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         struct timespec boot_time;
  41         unsigned int target;
  42         unsigned int usage;
  43         int delay;
  44         u64 curr_used;
  45         u64 curr_boot;
  46         s32 diff_used;
  47         s32 diff_boot;
  48         int cpus;
  49         int i;
  50
  51         if (test_and_clear_bit(LED_BLINK_BRIGHTNESS_CHANGE, &led_cdev->work_flags))
  52                 led_cdev->blink_brightness = led_cdev->new_blink_brightness;
  53
  54         if (unlikely(panic_detected)) {
  55                 /* full brightness in case of panic */
  56                 led_set_brightness_nosleep(led_cdev, led_cdev->blink_brightness);
  57                 return;
  58         }
  59
  60         get_monotonic_boottime(&boot_time);
  61
  62         cpus = 0;
  63         curr_used = 0;
  64
  65         for_each_possible_cpu(i) {
  66                 curr_used += kcpustat_cpu(i).cpustat[CPUTIME_USER]
  67                           +  kcpustat_cpu(i).cpustat[CPUTIME_NICE]
  68                           +  kcpustat_cpu(i).cpustat[CPUTIME_SYSTEM]
  69                           +  kcpustat_cpu(i).cpustat[CPUTIME_SOFTIRQ]
  70                           +  kcpustat_cpu(i).cpustat[CPUTIME_IRQ];
  71                 cpus++;
  72         }
  73
  74         /* We come here every 100ms in the worst case, so that's 100M ns of
  75          * cumulated time. By dividing by 2^16, we get the time resolution
  76          * down to 16us, ensuring we won't overflow 32-bit computations below
  77          * even up to 3k CPUs, while keeping divides cheap on smaller systems.
  78          */
  79         curr_boot = timespec_to_ns(&boot_time) * cpus;
  80         diff_boot = (curr_boot - activity_data->last_boot) >> 16;
  81         diff_used = (curr_used - activity_data->last_used) >> 16;
  82         activity_data->last_boot = curr_boot;
  83         activity_data->last_used = curr_used;
  84
  85         if (diff_boot <= 0 || diff_used < 0)
  86                 usage = 0;
  87         else if (diff_used >= diff_boot)
  88                 usage = 100;
  89         else
  90                 usage = 100 * diff_used / diff_boot;
  91
  92         /*
  93          * Now we know the total boot_time multiplied by the number of CPUs, and
  94          * the total idle+wait time for all CPUs. We'll compare how they evolved
  95          * since last call. The % of overall CPU usage is :
  96          *
  97          *      1 - delta_idle / delta_boot
  98          *
  99          * What we want is that when the CPU usage is zero, the LED must blink
 100          * slowly with very faint flashes that are detectable but not disturbing
 101          * (typically 10ms every second, or 10ms ON, 990ms OFF). Then we want
 102          * blinking frequency to increase up to the point where the load is
 103          * enough to saturate one core in multi-core systems or 50% in single
 104          * core systems. At this point it should reach 10 Hz with a 10/90 duty
 105          * cycle (10ms ON, 90ms OFF). After this point, the blinking frequency
 106          * remains stable (10 Hz) and only the duty cycle increases to report
 107          * the activity, up to the point where we have 90ms ON, 10ms OFF when
 108          * all cores are saturated. It's important that the LED never stays in
 109          * a steady state so that it's easy to distinguish an idle or saturated
 110          * machine from a hung one.
 111          *
 112          * This gives us :
 113          *   - a target CPU usage of min(50%, 100%/#CPU) for a 10% duty cycle
 114          *     (10ms ON, 90ms OFF)
 115          *   - below target :
 116          *      ON_ms  = 10
 117          *      OFF_ms = 90 + (1 - usage/target) * 900
 118          *   - above target :
 119          *      ON_ms  = 10 + (usage-target)/(100%-target) * 80
 120          *      OFF_ms = 90 - (usage-target)/(100%-target) * 80
 121          *
 122          * In order to keep a good responsiveness, we cap the sleep time to
 123          * 100 ms and keep track of the sleep time left. This allows us to
 124          * quickly change it if needed.
 125          */
 126
 127         activity_data->time_left -= 100;
 128         if (activity_data->time_left <= 0) {
 129                 activity_data->time_left = 0;
 130                 activity_data->state = !activity_data->state;
 131                 led_set_brightness_nosleep(led_cdev,
 132                         (activity_data->state ^ activity_data->invert) ?
 133                         led_cdev->blink_brightness : LED_OFF);
 134         }
 135
 136         target = (cpus > 1) ? (100 / cpus) : 50;
 137
 138         if (usage < target)
 139                 delay = activity_data->state ?
 140                         10 :                        /* ON  */
 141                         990 - 900 * usage / target; /* OFF */
 142         else
 143                 delay = activity_data->state ?
 144                         10 + 80 * (usage - target) / (100 - target) : /* ON  */
 145                         90 - 80 * (usage - target) / (100 - target);  /* OFF */
 146
 147
 148         if (!activity_data->time_left || delay <= activity_data->time_left)
 149                 activity_data->time_left = delay;
 150
 151         delay = min_t(int, activity_data->time_left, 100);
 152         mod_timer(&activity_data->timer, jiffies + msecs_to_jiffies(delay));
 153 }
 154
 155 static ssize_t led_invert_show(struct device *dev,
 156                                struct device_attribute *attr, char *buf)
 157 {
 158         struct led_classdev *led_cdev = dev_get_drvdata(dev);
 159         struct activity_data *activity_data = led_cdev->trigger_data;
 160
 161         return sprintf(buf, "%u\n", activity_data->invert);
 162 }
 163
 164 static ssize_t led_invert_store(struct device *dev,
 165                                 struct device_attribute *attr,
 166                                 const char *buf, size_t size)
 167 {
 168         struct led_classdev *led_cdev = dev_get_drvdata(dev);
 169         struct activity_data *activity_data = led_cdev->trigger_data;
 170         unsigned long state;
 171         int ret;
 172
 173         ret = kstrtoul(buf, 0, &state);
 174         if (ret)
 175                 return ret;
 176
 177         activity_data->invert = !!state;
 178
 179         return size;
 180 }
 181
 182 static DEVICE_ATTR(invert, 0644, led_invert_show, led_invert_store);
 183
 184 static void activity_activate(struct led_classdev *led_cdev)
 185 {
 186         struct activity_data *activity_data;
 187         int rc;
 188
 189         activity_data = kzalloc(sizeof(*activity_data), GFP_KERNEL);
 190         if (!activity_data)
 191                 return;
 192
 193         led_cdev->trigger_data = activity_data;
 194         rc = device_create_file(led_cdev->dev, &dev_attr_invert);
 195         if (rc) {
 196                 kfree(led_cdev->trigger_data);
 197                 return;
 198         }
 199
 200         activity_data->led_cdev = led_cdev;
 201         timer_setup(&activity_data->timer, led_activity_function, 0);
 202         if (!led_cdev->blink_brightness)
 203                 led_cdev->blink_brightness = led_cdev->max_brightness;
 204         led_activity_function(&activity_data->timer);
 205         set_bit(LED_BLINK_SW, &led_cdev->work_flags);
 206         led_cdev->activated = true;
 207 }
 208
 209 static void activity_deactivate(struct led_classdev *led_cdev)
 210 {
 211         struct activity_data *activity_data = led_cdev->trigger_data;
 212
 213         if (led_cdev->activated) {
 214                 del_timer_sync(&activity_data->timer);
 215                 device_remove_file(led_cdev->dev, &dev_attr_invert);
 216                 kfree(activity_data);
 217                 clear_bit(LED_BLINK_SW, &led_cdev->work_flags);
 218                 led_cdev->activated = false;
 219         }
 220 }
 221
 222 static struct led_trigger activity_led_trigger = {
 223         .name       = "activity",
 224         .activate   = activity_activate,
 225         .deactivate = activity_deactivate,
 226 };
 227
 228 static int activity_reboot_notifier(struct notifier_block *nb,
 229                                     unsigned long code, void *unused)
 230 {
 231         led_trigger_unregister(&activity_led_trigger);
 232         return NOTIFY_DONE;
 233 }
 234
 235 static int activity_panic_notifier(struct notifier_block *nb,
 236                                    unsigned long code, void *unused)
 237 {
 238         panic_detected = 1;
 239         return NOTIFY_DONE;
 240 }
 241
 242 static struct notifier_block activity_reboot_nb = {
 243         .notifier_call = activity_reboot_notifier,
 244 };
 245
 246 static struct notifier_block activity_panic_nb = {
 247         .notifier_call = activity_panic_notifier,
 248 };
 249
 250 static int __init activity_init(void)
 251 {
 252         int rc = led_trigger_register(&activity_led_trigger);
 253
 254         if (!rc) {
 255                 atomic_notifier_chain_register(&panic_notifier_list,
 256                                                &activity_panic_nb);
 257                 register_reboot_notifier(&activity_reboot_nb);
 258         }
 259         return rc;
 260 }
 261
 262 static void __exit activity_exit(void)
 263 {
 264         unregister_reboot_notifier(&activity_reboot_nb);
 265         atomic_notifier_chain_unregister(&panic_notifier_list,
 266                                          &activity_panic_nb);
 267         led_trigger_unregister(&activity_led_trigger);
 268 }
 269
 270 module_init(activity_init);
 271 module_exit(activity_exit);
 272
 273 MODULE_AUTHOR("Willy Tarreau <w@1wt.eu>");
 274 MODULE_DESCRIPTION("Activity LED trigger");
 275 MODULE_LICENSE("GPL");