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"); 269