leds/trigger/ledtrig-activity.c

0001 // SPDX-License-Identifier: GPL-2.0-only
0002 /*
0003  * Activity LED trigger
0004  *
0005  * Copyright (C) 2017 Willy Tarreau <w@1wt.eu>
0006  * Partially based on Atsushi Nemoto's ledtrig-heartbeat.c.
0007  */
0008
0009 #include <linux/init.h>
0010 #include <linux/kernel.h>
0011 #include <linux/kernel_stat.h>
0012 #include <linux/leds.h>
0013 #include <linux/module.h>
0014 #include <linux/panic_notifier.h>
0015 #include <linux/reboot.h>
0016 #include <linux/sched.h>
0017 #include <linux/slab.h>
0018 #include <linux/timer.h>
0019 #include "../leds.h"
0020
0021 static int panic_detected;
0022
0023 struct activity_data {
0024     struct timer_list timer;
0025     struct led_classdev *led_cdev;
0026     u64 last_used;
0027     u64 last_boot;
0028     int time_left;
0029     int state;
0030     int invert;
0031 };
0032
0033 static void led_activity_function(struct timer_list *t)
0034 {
0035     struct activity_data *activity_data = from_timer(activity_data, t,
0036                              timer);
0037     struct led_classdev *led_cdev = activity_data->led_cdev;
0038     unsigned int target;
0039     unsigned int usage;
0040     int delay;
0041     u64 curr_used;
0042     u64 curr_boot;
0043     s32 diff_used;
0044     s32 diff_boot;
0045     int cpus;
0046     int i;
0047
0048     if (test_and_clear_bit(LED_BLINK_BRIGHTNESS_CHANGE, &led_cdev->work_flags))
0049         led_cdev->blink_brightness = led_cdev->new_blink_brightness;
0050
0051     if (unlikely(panic_detected)) {
0052         /* full brightness in case of panic */
0053         led_set_brightness_nosleep(led_cdev, led_cdev->blink_brightness);
0054         return;
0055     }
0056
0057     cpus = 0;
0058     curr_used = 0;
0059
0060     for_each_possible_cpu(i) {
0061         struct kernel_cpustat kcpustat;
0062
0063         kcpustat_cpu_fetch(&kcpustat, i);
0064
0065         curr_used += kcpustat.cpustat[CPUTIME_USER]
0066               +  kcpustat.cpustat[CPUTIME_NICE]
0067               +  kcpustat.cpustat[CPUTIME_SYSTEM]
0068               +  kcpustat.cpustat[CPUTIME_SOFTIRQ]
0069               +  kcpustat.cpustat[CPUTIME_IRQ];
0070         cpus++;
0071     }
0072
0073     /* We come here every 100ms in the worst case, so that's 100M ns of
0074      * cumulated time. By dividing by 2^16, we get the time resolution
0075      * down to 16us, ensuring we won't overflow 32-bit computations below
0076      * even up to 3k CPUs, while keeping divides cheap on smaller systems.
0077      */
0078     curr_boot = ktime_get_boottime_ns() * cpus;
0079     diff_boot = (curr_boot - activity_data->last_boot) >> 16;
0080     diff_used = (curr_used - activity_data->last_used) >> 16;
0081     activity_data->last_boot = curr_boot;
0082     activity_data->last_used = curr_used;
0083
0084     if (diff_boot <= 0 || diff_used < 0)
0085         usage = 0;
0086     else if (diff_used >= diff_boot)
0087         usage = 100;
0088     else
0089         usage = 100 * diff_used / diff_boot;
0090
0091     /*
0092      * Now we know the total boot_time multiplied by the number of CPUs, and
0093      * the total idle+wait time for all CPUs. We'll compare how they evolved
0094      * since last call. The % of overall CPU usage is :
0095      *
0096      *      1 - delta_idle / delta_boot
0097      *
0098      * What we want is that when the CPU usage is zero, the LED must blink
0099      * slowly with very faint flashes that are detectable but not disturbing
0100      * (typically 10ms every second, or 10ms ON, 990ms OFF). Then we want
0101      * blinking frequency to increase up to the point where the load is
0102      * enough to saturate one core in multi-core systems or 50% in single
0103      * core systems. At this point it should reach 10 Hz with a 10/90 duty
0104      * cycle (10ms ON, 90ms OFF). After this point, the blinking frequency
0105      * remains stable (10 Hz) and only the duty cycle increases to report
0106      * the activity, up to the point where we have 90ms ON, 10ms OFF when
0107      * all cores are saturated. It's important that the LED never stays in
0108      * a steady state so that it's easy to distinguish an idle or saturated
0109      * machine from a hung one.
0110      *
0111      * This gives us :
0112      *   - a target CPU usage of min(50%, 100%/#CPU) for a 10% duty cycle
0113      *     (10ms ON, 90ms OFF)
0114      *   - below target :
0115      *      ON_ms  = 10
0116      *      OFF_ms = 90 + (1 - usage/target) * 900
0117      *   - above target :
0118      *      ON_ms  = 10 + (usage-target)/(100%-target) * 80
0119      *      OFF_ms = 90 - (usage-target)/(100%-target) * 80
0120      *
0121      * In order to keep a good responsiveness, we cap the sleep time to
0122      * 100 ms and keep track of the sleep time left. This allows us to
0123      * quickly change it if needed.
0124      */
0125
0126     activity_data->time_left -= 100;
0127     if (activity_data->time_left <= 0) {
0128         activity_data->time_left = 0;
0129         activity_data->state = !activity_data->state;
0130         led_set_brightness_nosleep(led_cdev,
0131             (activity_data->state ^ activity_data->invert) ?
0132             led_cdev->blink_brightness : LED_OFF);
0133     }
0134
0135     target = (cpus > 1) ? (100 / cpus) : 50;
0136
0137     if (usage < target)
0138         delay = activity_data->state ?
0139             10 :                        /* ON  */
0140             990 - 900 * usage / target; /* OFF */
0141     else
0142         delay = activity_data->state ?
0143             10 + 80 * (usage - target) / (100 - target) : /* ON  */
0144             90 - 80 * (usage - target) / (100 - target);  /* OFF */
0145
0146
0147     if (!activity_data->time_left || delay <= activity_data->time_left)
0148         activity_data->time_left = delay;
0149
0150     delay = min_t(int, activity_data->time_left, 100);
0151     mod_timer(&activity_data->timer, jiffies + msecs_to_jiffies(delay));
0152 }
0153
0154 static ssize_t led_invert_show(struct device *dev,
0155                                struct device_attribute *attr, char *buf)
0156 {
0157     struct activity_data *activity_data = led_trigger_get_drvdata(dev);
0158
0159     return sprintf(buf, "%u\n", activity_data->invert);
0160 }
0161
0162 static ssize_t led_invert_store(struct device *dev,
0163                                 struct device_attribute *attr,
0164                                 const char *buf, size_t size)
0165 {
0166     struct activity_data *activity_data = led_trigger_get_drvdata(dev);
0167     unsigned long state;
0168     int ret;
0169
0170     ret = kstrtoul(buf, 0, &state);
0171     if (ret)
0172         return ret;
0173
0174     activity_data->invert = !!state;
0175
0176     return size;
0177 }
0178
0179 static DEVICE_ATTR(invert, 0644, led_invert_show, led_invert_store);
0180
0181 static struct attribute *activity_led_attrs[] = {
0182     &dev_attr_invert.attr,
0183     NULL
0184 };
0185 ATTRIBUTE_GROUPS(activity_led);
0186
0187 static int activity_activate(struct led_classdev *led_cdev)
0188 {
0189     struct activity_data *activity_data;
0190
0191     activity_data = kzalloc(sizeof(*activity_data), GFP_KERNEL);
0192     if (!activity_data)
0193         return -ENOMEM;
0194
0195     led_set_trigger_data(led_cdev, activity_data);
0196
0197     activity_data->led_cdev = led_cdev;
0198     timer_setup(&activity_data->timer, led_activity_function, 0);
0199     if (!led_cdev->blink_brightness)
0200         led_cdev->blink_brightness = led_cdev->max_brightness;
0201     led_activity_function(&activity_data->timer);
0202     set_bit(LED_BLINK_SW, &led_cdev->work_flags);
0203
0204     return 0;
0205 }
0206
0207 static void activity_deactivate(struct led_classdev *led_cdev)
0208 {
0209     struct activity_data *activity_data = led_get_trigger_data(led_cdev);
0210
0211     del_timer_sync(&activity_data->timer);
0212     kfree(activity_data);
0213     clear_bit(LED_BLINK_SW, &led_cdev->work_flags);
0214 }
0215
0216 static struct led_trigger activity_led_trigger = {
0217     .name       = "activity",
0218     .activate   = activity_activate,
0219     .deactivate = activity_deactivate,
0220     .groups     = activity_led_groups,
0221 };
0222
0223 static int activity_reboot_notifier(struct notifier_block *nb,
0224                                     unsigned long code, void *unused)
0225 {
0226     led_trigger_unregister(&activity_led_trigger);
0227     return NOTIFY_DONE;
0228 }
0229
0230 static int activity_panic_notifier(struct notifier_block *nb,
0231                                    unsigned long code, void *unused)
0232 {
0233     panic_detected = 1;
0234     return NOTIFY_DONE;
0235 }
0236
0237 static struct notifier_block activity_reboot_nb = {
0238     .notifier_call = activity_reboot_notifier,
0239 };
0240
0241 static struct notifier_block activity_panic_nb = {
0242     .notifier_call = activity_panic_notifier,
0243 };
0244
0245 static int __init activity_init(void)
0246 {
0247     int rc = led_trigger_register(&activity_led_trigger);
0248
0249     if (!rc) {
0250         atomic_notifier_chain_register(&panic_notifier_list,
0251                            &activity_panic_nb);
0252         register_reboot_notifier(&activity_reboot_nb);
0253     }
0254     return rc;
0255 }
0256
0257 static void __exit activity_exit(void)
0258 {
0259     unregister_reboot_notifier(&activity_reboot_nb);
0260     atomic_notifier_chain_unregister(&panic_notifier_list,
0261                      &activity_panic_nb);
0262     led_trigger_unregister(&activity_led_trigger);
0263 }
0264
0265 module_init(activity_init);
0266 module_exit(activity_exit);
0267
0268 MODULE_AUTHOR("Willy Tarreau <w@1wt.eu>");
0269 MODULE_DESCRIPTION("Activity LED trigger");
0270 MODULE_LICENSE("GPL v2");