drivers/leds/trigger/ledtrig-activity.c

   1 /*
   2  * Activity LED trigger
   3  *
   4  * Copyright (C) 2017 Willy Tarreau <w@1wt.eu>
   5  * Partially based on Atsushi Nemoto's ledtrig-heartbeat.c.
   6  *
   7  * This program is free software; you can redistribute it and/or modify
   8  * it under the terms of the GNU General Public License version 2 as
   9  * published by the Free Software Foundation.
  10  */
  11
  12 #include <linux/init.h>
  13 #include <linux/kernel.h>
  14 #include <linux/kernel_stat.h>
  15 #include <linux/leds.h>
  16 #include <linux/module.h>
  17 #include <linux/reboot.h>
  18 #include <linux/sched.h>
  19 #include <linux/slab.h>
  20 #include <linux/timer.h>
  21 #include "../leds.h"
  22
  23 static int panic_detected;
  24
  25 struct activity_data {
  26         struct timer_list timer;
  27         struct led_classdev *led_cdev;
  28         u64 last_used;
  29         u64 last_boot;
  30         int time_left;
  31         int state;
  32         int invert;
  33 };
  34
  35 static void led_activity_function(struct timer_list *t)
  36 {
  37         struct activity_data *activity_data = from_timer(activity_data, t,
  38                                                          timer);
  39         struct led_classdev *led_cdev = activity_data->led_cdev;
  40         unsigned int target;
  41         unsigned int usage;
  42         int delay;
  43         u64 curr_used;
  44         u64 curr_boot;
  45         s32 diff_used;
  46         s32 diff_boot;
  47         int cpus;
  48         int i;
  49
  50         if (test_and_clear_bit(LED_BLINK_BRIGHTNESS_CHANGE, &led_cdev->work_flags))
  51                 led_cdev->blink_brightness = led_cdev->new_blink_brightness;
  52
  53         if (unlikely(panic_detected)) {
  54                 /* full brightness in case of panic */
  55                 led_set_brightness_nosleep(led_cdev, led_cdev->blink_brightness);
  56                 return;
  57         }
  58
  59         cpus = 0;
  60         curr_used = 0;
  61
  62         for_each_possible_cpu(i) {
  63                 curr_used += kcpustat_cpu(i).cpustat[CPUTIME_USER]
  64                           +  kcpustat_cpu(i).cpustat[CPUTIME_NICE]
  65                           +  kcpustat_cpu(i).cpustat[CPUTIME_SYSTEM]
  66                           +  kcpustat_cpu(i).cpustat[CPUTIME_SOFTIRQ]
  67                           +  kcpustat_cpu(i).cpustat[CPUTIME_IRQ];
  68                 cpus++;
  69         }
  70
  71         /* We come here every 100ms in the worst case, so that's 100M ns of
  72          * cumulated time. By dividing by 2^16, we get the time resolution
  73          * down to 16us, ensuring we won't overflow 32-bit computations below
  74          * even up to 3k CPUs, while keeping divides cheap on smaller systems.
  75          */
  76         curr_boot = ktime_get_boot_ns() * cpus;
  77         diff_boot = (curr_boot - activity_data->last_boot) >> 16;
  78         diff_used = (curr_used - activity_data->last_used) >> 16;
  79         activity_data->last_boot = curr_boot;
  80         activity_data->last_used = curr_used;
  81
  82         if (diff_boot <= 0 || diff_used < 0)
  83                 usage = 0;
  84         else if (diff_used >= diff_boot)
  85                 usage = 100;
  86         else
  87                 usage = 100 * diff_used / diff_boot;
  88
  89         /*
  90          * Now we know the total boot_time multiplied by the number of CPUs, and
  91          * the total idle+wait time for all CPUs. We'll compare how they evolved
  92          * since last call. The % of overall CPU usage is :
  93          *
  94          *      1 - delta_idle / delta_boot
  95          *
  96          * What we want is that when the CPU usage is zero, the LED must blink
  97          * slowly with very faint flashes that are detectable but not disturbing
  98          * (typically 10ms every second, or 10ms ON, 990ms OFF). Then we want
  99          * blinking frequency to increase up to the point where the load is
 100          * enough to saturate one core in multi-core systems or 50% in single
 101          * core systems. At this point it should reach 10 Hz with a 10/90 duty
 102          * cycle (10ms ON, 90ms OFF). After this point, the blinking frequency
 103          * remains stable (10 Hz) and only the duty cycle increases to report
 104          * the activity, up to the point where we have 90ms ON, 10ms OFF when
 105          * all cores are saturated. It's important that the LED never stays in
 106          * a steady state so that it's easy to distinguish an idle or saturated
 107          * machine from a hung one.
 108          *
 109          * This gives us :
 110          *   - a target CPU usage of min(50%, 100%/#CPU) for a 10% duty cycle
 111          *     (10ms ON, 90ms OFF)
 112          *   - below target :
 113          *      ON_ms  = 10
 114          *      OFF_ms = 90 + (1 - usage/target) * 900
 115          *   - above target :
 116          *      ON_ms  = 10 + (usage-target)/(100%-target) * 80
 117          *      OFF_ms = 90 - (usage-target)/(100%-target) * 80
 118          *
 119          * In order to keep a good responsiveness, we cap the sleep time to
 120          * 100 ms and keep track of the sleep time left. This allows us to
 121          * quickly change it if needed.
 122          */
 123
 124         activity_data->time_left -= 100;
 125         if (activity_data->time_left <= 0) {
 126                 activity_data->time_left = 0;
 127                 activity_data->state = !activity_data->state;
 128                 led_set_brightness_nosleep(led_cdev,
 129                         (activity_data->state ^ activity_data->invert) ?
 130                         led_cdev->blink_brightness : LED_OFF);
 131         }
 132
 133         target = (cpus > 1) ? (100 / cpus) : 50;
 134
 135         if (usage < target)
 136                 delay = activity_data->state ?
 137                         10 :                        /* ON  */
 138                         990 - 900 * usage / target; /* OFF */
 139         else
 140                 delay = activity_data->state ?
 141                         10 + 80 * (usage - target) / (100 - target) : /* ON  */
 142                         90 - 80 * (usage - target) / (100 - target);  /* OFF */
 143
 144
 145         if (!activity_data->time_left || delay <= activity_data->time_left)
 146                 activity_data->time_left = delay;
 147
 148         delay = min_t(int, activity_data->time_left, 100);
 149         mod_timer(&activity_data->timer, jiffies + msecs_to_jiffies(delay));
 150 }
 151
 152 static ssize_t led_invert_show(struct device *dev,
 153                                struct device_attribute *attr, char *buf)
 154 {
 155         struct activity_data *activity_data = led_trigger_get_drvdata(dev);
 156
 157         return sprintf(buf, "%u\n", activity_data->invert);
 158 }
 159
 160 static ssize_t led_invert_store(struct device *dev,
 161                                 struct device_attribute *attr,
 162                                 const char *buf, size_t size)
 163 {
 164         struct activity_data *activity_data = led_trigger_get_drvdata(dev);
 165         unsigned long state;
 166         int ret;
 167
 168         ret = kstrtoul(buf, 0, &state);
 169         if (ret)
 170                 return ret;
 171
 172         activity_data->invert = !!state;
 173
 174         return size;
 175 }
 176
 177 static DEVICE_ATTR(invert, 0644, led_invert_show, led_invert_store);
 178
 179 static struct attribute *activity_led_attrs[] = {
 180         &dev_attr_invert.attr,
 181         NULL
 182 };
 183 ATTRIBUTE_GROUPS(activity_led);
 184
 185 static int activity_activate(struct led_classdev *led_cdev)
 186 {
 187         struct activity_data *activity_data;
 188
 189         activity_data = kzalloc(sizeof(*activity_data), GFP_KERNEL);
 190         if (!activity_data)
 191                 return -ENOMEM;
 192
 193         led_set_trigger_data(led_cdev, activity_data);
 194
 195         activity_data->led_cdev = led_cdev;
 196         timer_setup(&activity_data->timer, led_activity_function, 0);
 197         if (!led_cdev->blink_brightness)
 198                 led_cdev->blink_brightness = led_cdev->max_brightness;
 199         led_activity_function(&activity_data->timer);
 200         set_bit(LED_BLINK_SW, &led_cdev->work_flags);
 201
 202         return 0;
 203 }
 204
 205 static void activity_deactivate(struct led_classdev *led_cdev)
 206 {
 207         struct activity_data *activity_data = led_get_trigger_data(led_cdev);
 208
 209         del_timer_sync(&activity_data->timer);
 210         kfree(activity_data);
 211         clear_bit(LED_BLINK_SW, &led_cdev->work_flags);
 212 }
 213
 214 static struct led_trigger activity_led_trigger = {
 215         .name       = "activity",
 216         .activate   = activity_activate,
 217         .deactivate = activity_deactivate,
 218         .groups     = activity_led_groups,
 219 };
 220
 221 static int activity_reboot_notifier(struct notifier_block *nb,
 222                                     unsigned long code, void *unused)
 223 {
 224         led_trigger_unregister(&activity_led_trigger);
 225         return NOTIFY_DONE;
 226 }
 227
 228 static int activity_panic_notifier(struct notifier_block *nb,
 229                                    unsigned long code, void *unused)
 230 {
 231         panic_detected = 1;
 232         return NOTIFY_DONE;
 233 }
 234
 235 static struct notifier_block activity_reboot_nb = {
 236         .notifier_call = activity_reboot_notifier,
 237 };
 238
 239 static struct notifier_block activity_panic_nb = {
 240         .notifier_call = activity_panic_notifier,
 241 };
 242
 243 static int __init activity_init(void)
 244 {
 245         int rc = led_trigger_register(&activity_led_trigger);
 246
 247         if (!rc) {
 248                 atomic_notifier_chain_register(&panic_notifier_list,
 249                                                &activity_panic_nb);
 250                 register_reboot_notifier(&activity_reboot_nb);
 251         }
 252         return rc;
 253 }
 254
 255 static void __exit activity_exit(void)
 256 {
 257         unregister_reboot_notifier(&activity_reboot_nb);
 258         atomic_notifier_chain_unregister(&panic_notifier_list,
 259                                          &activity_panic_nb);
 260         led_trigger_unregister(&activity_led_trigger);
 261 }
 262
 263 module_init(activity_init);
 264 module_exit(activity_exit);
 265
 266 MODULE_AUTHOR("Willy Tarreau <w@1wt.eu>");
 267 MODULE_DESCRIPTION("Activity LED trigger");
 268 MODULE_LICENSE("GPL v2");