worker_data. It might look as a complication. On the other hand, the long original kthread function was not nice either. The patch tries to avoid extra init and cleanup works. All the actions might be done outside the thread. They are moved to the functions that create or destroy the worker. Especially, I checked that the timers are assigned to the right CPU. The two works are queuing each other. It makes it a bit tricky to break it when we want to stop the worker. We use the global and per-worker "clamping" variables to make sure that the re-queuing eventually stops. We also cancel the works to make it faster. Note that the canceling is not reliable because the handling of the two variables and queuing is not synchronized via a lock. But it is not a big deal because it is just an optimization. The job is stopped faster than before in most cases. Signed-off-by: Petr Mladek CC: Zhang Rui CC: Eduardo Valentin CC: Jacob Pan CC: linux-pm@vger.kernel.org Acked-by: Jacob Pan --- drivers/thermal/intel_powerclamp.c | 287 ++++++++++++++++++++++--------------- 1 file changed, 168 insertions(+), 119 deletions(-) diff --git a/drivers/thermal/intel_powerclamp.c b/drivers/thermal/intel_powerclamp.c index cb32c38f9828..964102c2330c 100644 --- a/drivers/thermal/intel_powerclamp.c +++ b/drivers/thermal/intel_powerclamp.c @@ -86,11 +86,27 @@ static unsigned int control_cpu; /* The cpu assigned to collect stat and update */ static bool clamping; +static const struct sched_param sparam = { + .sched_priority = MAX_USER_RT_PRIO / 2, +}; +struct powerclamp_worker_data { + struct kthread_worker *worker; + struct kthread_work balancing_work; + struct delayed_kthread_work idle_injection_work; + struct timer_list wakeup_timer; + unsigned int cpu; + unsigned int count; + unsigned int guard; + unsigned int window_size_now; + unsigned int target_ratio; + unsigned int duration_jiffies; + bool clamping; +}; -static struct task_struct * __percpu *powerclamp_thread; +static struct powerclamp_worker_data * __percpu worker_data; static struct thermal_cooling_device *cooling_dev; static unsigned long *cpu_clamping_mask; /* bit map for tracking per cpu - * clamping thread + * clamping kthread worker */ static unsigned int duration; @@ -368,100 +384,102 @@ static bool powerclamp_adjust_controls(unsigned int target_ratio, return set_target_ratio + guard <= current_ratio; } -static int clamp_thread(void *arg) +static void clamp_balancing_func(struct kthread_work *work) { - int cpunr = (unsigned long)arg; - DEFINE_TIMER(wakeup_timer, noop_timer, 0, 0); - static const struct sched_param param = { - .sched_priority = MAX_USER_RT_PRIO/2, - }; - unsigned int count = 0; - unsigned int target_ratio; + struct powerclamp_worker_data *w_data; + int sleeptime; + unsigned long target_jiffies; + unsigned int compensation; + int interval; /* jiffies to sleep for each attempt */ - set_bit(cpunr, cpu_clamping_mask); - set_freezable(); - init_timer_on_stack(&wakeup_timer); - sched_setscheduler(current, SCHED_FIFO, ¶m); - - while (true == clamping && !kthread_should_stop() && - cpu_online(cpunr)) { - int sleeptime; - unsigned long target_jiffies; - unsigned int guard; - unsigned int compensation = 0; - int interval; /* jiffies to sleep for each attempt */ - unsigned int duration_jiffies = msecs_to_jiffies(duration); - unsigned int window_size_now; - - try_to_freeze(); - /* - * make sure user selected ratio does not take effect until - * the next round. adjust target_ratio if user has changed - * target such that we can converge quickly. - */ - target_ratio = set_target_ratio; - guard = 1 + target_ratio/20; - window_size_now = window_size; - count++; + w_data = container_of(work, struct powerclamp_worker_data, + balancing_work); - /* - * systems may have different ability to enter package level - * c-states, thus we need to compensate the injected idle ratio - * to achieve the actual target reported by the HW. - */ - compensation = get_compensation(target_ratio); - interval = duration_jiffies*100/(target_ratio+compensation); - - /* align idle time */ - target_jiffies = roundup(jiffies, interval); - sleeptime = target_jiffies - jiffies; - if (sleeptime <= 0) - sleeptime = 1; - schedule_timeout_interruptible(sleeptime); - /* - * only elected controlling cpu can collect stats and update - * control parameters. - */ - if (cpunr == control_cpu && !(count%window_size_now)) { - should_skip = - powerclamp_adjust_controls(target_ratio, - guard, window_size_now); - smp_mb(); - } + /* + * make sure user selected ratio does not take effect until + * the next round. adjust target_ratio if user has changed + * target such that we can converge quickly. + */ + w_data->target_ratio = READ_ONCE(set_target_ratio); + w_data->guard = 1 + w_data->target_ratio / 20; + w_data->window_size_now = window_size; + w_data->duration_jiffies = msecs_to_jiffies(duration); + w_data->count++; + + /* + * systems may have different ability to enter package level + * c-states, thus we need to compensate the injected idle ratio + * to achieve the actual target reported by the HW. + */ + compensation = get_compensation(w_data->target_ratio); + interval = w_data->duration_jiffies * 100 / + (w_data->target_ratio + compensation); + + /* align idle time */ + target_jiffies = roundup(jiffies, interval); + sleeptime = target_jiffies - jiffies; + if (sleeptime <= 0) + sleeptime = 1; + + if (clamping && w_data->clamping && cpu_online(w_data->cpu)) + queue_delayed_kthread_work(w_data->worker, + &w_data->idle_injection_work, + sleeptime); +} + +static void clamp_idle_injection_func(struct kthread_work *work) +{ + struct powerclamp_worker_data *w_data; + unsigned long target_jiffies; + + w_data = container_of(work, struct powerclamp_worker_data, + idle_injection_work.work); + + /* + * only elected controlling cpu can collect stats and update + * control parameters. + */ + if (w_data->cpu == control_cpu && + !(w_data->count % w_data->window_size_now)) { + should_skip = + powerclamp_adjust_controls(w_data->target_ratio, + w_data->guard, + w_data->window_size_now); + smp_mb(); + } - if (should_skip) - continue; + if (should_skip) + goto balance; + + target_jiffies = jiffies + w_data->duration_jiffies; + mod_timer(&w_data->wakeup_timer, target_jiffies); + if (unlikely(local_softirq_pending())) + goto balance; + /* + * stop tick sched during idle time, interrupts are still + * allowed. thus jiffies are updated properly. + */ + preempt_disable(); + /* mwait until target jiffies is reached */ + while (time_before(jiffies, target_jiffies)) { + unsigned long ecx = 1; + unsigned long eax = target_mwait; - target_jiffies = jiffies + duration_jiffies; - mod_timer(&wakeup_timer, target_jiffies); - if (unlikely(local_softirq_pending())) - continue; /* - * stop tick sched during idle time, interrupts are still - * allowed. thus jiffies are updated properly. + * REVISIT: may call enter_idle() to notify drivers who + * can save power during cpu idle. same for exit_idle() */ - preempt_disable(); - /* mwait until target jiffies is reached */ - while (time_before(jiffies, target_jiffies)) { - unsigned long ecx = 1; - unsigned long eax = target_mwait; - - /* - * REVISIT: may call enter_idle() to notify drivers who - * can save power during cpu idle. same for exit_idle() - */ - local_touch_nmi(); - stop_critical_timings(); - mwait_idle_with_hints(eax, ecx); - start_critical_timings(); - atomic_inc(&idle_wakeup_counter); - } - preempt_enable(); + local_touch_nmi(); + stop_critical_timings(); + mwait_idle_with_hints(eax, ecx); + start_critical_timings(); + atomic_inc(&idle_wakeup_counter); } - del_timer_sync(&wakeup_timer); - clear_bit(cpunr, cpu_clamping_mask); + preempt_enable(); - return 0; +balance: + if (clamping && w_data->clamping && cpu_online(w_data->cpu)) + queue_kthread_work(w_data->worker, &w_data->balancing_work); } /* @@ -505,22 +523,58 @@ static void poll_pkg_cstate(struct work_struct *dummy) schedule_delayed_work(&poll_pkg_cstate_work, HZ); } -static void start_power_clamp_thread(unsigned long cpu) +static void start_power_clamp_worker(unsigned long cpu) { - struct task_struct **p = per_cpu_ptr(powerclamp_thread, cpu); - struct task_struct *thread; - - thread = kthread_create_on_node(clamp_thread, - (void *) cpu, - cpu_to_node(cpu), - "kidle_inject/%ld", cpu); - if (IS_ERR(thread)) + struct powerclamp_worker_data *w_data = per_cpu_ptr(worker_data, cpu); + struct kthread_worker *worker; + + worker = create_kthread_worker_on_cpu(cpu, KTW_FREEZABLE, + "kidle_inject/%ld"); + if (IS_ERR(worker)) return; - /* bind to cpu here */ - kthread_bind(thread, cpu); - wake_up_process(thread); - *p = thread; + w_data->worker = worker; + w_data->count = 0; + w_data->cpu = cpu; + w_data->clamping = true; + set_bit(cpu, cpu_clamping_mask); + setup_timer(&w_data->wakeup_timer, noop_timer, 0); + sched_setscheduler(worker->task, SCHED_FIFO, &sparam); + init_kthread_work(&w_data->balancing_work, clamp_balancing_func); + init_delayed_kthread_work(&w_data->idle_injection_work, + clamp_idle_injection_func); + queue_kthread_work(w_data->worker, &w_data->balancing_work); +} + +static void stop_power_clamp_worker(unsigned long cpu) +{ + struct powerclamp_worker_data *w_data = per_cpu_ptr(worker_data, cpu); + + if (!w_data->worker) + return; + + w_data->clamping = false; + /* + * Make sure that all works that get queued after this point see + * the clamping disabled. The counter part is not needed because + * there is an implicit memory barrier when the queued work + * is proceed. + */ + smp_wmb(); + cancel_kthread_work_sync(&w_data->balancing_work); + cancel_delayed_kthread_work_sync(&w_data->idle_injection_work); + /* + * The balancing work still might be queued here because + * the handling of the "clapming" variable, cancel, and queue + * operations are not synchronized via a lock. But it is not + * a big deal. The balancing work is fast and destroy kthread + * will wait for it. + */ + del_timer_sync(&w_data->wakeup_timer); + clear_bit(w_data->cpu, cpu_clamping_mask); + destroy_kthread_worker(w_data->worker); + + w_data->worker = NULL; } static int start_power_clamp(void) @@ -545,9 +599,9 @@ static int start_power_clamp(void) clamping = true; schedule_delayed_work(&poll_pkg_cstate_work, 0); - /* start one thread per online cpu */ + /* start one kthread worker per online cpu */ for_each_online_cpu(cpu) { - start_power_clamp_thread(cpu); + start_power_clamp_worker(cpu); } put_online_cpus(); @@ -557,20 +611,17 @@ static int start_power_clamp(void) static void end_power_clamp(void) { int i; - struct task_struct *thread; - clamping = false; /* - * make clamping visible to other cpus and give per cpu clamping threads - * sometime to exit, or gets killed later. + * Block requeuing in all the kthread workers. They will drain and + * stop faster. */ - smp_mb(); - msleep(20); + clamping = false; if (bitmap_weight(cpu_clamping_mask, num_possible_cpus())) { for_each_set_bit(i, cpu_clamping_mask, num_possible_cpus()) { - pr_debug("clamping thread for cpu %d alive, kill\n", i); - thread = *per_cpu_ptr(powerclamp_thread, i); - kthread_stop(thread); + pr_debug("clamping worker for cpu %d alive, destroy\n", + i); + stop_power_clamp_worker(i); } } } @@ -579,15 +630,13 @@ static int powerclamp_cpu_callback(struct notifier_block *nfb, unsigned long action, void *hcpu) { unsigned long cpu = (unsigned long)hcpu; - struct task_struct **percpu_thread = - per_cpu_ptr(powerclamp_thread, cpu); if (false == clamping) goto exit_ok; switch (action) { case CPU_ONLINE: - start_power_clamp_thread(cpu); + start_power_clamp_worker(cpu); /* prefer BSP as controlling CPU */ if (cpu == 0) { control_cpu = 0; @@ -598,7 +647,7 @@ static int powerclamp_cpu_callback(struct notifier_block *nfb, if (test_bit(cpu, cpu_clamping_mask)) { pr_err("cpu %lu dead but powerclamping thread is not\n", cpu); - kthread_stop(*percpu_thread); + stop_power_clamp_worker(cpu); } if (cpu == control_cpu) { control_cpu = smp_processor_id(); @@ -785,8 +834,8 @@ static int __init powerclamp_init(void) window_size = 2; register_hotcpu_notifier(&powerclamp_cpu_notifier); - powerclamp_thread = alloc_percpu(struct task_struct *); - if (!powerclamp_thread) { + worker_data = alloc_percpu(struct powerclamp_worker_data); + if (!worker_data) { retval = -ENOMEM; goto exit_unregister; } @@ -806,7 +855,7 @@ static int __init powerclamp_init(void) return 0; exit_free_thread: - free_percpu(powerclamp_thread); + free_percpu(worker_data); exit_unregister: unregister_hotcpu_notifier(&powerclamp_cpu_notifier); exit_free: @@ -819,7 +868,7 @@ static void __exit powerclamp_exit(void) { unregister_hotcpu_notifier(&powerclamp_cpu_notifier); end_power_clamp(); - free_percpu(powerclamp_thread); + free_percpu(worker_data); thermal_cooling_device_unregister(cooling_dev); kfree(cpu_clamping_mask);