Thomas Gleixner | 79bf2bb | 2007-02-16 01:28:03 -0800 | [diff] [blame] | 1 | /* |
| 2 | * linux/kernel/time/tick-sched.c |
| 3 | * |
| 4 | * Copyright(C) 2005-2006, Thomas Gleixner <tglx@linutronix.de> |
| 5 | * Copyright(C) 2005-2007, Red Hat, Inc., Ingo Molnar |
| 6 | * Copyright(C) 2006-2007 Timesys Corp., Thomas Gleixner |
| 7 | * |
| 8 | * No idle tick implementation for low and high resolution timers |
| 9 | * |
| 10 | * Started by: Thomas Gleixner and Ingo Molnar |
| 11 | * |
Pavel Machek | b10db7f | 2008-01-30 13:30:00 +0100 | [diff] [blame] | 12 | * Distribute under GPLv2. |
Thomas Gleixner | 79bf2bb | 2007-02-16 01:28:03 -0800 | [diff] [blame] | 13 | */ |
| 14 | #include <linux/cpu.h> |
| 15 | #include <linux/err.h> |
| 16 | #include <linux/hrtimer.h> |
| 17 | #include <linux/interrupt.h> |
| 18 | #include <linux/kernel_stat.h> |
| 19 | #include <linux/percpu.h> |
| 20 | #include <linux/profile.h> |
| 21 | #include <linux/sched.h> |
| 22 | #include <linux/tick.h> |
venkatesh.pallipadi@intel.com | 8083e4a | 2008-08-04 11:59:11 -0700 | [diff] [blame] | 23 | #include <linux/module.h> |
Thomas Gleixner | 79bf2bb | 2007-02-16 01:28:03 -0800 | [diff] [blame] | 24 | |
David S. Miller | 9e203bc | 2007-02-24 22:10:13 -0800 | [diff] [blame] | 25 | #include <asm/irq_regs.h> |
| 26 | |
Thomas Gleixner | 79bf2bb | 2007-02-16 01:28:03 -0800 | [diff] [blame] | 27 | #include "tick-internal.h" |
| 28 | |
| 29 | /* |
| 30 | * Per cpu nohz control structure |
| 31 | */ |
| 32 | static DEFINE_PER_CPU(struct tick_sched, tick_cpu_sched); |
| 33 | |
| 34 | /* |
| 35 | * The time, when the last jiffy update happened. Protected by xtime_lock. |
| 36 | */ |
| 37 | static ktime_t last_jiffies_update; |
| 38 | |
Ingo Molnar | 289f480 | 2007-02-16 01:28:15 -0800 | [diff] [blame] | 39 | struct tick_sched *tick_get_tick_sched(int cpu) |
| 40 | { |
| 41 | return &per_cpu(tick_cpu_sched, cpu); |
| 42 | } |
| 43 | |
Thomas Gleixner | 79bf2bb | 2007-02-16 01:28:03 -0800 | [diff] [blame] | 44 | /* |
| 45 | * Must be called with interrupts disabled ! |
| 46 | */ |
| 47 | static void tick_do_update_jiffies64(ktime_t now) |
| 48 | { |
| 49 | unsigned long ticks = 0; |
| 50 | ktime_t delta; |
| 51 | |
Ingo Molnar | 7a14ce1 | 2008-05-12 15:43:53 +0200 | [diff] [blame] | 52 | /* |
| 53 | * Do a quick check without holding xtime_lock: |
| 54 | */ |
| 55 | delta = ktime_sub(now, last_jiffies_update); |
| 56 | if (delta.tv64 < tick_period.tv64) |
| 57 | return; |
| 58 | |
Thomas Gleixner | 79bf2bb | 2007-02-16 01:28:03 -0800 | [diff] [blame] | 59 | /* Reevalute with xtime_lock held */ |
| 60 | write_seqlock(&xtime_lock); |
| 61 | |
| 62 | delta = ktime_sub(now, last_jiffies_update); |
| 63 | if (delta.tv64 >= tick_period.tv64) { |
| 64 | |
| 65 | delta = ktime_sub(delta, tick_period); |
| 66 | last_jiffies_update = ktime_add(last_jiffies_update, |
| 67 | tick_period); |
| 68 | |
| 69 | /* Slow path for long timeouts */ |
| 70 | if (unlikely(delta.tv64 >= tick_period.tv64)) { |
| 71 | s64 incr = ktime_to_ns(tick_period); |
| 72 | |
| 73 | ticks = ktime_divns(delta, incr); |
| 74 | |
| 75 | last_jiffies_update = ktime_add_ns(last_jiffies_update, |
| 76 | incr * ticks); |
| 77 | } |
| 78 | do_timer(++ticks); |
Thomas Gleixner | 49d670f | 2008-09-22 18:56:01 +0200 | [diff] [blame] | 79 | |
| 80 | /* Keep the tick_next_period variable up to date */ |
| 81 | tick_next_period = ktime_add(last_jiffies_update, tick_period); |
Thomas Gleixner | 79bf2bb | 2007-02-16 01:28:03 -0800 | [diff] [blame] | 82 | } |
| 83 | write_sequnlock(&xtime_lock); |
| 84 | } |
| 85 | |
| 86 | /* |
| 87 | * Initialize and return retrieve the jiffies update. |
| 88 | */ |
| 89 | static ktime_t tick_init_jiffy_update(void) |
| 90 | { |
| 91 | ktime_t period; |
| 92 | |
| 93 | write_seqlock(&xtime_lock); |
| 94 | /* Did we start the jiffies update yet ? */ |
| 95 | if (last_jiffies_update.tv64 == 0) |
| 96 | last_jiffies_update = tick_next_period; |
| 97 | period = last_jiffies_update; |
| 98 | write_sequnlock(&xtime_lock); |
| 99 | return period; |
| 100 | } |
| 101 | |
| 102 | /* |
| 103 | * NOHZ - aka dynamic tick functionality |
| 104 | */ |
| 105 | #ifdef CONFIG_NO_HZ |
| 106 | /* |
| 107 | * NO HZ enabled ? |
| 108 | */ |
| 109 | static int tick_nohz_enabled __read_mostly = 1; |
| 110 | |
| 111 | /* |
| 112 | * Enable / Disable tickless mode |
| 113 | */ |
| 114 | static int __init setup_tick_nohz(char *str) |
| 115 | { |
| 116 | if (!strcmp(str, "off")) |
| 117 | tick_nohz_enabled = 0; |
| 118 | else if (!strcmp(str, "on")) |
| 119 | tick_nohz_enabled = 1; |
| 120 | else |
| 121 | return 0; |
| 122 | return 1; |
| 123 | } |
| 124 | |
| 125 | __setup("nohz=", setup_tick_nohz); |
| 126 | |
| 127 | /** |
| 128 | * tick_nohz_update_jiffies - update jiffies when idle was interrupted |
| 129 | * |
| 130 | * Called from interrupt entry when the CPU was idle |
| 131 | * |
| 132 | * In case the sched_tick was stopped on this CPU, we have to check if jiffies |
| 133 | * must be updated. Otherwise an interrupt handler could use a stale jiffy |
| 134 | * value. We do this unconditionally on any cpu, as we don't know whether the |
| 135 | * cpu, which has the update task assigned is in a long sleep. |
| 136 | */ |
Martin Schwidefsky | eed3b9c | 2009-09-29 14:25:15 +0200 | [diff] [blame] | 137 | static void tick_nohz_update_jiffies(ktime_t now) |
Thomas Gleixner | 79bf2bb | 2007-02-16 01:28:03 -0800 | [diff] [blame] | 138 | { |
| 139 | int cpu = smp_processor_id(); |
| 140 | struct tick_sched *ts = &per_cpu(tick_cpu_sched, cpu); |
| 141 | unsigned long flags; |
Thomas Gleixner | 79bf2bb | 2007-02-16 01:28:03 -0800 | [diff] [blame] | 142 | |
Rusty Russell | 6a7b3dc | 2008-11-25 02:35:04 +1030 | [diff] [blame] | 143 | cpumask_clear_cpu(cpu, nohz_cpu_mask); |
Thomas Gleixner | 5df7fa1 | 2008-02-01 17:45:14 +0100 | [diff] [blame] | 144 | ts->idle_waketime = now; |
Thomas Gleixner | 79bf2bb | 2007-02-16 01:28:03 -0800 | [diff] [blame] | 145 | |
| 146 | local_irq_save(flags); |
| 147 | tick_do_update_jiffies64(now); |
| 148 | local_irq_restore(flags); |
Ingo Molnar | 02ff375 | 2008-05-12 15:43:53 +0200 | [diff] [blame] | 149 | |
| 150 | touch_softlockup_watchdog(); |
Thomas Gleixner | 79bf2bb | 2007-02-16 01:28:03 -0800 | [diff] [blame] | 151 | } |
| 152 | |
Arjan van de Ven | 595aac4 | 2010-05-09 08:22:45 -0700 | [diff] [blame] | 153 | /* |
| 154 | * Updates the per cpu time idle statistics counters |
| 155 | */ |
Arjan van de Ven | 8d63bf9 | 2010-05-09 08:24:03 -0700 | [diff] [blame] | 156 | static void |
Peter Zijlstra | 8c215bd | 2010-07-01 09:07:17 +0200 | [diff] [blame^] | 157 | update_ts_time_stats(int cpu, struct tick_sched *ts, ktime_t now, u64 *last_update_time) |
Arjan van de Ven | 595aac4 | 2010-05-09 08:22:45 -0700 | [diff] [blame] | 158 | { |
| 159 | ktime_t delta; |
| 160 | |
Arjan van de Ven | 595aac4 | 2010-05-09 08:22:45 -0700 | [diff] [blame] | 161 | if (ts->idle_active) { |
| 162 | delta = ktime_sub(now, ts->idle_entrytime); |
| 163 | ts->idle_sleeptime = ktime_add(ts->idle_sleeptime, delta); |
Peter Zijlstra | 8c215bd | 2010-07-01 09:07:17 +0200 | [diff] [blame^] | 164 | if (nr_iowait_cpu(cpu) > 0) |
Arjan van de Ven | 0224cf4 | 2010-05-09 08:25:23 -0700 | [diff] [blame] | 165 | ts->iowait_sleeptime = ktime_add(ts->iowait_sleeptime, delta); |
Arjan van de Ven | 8c7b09f | 2010-05-09 08:23:23 -0700 | [diff] [blame] | 166 | ts->idle_entrytime = now; |
Arjan van de Ven | 595aac4 | 2010-05-09 08:22:45 -0700 | [diff] [blame] | 167 | } |
Arjan van de Ven | 8d63bf9 | 2010-05-09 08:24:03 -0700 | [diff] [blame] | 168 | |
Arjan van de Ven | e0e37c2 | 2010-05-09 08:24:39 -0700 | [diff] [blame] | 169 | if (last_update_time) |
Arjan van de Ven | 8d63bf9 | 2010-05-09 08:24:03 -0700 | [diff] [blame] | 170 | *last_update_time = ktime_to_us(now); |
| 171 | |
Arjan van de Ven | 595aac4 | 2010-05-09 08:22:45 -0700 | [diff] [blame] | 172 | } |
| 173 | |
Martin Schwidefsky | eed3b9c | 2009-09-29 14:25:15 +0200 | [diff] [blame] | 174 | static void tick_nohz_stop_idle(int cpu, ktime_t now) |
Venki Pallipadi | 6378ddb | 2008-01-30 13:30:04 +0100 | [diff] [blame] | 175 | { |
| 176 | struct tick_sched *ts = &per_cpu(tick_cpu_sched, cpu); |
| 177 | |
Peter Zijlstra | 8c215bd | 2010-07-01 09:07:17 +0200 | [diff] [blame^] | 178 | update_ts_time_stats(cpu, ts, now, NULL); |
Martin Schwidefsky | eed3b9c | 2009-09-29 14:25:15 +0200 | [diff] [blame] | 179 | ts->idle_active = 0; |
Peter Zijlstra | 56c7426 | 2008-09-01 16:44:23 +0200 | [diff] [blame] | 180 | |
Martin Schwidefsky | eed3b9c | 2009-09-29 14:25:15 +0200 | [diff] [blame] | 181 | sched_clock_idle_wakeup_event(0); |
Venki Pallipadi | 6378ddb | 2008-01-30 13:30:04 +0100 | [diff] [blame] | 182 | } |
| 183 | |
Peter Zijlstra | 8c215bd | 2010-07-01 09:07:17 +0200 | [diff] [blame^] | 184 | static ktime_t tick_nohz_start_idle(int cpu, struct tick_sched *ts) |
Venki Pallipadi | 6378ddb | 2008-01-30 13:30:04 +0100 | [diff] [blame] | 185 | { |
Arjan van de Ven | 595aac4 | 2010-05-09 08:22:45 -0700 | [diff] [blame] | 186 | ktime_t now; |
Venki Pallipadi | 6378ddb | 2008-01-30 13:30:04 +0100 | [diff] [blame] | 187 | |
| 188 | now = ktime_get(); |
Arjan van de Ven | 595aac4 | 2010-05-09 08:22:45 -0700 | [diff] [blame] | 189 | |
Peter Zijlstra | 8c215bd | 2010-07-01 09:07:17 +0200 | [diff] [blame^] | 190 | update_ts_time_stats(cpu, ts, now, NULL); |
Arjan van de Ven | 595aac4 | 2010-05-09 08:22:45 -0700 | [diff] [blame] | 191 | |
Venki Pallipadi | 6378ddb | 2008-01-30 13:30:04 +0100 | [diff] [blame] | 192 | ts->idle_entrytime = now; |
| 193 | ts->idle_active = 1; |
Peter Zijlstra | 56c7426 | 2008-09-01 16:44:23 +0200 | [diff] [blame] | 194 | sched_clock_idle_sleep_event(); |
Venki Pallipadi | 6378ddb | 2008-01-30 13:30:04 +0100 | [diff] [blame] | 195 | return now; |
| 196 | } |
| 197 | |
Arjan van de Ven | b1f724c | 2010-05-09 08:22:08 -0700 | [diff] [blame] | 198 | /** |
| 199 | * get_cpu_idle_time_us - get the total idle time of a cpu |
| 200 | * @cpu: CPU number to query |
| 201 | * @last_update_time: variable to store update time in |
| 202 | * |
| 203 | * Return the cummulative idle time (since boot) for a given |
| 204 | * CPU, in microseconds. The idle time returned includes |
| 205 | * the iowait time (unlike what "top" and co report). |
| 206 | * |
| 207 | * This time is measured via accounting rather than sampling, |
| 208 | * and is as accurate as ktime_get() is. |
| 209 | * |
| 210 | * This function returns -1 if NOHZ is not enabled. |
| 211 | */ |
Venki Pallipadi | 6378ddb | 2008-01-30 13:30:04 +0100 | [diff] [blame] | 212 | u64 get_cpu_idle_time_us(int cpu, u64 *last_update_time) |
| 213 | { |
| 214 | struct tick_sched *ts = &per_cpu(tick_cpu_sched, cpu); |
| 215 | |
venkatesh.pallipadi@intel.com | 8083e4a | 2008-08-04 11:59:11 -0700 | [diff] [blame] | 216 | if (!tick_nohz_enabled) |
| 217 | return -1; |
| 218 | |
Peter Zijlstra | 8c215bd | 2010-07-01 09:07:17 +0200 | [diff] [blame^] | 219 | update_ts_time_stats(cpu, ts, ktime_get(), last_update_time); |
venkatesh.pallipadi@intel.com | 8083e4a | 2008-08-04 11:59:11 -0700 | [diff] [blame] | 220 | |
Venki Pallipadi | 6378ddb | 2008-01-30 13:30:04 +0100 | [diff] [blame] | 221 | return ktime_to_us(ts->idle_sleeptime); |
| 222 | } |
venkatesh.pallipadi@intel.com | 8083e4a | 2008-08-04 11:59:11 -0700 | [diff] [blame] | 223 | EXPORT_SYMBOL_GPL(get_cpu_idle_time_us); |
Venki Pallipadi | 6378ddb | 2008-01-30 13:30:04 +0100 | [diff] [blame] | 224 | |
Arjan van de Ven | 0224cf4 | 2010-05-09 08:25:23 -0700 | [diff] [blame] | 225 | /* |
| 226 | * get_cpu_iowait_time_us - get the total iowait time of a cpu |
| 227 | * @cpu: CPU number to query |
| 228 | * @last_update_time: variable to store update time in |
| 229 | * |
| 230 | * Return the cummulative iowait time (since boot) for a given |
| 231 | * CPU, in microseconds. |
| 232 | * |
| 233 | * This time is measured via accounting rather than sampling, |
| 234 | * and is as accurate as ktime_get() is. |
| 235 | * |
| 236 | * This function returns -1 if NOHZ is not enabled. |
| 237 | */ |
| 238 | u64 get_cpu_iowait_time_us(int cpu, u64 *last_update_time) |
| 239 | { |
| 240 | struct tick_sched *ts = &per_cpu(tick_cpu_sched, cpu); |
| 241 | |
| 242 | if (!tick_nohz_enabled) |
| 243 | return -1; |
| 244 | |
Peter Zijlstra | 8c215bd | 2010-07-01 09:07:17 +0200 | [diff] [blame^] | 245 | update_ts_time_stats(cpu, ts, ktime_get(), last_update_time); |
Arjan van de Ven | 0224cf4 | 2010-05-09 08:25:23 -0700 | [diff] [blame] | 246 | |
| 247 | return ktime_to_us(ts->iowait_sleeptime); |
| 248 | } |
| 249 | EXPORT_SYMBOL_GPL(get_cpu_iowait_time_us); |
| 250 | |
Thomas Gleixner | 79bf2bb | 2007-02-16 01:28:03 -0800 | [diff] [blame] | 251 | /** |
| 252 | * tick_nohz_stop_sched_tick - stop the idle tick from the idle task |
| 253 | * |
| 254 | * When the next event is more than a tick into the future, stop the idle tick |
| 255 | * Called either from the idle loop or from irq_exit() when an idle period was |
| 256 | * just interrupted by an interrupt which did not cause a reschedule. |
| 257 | */ |
Thomas Gleixner | b8f8c3c | 2008-07-18 17:27:28 +0200 | [diff] [blame] | 258 | void tick_nohz_stop_sched_tick(int inidle) |
Thomas Gleixner | 79bf2bb | 2007-02-16 01:28:03 -0800 | [diff] [blame] | 259 | { |
| 260 | unsigned long seq, last_jiffies, next_jiffies, delta_jiffies, flags; |
| 261 | struct tick_sched *ts; |
Venki Pallipadi | 6378ddb | 2008-01-30 13:30:04 +0100 | [diff] [blame] | 262 | ktime_t last_update, expires, now; |
Len Brown | 4f86d3a | 2007-10-03 18:58:00 -0400 | [diff] [blame] | 263 | struct clock_event_device *dev = __get_cpu_var(tick_cpu_device).evtdev; |
Jon Hunter | 9896246 | 2009-08-18 12:45:10 -0500 | [diff] [blame] | 264 | u64 time_delta; |
Thomas Gleixner | 79bf2bb | 2007-02-16 01:28:03 -0800 | [diff] [blame] | 265 | int cpu; |
| 266 | |
| 267 | local_irq_save(flags); |
| 268 | |
| 269 | cpu = smp_processor_id(); |
| 270 | ts = &per_cpu(tick_cpu_sched, cpu); |
Eero Nurkkala | f2e21c9 | 2009-05-25 09:57:37 +0300 | [diff] [blame] | 271 | |
| 272 | /* |
| 273 | * Call to tick_nohz_start_idle stops the last_update_time from being |
| 274 | * updated. Thus, it must not be called in the event we are called from |
| 275 | * irq_exit() with the prior state different than idle. |
| 276 | */ |
| 277 | if (!inidle && !ts->inidle) |
| 278 | goto end; |
| 279 | |
Eero Nurkkala | fdc6f19 | 2009-10-07 11:54:26 +0300 | [diff] [blame] | 280 | /* |
| 281 | * Set ts->inidle unconditionally. Even if the system did not |
| 282 | * switch to NOHZ mode the cpu frequency governers rely on the |
| 283 | * update of the idle time accounting in tick_nohz_start_idle(). |
| 284 | */ |
| 285 | ts->inidle = 1; |
| 286 | |
Peter Zijlstra | 8c215bd | 2010-07-01 09:07:17 +0200 | [diff] [blame^] | 287 | now = tick_nohz_start_idle(cpu, ts); |
Thomas Gleixner | 79bf2bb | 2007-02-16 01:28:03 -0800 | [diff] [blame] | 288 | |
Thomas Gleixner | 5e41d0d | 2007-09-16 15:36:43 +0200 | [diff] [blame] | 289 | /* |
| 290 | * If this cpu is offline and it is the one which updates |
| 291 | * jiffies, then give up the assignment and let it be taken by |
| 292 | * the cpu which runs the tick timer next. If we don't drop |
| 293 | * this here the jiffies might be stale and do_timer() never |
| 294 | * invoked. |
| 295 | */ |
| 296 | if (unlikely(!cpu_online(cpu))) { |
| 297 | if (cpu == tick_do_timer_cpu) |
Thomas Gleixner | 6441402 | 2008-09-22 18:46:37 +0200 | [diff] [blame] | 298 | tick_do_timer_cpu = TICK_DO_TIMER_NONE; |
Thomas Gleixner | 5e41d0d | 2007-09-16 15:36:43 +0200 | [diff] [blame] | 299 | } |
| 300 | |
Thomas Gleixner | 79bf2bb | 2007-02-16 01:28:03 -0800 | [diff] [blame] | 301 | if (unlikely(ts->nohz_mode == NOHZ_MODE_INACTIVE)) |
| 302 | goto end; |
| 303 | |
| 304 | if (need_resched()) |
| 305 | goto end; |
| 306 | |
Heiko Carstens | fa116ea | 2008-12-11 17:04:11 +0100 | [diff] [blame] | 307 | if (unlikely(local_softirq_pending() && cpu_online(cpu))) { |
Thomas Gleixner | 3528231 | 2007-05-23 13:57:37 -0700 | [diff] [blame] | 308 | static int ratelimit; |
| 309 | |
| 310 | if (ratelimit < 10) { |
| 311 | printk(KERN_ERR "NOHZ: local_softirq_pending %02x\n", |
Thomas Gleixner | 529eacc | 2009-11-13 14:32:19 +0100 | [diff] [blame] | 312 | (unsigned int) local_softirq_pending()); |
Thomas Gleixner | 3528231 | 2007-05-23 13:57:37 -0700 | [diff] [blame] | 313 | ratelimit++; |
| 314 | } |
Heiko Carstens | 857f3fd | 2008-07-11 11:09:22 +0200 | [diff] [blame] | 315 | goto end; |
Thomas Gleixner | 3528231 | 2007-05-23 13:57:37 -0700 | [diff] [blame] | 316 | } |
Thomas Gleixner | 79bf2bb | 2007-02-16 01:28:03 -0800 | [diff] [blame] | 317 | |
Mike Galbraith | 39c0cbe | 2010-03-11 17:17:13 +0100 | [diff] [blame] | 318 | if (nohz_ratelimit(cpu)) |
| 319 | goto end; |
| 320 | |
Thomas Gleixner | 79bf2bb | 2007-02-16 01:28:03 -0800 | [diff] [blame] | 321 | ts->idle_calls++; |
Thomas Gleixner | 79bf2bb | 2007-02-16 01:28:03 -0800 | [diff] [blame] | 322 | /* Read jiffies and the time when jiffies were updated last */ |
| 323 | do { |
| 324 | seq = read_seqbegin(&xtime_lock); |
| 325 | last_update = last_jiffies_update; |
| 326 | last_jiffies = jiffies; |
Thomas Gleixner | 2718501 | 2009-11-12 22:12:06 +0100 | [diff] [blame] | 327 | time_delta = timekeeping_max_deferment(); |
Thomas Gleixner | 79bf2bb | 2007-02-16 01:28:03 -0800 | [diff] [blame] | 328 | } while (read_seqretry(&xtime_lock, seq)); |
| 329 | |
Martin Schwidefsky | 3c5d92a | 2009-09-29 14:25:16 +0200 | [diff] [blame] | 330 | if (rcu_needs_cpu(cpu) || printk_needs_cpu(cpu) || |
| 331 | arch_needs_cpu(cpu)) { |
| 332 | next_jiffies = last_jiffies + 1; |
Ingo Molnar | 6ba9b34 | 2007-02-19 18:11:56 +0000 | [diff] [blame] | 333 | delta_jiffies = 1; |
Martin Schwidefsky | 3c5d92a | 2009-09-29 14:25:16 +0200 | [diff] [blame] | 334 | } else { |
| 335 | /* Get the next timer wheel timer */ |
| 336 | next_jiffies = get_next_timer_interrupt(last_jiffies); |
| 337 | delta_jiffies = next_jiffies - last_jiffies; |
| 338 | } |
Thomas Gleixner | 79bf2bb | 2007-02-16 01:28:03 -0800 | [diff] [blame] | 339 | /* |
| 340 | * Do not stop the tick, if we are only one off |
| 341 | * or if the cpu is required for rcu |
| 342 | */ |
Ingo Molnar | 6ba9b34 | 2007-02-19 18:11:56 +0000 | [diff] [blame] | 343 | if (!ts->tick_stopped && delta_jiffies == 1) |
Thomas Gleixner | 79bf2bb | 2007-02-16 01:28:03 -0800 | [diff] [blame] | 344 | goto out; |
| 345 | |
| 346 | /* Schedule the tick, if we are at least one jiffie off */ |
| 347 | if ((long)delta_jiffies >= 1) { |
| 348 | |
Woodruff, Richard | 0014744 | 2008-12-01 14:18:11 -0800 | [diff] [blame] | 349 | /* |
Woodruff, Richard | 0014744 | 2008-12-01 14:18:11 -0800 | [diff] [blame] | 350 | * If this cpu is the one which updates jiffies, then |
| 351 | * give up the assignment and let it be taken by the |
| 352 | * cpu which runs the tick timer next, which might be |
| 353 | * this cpu as well. If we don't drop this here the |
| 354 | * jiffies might be stale and do_timer() never |
Thomas Gleixner | 2718501 | 2009-11-12 22:12:06 +0100 | [diff] [blame] | 355 | * invoked. Keep track of the fact that it was the one |
| 356 | * which had the do_timer() duty last. If this cpu is |
| 357 | * the one which had the do_timer() duty last, we |
| 358 | * limit the sleep time to the timekeeping |
| 359 | * max_deferement value which we retrieved |
| 360 | * above. Otherwise we can sleep as long as we want. |
Woodruff, Richard | 0014744 | 2008-12-01 14:18:11 -0800 | [diff] [blame] | 361 | */ |
Thomas Gleixner | 2718501 | 2009-11-12 22:12:06 +0100 | [diff] [blame] | 362 | if (cpu == tick_do_timer_cpu) { |
Woodruff, Richard | 0014744 | 2008-12-01 14:18:11 -0800 | [diff] [blame] | 363 | tick_do_timer_cpu = TICK_DO_TIMER_NONE; |
Thomas Gleixner | 2718501 | 2009-11-12 22:12:06 +0100 | [diff] [blame] | 364 | ts->do_timer_last = 1; |
| 365 | } else if (tick_do_timer_cpu != TICK_DO_TIMER_NONE) { |
| 366 | time_delta = KTIME_MAX; |
| 367 | ts->do_timer_last = 0; |
| 368 | } else if (!ts->do_timer_last) { |
| 369 | time_delta = KTIME_MAX; |
| 370 | } |
| 371 | |
| 372 | /* |
Jon Hunter | 9896246 | 2009-08-18 12:45:10 -0500 | [diff] [blame] | 373 | * calculate the expiry time for the next timer wheel |
| 374 | * timer. delta_jiffies >= NEXT_TIMER_MAX_DELTA signals |
| 375 | * that there is no timer pending or at least extremely |
| 376 | * far into the future (12 days for HZ=1000). In this |
| 377 | * case we set the expiry to the end of time. |
| 378 | */ |
| 379 | if (likely(delta_jiffies < NEXT_TIMER_MAX_DELTA)) { |
| 380 | /* |
| 381 | * Calculate the time delta for the next timer event. |
| 382 | * If the time delta exceeds the maximum time delta |
| 383 | * permitted by the current clocksource then adjust |
| 384 | * the time delta accordingly to ensure the |
| 385 | * clocksource does not wrap. |
| 386 | */ |
| 387 | time_delta = min_t(u64, time_delta, |
| 388 | tick_period.tv64 * delta_jiffies); |
Jon Hunter | 9896246 | 2009-08-18 12:45:10 -0500 | [diff] [blame] | 389 | } |
Woodruff, Richard | 0014744 | 2008-12-01 14:18:11 -0800 | [diff] [blame] | 390 | |
Thomas Gleixner | 2718501 | 2009-11-12 22:12:06 +0100 | [diff] [blame] | 391 | if (time_delta < KTIME_MAX) |
| 392 | expires = ktime_add_ns(last_update, time_delta); |
| 393 | else |
| 394 | expires.tv64 = KTIME_MAX; |
Woodruff, Richard | 0014744 | 2008-12-01 14:18:11 -0800 | [diff] [blame] | 395 | |
Ingo Molnar | 6ba9b34 | 2007-02-19 18:11:56 +0000 | [diff] [blame] | 396 | if (delta_jiffies > 1) |
Rusty Russell | 6a7b3dc | 2008-11-25 02:35:04 +1030 | [diff] [blame] | 397 | cpumask_set_cpu(cpu, nohz_cpu_mask); |
Woodruff, Richard | 0014744 | 2008-12-01 14:18:11 -0800 | [diff] [blame] | 398 | |
| 399 | /* Skip reprogram of event if its not changed */ |
| 400 | if (ts->tick_stopped && ktime_equal(expires, dev->next_event)) |
| 401 | goto out; |
| 402 | |
Thomas Gleixner | 79bf2bb | 2007-02-16 01:28:03 -0800 | [diff] [blame] | 403 | /* |
| 404 | * nohz_stop_sched_tick can be called several times before |
| 405 | * the nohz_restart_sched_tick is called. This happens when |
| 406 | * interrupts arrive which do not cause a reschedule. In the |
| 407 | * first call we save the current tick time, so we can restart |
| 408 | * the scheduler tick in nohz_restart_sched_tick. |
| 409 | */ |
| 410 | if (!ts->tick_stopped) { |
Siddha, Suresh B | 46cb4b7 | 2007-05-08 00:32:51 -0700 | [diff] [blame] | 411 | if (select_nohz_load_balancer(1)) { |
| 412 | /* |
| 413 | * sched tick not stopped! |
| 414 | */ |
Rusty Russell | 6a7b3dc | 2008-11-25 02:35:04 +1030 | [diff] [blame] | 415 | cpumask_clear_cpu(cpu, nohz_cpu_mask); |
Siddha, Suresh B | 46cb4b7 | 2007-05-08 00:32:51 -0700 | [diff] [blame] | 416 | goto out; |
| 417 | } |
| 418 | |
Arjan van de Ven | cc584b2 | 2008-09-01 15:02:30 -0700 | [diff] [blame] | 419 | ts->idle_tick = hrtimer_get_expires(&ts->sched_timer); |
Thomas Gleixner | 79bf2bb | 2007-02-16 01:28:03 -0800 | [diff] [blame] | 420 | ts->tick_stopped = 1; |
| 421 | ts->idle_jiffies = last_jiffies; |
Steven Rostedt | 2232c2d | 2008-02-29 18:46:50 +0100 | [diff] [blame] | 422 | rcu_enter_nohz(); |
Thomas Gleixner | 79bf2bb | 2007-02-16 01:28:03 -0800 | [diff] [blame] | 423 | } |
Thomas Gleixner | d3ed782 | 2007-05-08 00:30:03 -0700 | [diff] [blame] | 424 | |
Thomas Gleixner | eaad084 | 2007-05-29 23:47:39 +0200 | [diff] [blame] | 425 | ts->idle_sleeps++; |
| 426 | |
Jon Hunter | 9896246 | 2009-08-18 12:45:10 -0500 | [diff] [blame] | 427 | /* Mark expires */ |
| 428 | ts->idle_expires = expires; |
| 429 | |
Thomas Gleixner | eaad084 | 2007-05-29 23:47:39 +0200 | [diff] [blame] | 430 | /* |
Jon Hunter | 9896246 | 2009-08-18 12:45:10 -0500 | [diff] [blame] | 431 | * If the expiration time == KTIME_MAX, then |
| 432 | * in this case we simply stop the tick timer. |
Thomas Gleixner | eaad084 | 2007-05-29 23:47:39 +0200 | [diff] [blame] | 433 | */ |
Jon Hunter | 9896246 | 2009-08-18 12:45:10 -0500 | [diff] [blame] | 434 | if (unlikely(expires.tv64 == KTIME_MAX)) { |
Thomas Gleixner | eaad084 | 2007-05-29 23:47:39 +0200 | [diff] [blame] | 435 | if (ts->nohz_mode == NOHZ_MODE_HIGHRES) |
| 436 | hrtimer_cancel(&ts->sched_timer); |
| 437 | goto out; |
| 438 | } |
| 439 | |
Thomas Gleixner | 79bf2bb | 2007-02-16 01:28:03 -0800 | [diff] [blame] | 440 | if (ts->nohz_mode == NOHZ_MODE_HIGHRES) { |
| 441 | hrtimer_start(&ts->sched_timer, expires, |
Arun R Bharadwaj | 5c33386 | 2009-04-16 12:14:37 +0530 | [diff] [blame] | 442 | HRTIMER_MODE_ABS_PINNED); |
Thomas Gleixner | 79bf2bb | 2007-02-16 01:28:03 -0800 | [diff] [blame] | 443 | /* Check, if the timer was already in the past */ |
| 444 | if (hrtimer_active(&ts->sched_timer)) |
| 445 | goto out; |
Pavel Machek | 4c9dc64 | 2008-01-30 13:30:00 +0100 | [diff] [blame] | 446 | } else if (!tick_program_event(expires, 0)) |
Thomas Gleixner | 79bf2bb | 2007-02-16 01:28:03 -0800 | [diff] [blame] | 447 | goto out; |
| 448 | /* |
| 449 | * We are past the event already. So we crossed a |
| 450 | * jiffie boundary. Update jiffies and raise the |
| 451 | * softirq. |
| 452 | */ |
| 453 | tick_do_update_jiffies64(ktime_get()); |
Rusty Russell | 6a7b3dc | 2008-11-25 02:35:04 +1030 | [diff] [blame] | 454 | cpumask_clear_cpu(cpu, nohz_cpu_mask); |
Thomas Gleixner | 79bf2bb | 2007-02-16 01:28:03 -0800 | [diff] [blame] | 455 | } |
| 456 | raise_softirq_irqoff(TIMER_SOFTIRQ); |
| 457 | out: |
| 458 | ts->next_jiffies = next_jiffies; |
| 459 | ts->last_jiffies = last_jiffies; |
Len Brown | 4f86d3a | 2007-10-03 18:58:00 -0400 | [diff] [blame] | 460 | ts->sleep_length = ktime_sub(dev->next_event, now); |
Thomas Gleixner | 79bf2bb | 2007-02-16 01:28:03 -0800 | [diff] [blame] | 461 | end: |
| 462 | local_irq_restore(flags); |
| 463 | } |
| 464 | |
| 465 | /** |
Len Brown | 4f86d3a | 2007-10-03 18:58:00 -0400 | [diff] [blame] | 466 | * tick_nohz_get_sleep_length - return the length of the current sleep |
| 467 | * |
| 468 | * Called from power state control code with interrupts disabled |
| 469 | */ |
| 470 | ktime_t tick_nohz_get_sleep_length(void) |
| 471 | { |
| 472 | struct tick_sched *ts = &__get_cpu_var(tick_cpu_sched); |
| 473 | |
| 474 | return ts->sleep_length; |
| 475 | } |
| 476 | |
Thomas Gleixner | c34bec5 | 2008-10-17 10:04:34 +0200 | [diff] [blame] | 477 | static void tick_nohz_restart(struct tick_sched *ts, ktime_t now) |
| 478 | { |
| 479 | hrtimer_cancel(&ts->sched_timer); |
Thomas Gleixner | 268a3dc | 2008-10-22 09:48:06 +0200 | [diff] [blame] | 480 | hrtimer_set_expires(&ts->sched_timer, ts->idle_tick); |
Thomas Gleixner | c34bec5 | 2008-10-17 10:04:34 +0200 | [diff] [blame] | 481 | |
| 482 | while (1) { |
| 483 | /* Forward the time to expire in the future */ |
| 484 | hrtimer_forward(&ts->sched_timer, now, tick_period); |
| 485 | |
| 486 | if (ts->nohz_mode == NOHZ_MODE_HIGHRES) { |
Thomas Gleixner | 268a3dc | 2008-10-22 09:48:06 +0200 | [diff] [blame] | 487 | hrtimer_start_expires(&ts->sched_timer, |
Arun R Bharadwaj | 5c33386 | 2009-04-16 12:14:37 +0530 | [diff] [blame] | 488 | HRTIMER_MODE_ABS_PINNED); |
Thomas Gleixner | c34bec5 | 2008-10-17 10:04:34 +0200 | [diff] [blame] | 489 | /* Check, if the timer was already in the past */ |
| 490 | if (hrtimer_active(&ts->sched_timer)) |
| 491 | break; |
| 492 | } else { |
Thomas Gleixner | 268a3dc | 2008-10-22 09:48:06 +0200 | [diff] [blame] | 493 | if (!tick_program_event( |
| 494 | hrtimer_get_expires(&ts->sched_timer), 0)) |
Thomas Gleixner | c34bec5 | 2008-10-17 10:04:34 +0200 | [diff] [blame] | 495 | break; |
| 496 | } |
| 497 | /* Update jiffies and reread time */ |
| 498 | tick_do_update_jiffies64(now); |
| 499 | now = ktime_get(); |
| 500 | } |
| 501 | } |
| 502 | |
Len Brown | 4f86d3a | 2007-10-03 18:58:00 -0400 | [diff] [blame] | 503 | /** |
Li Zefan | 8dce39c | 2007-11-05 14:51:10 -0800 | [diff] [blame] | 504 | * tick_nohz_restart_sched_tick - restart the idle tick from the idle task |
Thomas Gleixner | 79bf2bb | 2007-02-16 01:28:03 -0800 | [diff] [blame] | 505 | * |
| 506 | * Restart the idle tick when the CPU is woken up from idle |
| 507 | */ |
| 508 | void tick_nohz_restart_sched_tick(void) |
| 509 | { |
| 510 | int cpu = smp_processor_id(); |
| 511 | struct tick_sched *ts = &per_cpu(tick_cpu_sched, cpu); |
Martin Schwidefsky | 79741dd | 2008-12-31 15:11:38 +0100 | [diff] [blame] | 512 | #ifndef CONFIG_VIRT_CPU_ACCOUNTING |
Thomas Gleixner | 79bf2bb | 2007-02-16 01:28:03 -0800 | [diff] [blame] | 513 | unsigned long ticks; |
Martin Schwidefsky | 79741dd | 2008-12-31 15:11:38 +0100 | [diff] [blame] | 514 | #endif |
Venki Pallipadi | 6378ddb | 2008-01-30 13:30:04 +0100 | [diff] [blame] | 515 | ktime_t now; |
Thomas Gleixner | 79bf2bb | 2007-02-16 01:28:03 -0800 | [diff] [blame] | 516 | |
| 517 | local_irq_disable(); |
Martin Schwidefsky | eed3b9c | 2009-09-29 14:25:15 +0200 | [diff] [blame] | 518 | if (ts->idle_active || (ts->inidle && ts->tick_stopped)) |
| 519 | now = ktime_get(); |
| 520 | |
| 521 | if (ts->idle_active) |
| 522 | tick_nohz_stop_idle(cpu, now); |
Venki Pallipadi | 6378ddb | 2008-01-30 13:30:04 +0100 | [diff] [blame] | 523 | |
Thomas Gleixner | b8f8c3c | 2008-07-18 17:27:28 +0200 | [diff] [blame] | 524 | if (!ts->inidle || !ts->tick_stopped) { |
| 525 | ts->inidle = 0; |
Venki Pallipadi | 6378ddb | 2008-01-30 13:30:04 +0100 | [diff] [blame] | 526 | local_irq_enable(); |
| 527 | return; |
| 528 | } |
| 529 | |
Thomas Gleixner | b8f8c3c | 2008-07-18 17:27:28 +0200 | [diff] [blame] | 530 | ts->inidle = 0; |
| 531 | |
Steven Rostedt | 2232c2d | 2008-02-29 18:46:50 +0100 | [diff] [blame] | 532 | rcu_exit_nohz(); |
| 533 | |
Venki Pallipadi | 6378ddb | 2008-01-30 13:30:04 +0100 | [diff] [blame] | 534 | /* Update jiffies first */ |
Siddha, Suresh B | 46cb4b7 | 2007-05-08 00:32:51 -0700 | [diff] [blame] | 535 | select_nohz_load_balancer(0); |
Thomas Gleixner | 79bf2bb | 2007-02-16 01:28:03 -0800 | [diff] [blame] | 536 | tick_do_update_jiffies64(now); |
Rusty Russell | 6a7b3dc | 2008-11-25 02:35:04 +1030 | [diff] [blame] | 537 | cpumask_clear_cpu(cpu, nohz_cpu_mask); |
Thomas Gleixner | 79bf2bb | 2007-02-16 01:28:03 -0800 | [diff] [blame] | 538 | |
Martin Schwidefsky | 79741dd | 2008-12-31 15:11:38 +0100 | [diff] [blame] | 539 | #ifndef CONFIG_VIRT_CPU_ACCOUNTING |
Thomas Gleixner | 79bf2bb | 2007-02-16 01:28:03 -0800 | [diff] [blame] | 540 | /* |
| 541 | * We stopped the tick in idle. Update process times would miss the |
| 542 | * time we slept as update_process_times does only a 1 tick |
| 543 | * accounting. Enforce that this is accounted to idle ! |
| 544 | */ |
| 545 | ticks = jiffies - ts->idle_jiffies; |
| 546 | /* |
| 547 | * We might be one off. Do not randomly account a huge number of ticks! |
| 548 | */ |
Martin Schwidefsky | 79741dd | 2008-12-31 15:11:38 +0100 | [diff] [blame] | 549 | if (ticks && ticks < LONG_MAX) |
| 550 | account_idle_ticks(ticks); |
| 551 | #endif |
Thomas Gleixner | 79bf2bb | 2007-02-16 01:28:03 -0800 | [diff] [blame] | 552 | |
Ingo Molnar | 126e01b | 2008-04-25 00:25:08 +0200 | [diff] [blame] | 553 | touch_softlockup_watchdog(); |
Thomas Gleixner | 79bf2bb | 2007-02-16 01:28:03 -0800 | [diff] [blame] | 554 | /* |
| 555 | * Cancel the scheduled timer and restore the tick |
| 556 | */ |
| 557 | ts->tick_stopped = 0; |
Thomas Gleixner | 5df7fa1 | 2008-02-01 17:45:14 +0100 | [diff] [blame] | 558 | ts->idle_exittime = now; |
Thomas Gleixner | 79bf2bb | 2007-02-16 01:28:03 -0800 | [diff] [blame] | 559 | |
Thomas Gleixner | c34bec5 | 2008-10-17 10:04:34 +0200 | [diff] [blame] | 560 | tick_nohz_restart(ts, now); |
Thomas Gleixner | 79bf2bb | 2007-02-16 01:28:03 -0800 | [diff] [blame] | 561 | |
Thomas Gleixner | 79bf2bb | 2007-02-16 01:28:03 -0800 | [diff] [blame] | 562 | local_irq_enable(); |
| 563 | } |
| 564 | |
| 565 | static int tick_nohz_reprogram(struct tick_sched *ts, ktime_t now) |
| 566 | { |
| 567 | hrtimer_forward(&ts->sched_timer, now, tick_period); |
Arjan van de Ven | cc584b2 | 2008-09-01 15:02:30 -0700 | [diff] [blame] | 568 | return tick_program_event(hrtimer_get_expires(&ts->sched_timer), 0); |
Thomas Gleixner | 79bf2bb | 2007-02-16 01:28:03 -0800 | [diff] [blame] | 569 | } |
| 570 | |
| 571 | /* |
| 572 | * The nohz low res interrupt handler |
| 573 | */ |
| 574 | static void tick_nohz_handler(struct clock_event_device *dev) |
| 575 | { |
| 576 | struct tick_sched *ts = &__get_cpu_var(tick_cpu_sched); |
| 577 | struct pt_regs *regs = get_irq_regs(); |
Thomas Gleixner | d3ed782 | 2007-05-08 00:30:03 -0700 | [diff] [blame] | 578 | int cpu = smp_processor_id(); |
Thomas Gleixner | 79bf2bb | 2007-02-16 01:28:03 -0800 | [diff] [blame] | 579 | ktime_t now = ktime_get(); |
| 580 | |
| 581 | dev->next_event.tv64 = KTIME_MAX; |
| 582 | |
Thomas Gleixner | d3ed782 | 2007-05-08 00:30:03 -0700 | [diff] [blame] | 583 | /* |
| 584 | * Check if the do_timer duty was dropped. We don't care about |
| 585 | * concurrency: This happens only when the cpu in charge went |
| 586 | * into a long sleep. If two cpus happen to assign themself to |
| 587 | * this duty, then the jiffies update is still serialized by |
| 588 | * xtime_lock. |
| 589 | */ |
Thomas Gleixner | 6441402 | 2008-09-22 18:46:37 +0200 | [diff] [blame] | 590 | if (unlikely(tick_do_timer_cpu == TICK_DO_TIMER_NONE)) |
Thomas Gleixner | d3ed782 | 2007-05-08 00:30:03 -0700 | [diff] [blame] | 591 | tick_do_timer_cpu = cpu; |
| 592 | |
Thomas Gleixner | 79bf2bb | 2007-02-16 01:28:03 -0800 | [diff] [blame] | 593 | /* Check, if the jiffies need an update */ |
Thomas Gleixner | d3ed782 | 2007-05-08 00:30:03 -0700 | [diff] [blame] | 594 | if (tick_do_timer_cpu == cpu) |
| 595 | tick_do_update_jiffies64(now); |
Thomas Gleixner | 79bf2bb | 2007-02-16 01:28:03 -0800 | [diff] [blame] | 596 | |
| 597 | /* |
| 598 | * When we are idle and the tick is stopped, we have to touch |
| 599 | * the watchdog as we might not schedule for a really long |
| 600 | * time. This happens on complete idle SMP systems while |
| 601 | * waiting on the login prompt. We also increment the "start |
| 602 | * of idle" jiffy stamp so the idle accounting adjustment we |
| 603 | * do when we go busy again does not account too much ticks. |
| 604 | */ |
| 605 | if (ts->tick_stopped) { |
| 606 | touch_softlockup_watchdog(); |
| 607 | ts->idle_jiffies++; |
| 608 | } |
| 609 | |
| 610 | update_process_times(user_mode(regs)); |
| 611 | profile_tick(CPU_PROFILING); |
| 612 | |
Thomas Gleixner | 79bf2bb | 2007-02-16 01:28:03 -0800 | [diff] [blame] | 613 | while (tick_nohz_reprogram(ts, now)) { |
| 614 | now = ktime_get(); |
| 615 | tick_do_update_jiffies64(now); |
| 616 | } |
| 617 | } |
| 618 | |
| 619 | /** |
| 620 | * tick_nohz_switch_to_nohz - switch to nohz mode |
| 621 | */ |
| 622 | static void tick_nohz_switch_to_nohz(void) |
| 623 | { |
| 624 | struct tick_sched *ts = &__get_cpu_var(tick_cpu_sched); |
| 625 | ktime_t next; |
| 626 | |
| 627 | if (!tick_nohz_enabled) |
| 628 | return; |
| 629 | |
| 630 | local_irq_disable(); |
| 631 | if (tick_switch_to_oneshot(tick_nohz_handler)) { |
| 632 | local_irq_enable(); |
| 633 | return; |
| 634 | } |
| 635 | |
| 636 | ts->nohz_mode = NOHZ_MODE_LOWRES; |
| 637 | |
| 638 | /* |
| 639 | * Recycle the hrtimer in ts, so we can share the |
| 640 | * hrtimer_forward with the highres code. |
| 641 | */ |
| 642 | hrtimer_init(&ts->sched_timer, CLOCK_MONOTONIC, HRTIMER_MODE_ABS); |
| 643 | /* Get the next period */ |
| 644 | next = tick_init_jiffy_update(); |
| 645 | |
| 646 | for (;;) { |
Arjan van de Ven | cc584b2 | 2008-09-01 15:02:30 -0700 | [diff] [blame] | 647 | hrtimer_set_expires(&ts->sched_timer, next); |
Thomas Gleixner | 79bf2bb | 2007-02-16 01:28:03 -0800 | [diff] [blame] | 648 | if (!tick_program_event(next, 0)) |
| 649 | break; |
| 650 | next = ktime_add(next, tick_period); |
| 651 | } |
| 652 | local_irq_enable(); |
| 653 | |
| 654 | printk(KERN_INFO "Switched to NOHz mode on CPU #%d\n", |
| 655 | smp_processor_id()); |
| 656 | } |
| 657 | |
Thomas Gleixner | fb02fbc | 2008-10-17 10:01:23 +0200 | [diff] [blame] | 658 | /* |
| 659 | * When NOHZ is enabled and the tick is stopped, we need to kick the |
| 660 | * tick timer from irq_enter() so that the jiffies update is kept |
| 661 | * alive during long running softirqs. That's ugly as hell, but |
| 662 | * correctness is key even if we need to fix the offending softirq in |
| 663 | * the first place. |
| 664 | * |
| 665 | * Note, this is different to tick_nohz_restart. We just kick the |
| 666 | * timer and do not touch the other magic bits which need to be done |
| 667 | * when idle is left. |
| 668 | */ |
Martin Schwidefsky | eed3b9c | 2009-09-29 14:25:15 +0200 | [diff] [blame] | 669 | static void tick_nohz_kick_tick(int cpu, ktime_t now) |
Thomas Gleixner | fb02fbc | 2008-10-17 10:01:23 +0200 | [diff] [blame] | 670 | { |
Thomas Gleixner | ae99286 | 2008-11-10 13:20:23 +0100 | [diff] [blame] | 671 | #if 0 |
| 672 | /* Switch back to 2.6.27 behaviour */ |
| 673 | |
Thomas Gleixner | fb02fbc | 2008-10-17 10:01:23 +0200 | [diff] [blame] | 674 | struct tick_sched *ts = &per_cpu(tick_cpu_sched, cpu); |
Martin Schwidefsky | eed3b9c | 2009-09-29 14:25:15 +0200 | [diff] [blame] | 675 | ktime_t delta; |
Thomas Gleixner | fb02fbc | 2008-10-17 10:01:23 +0200 | [diff] [blame] | 676 | |
Thomas Gleixner | c4bd822 | 2008-10-21 20:17:35 +0200 | [diff] [blame] | 677 | /* |
| 678 | * Do not touch the tick device, when the next expiry is either |
| 679 | * already reached or less/equal than the tick period. |
| 680 | */ |
Thomas Gleixner | 268a3dc | 2008-10-22 09:48:06 +0200 | [diff] [blame] | 681 | delta = ktime_sub(hrtimer_get_expires(&ts->sched_timer), now); |
Thomas Gleixner | c4bd822 | 2008-10-21 20:17:35 +0200 | [diff] [blame] | 682 | if (delta.tv64 <= tick_period.tv64) |
| 683 | return; |
| 684 | |
| 685 | tick_nohz_restart(ts, now); |
Thomas Gleixner | ae99286 | 2008-11-10 13:20:23 +0100 | [diff] [blame] | 686 | #endif |
Thomas Gleixner | fb02fbc | 2008-10-17 10:01:23 +0200 | [diff] [blame] | 687 | } |
| 688 | |
Martin Schwidefsky | eed3b9c | 2009-09-29 14:25:15 +0200 | [diff] [blame] | 689 | static inline void tick_check_nohz(int cpu) |
| 690 | { |
| 691 | struct tick_sched *ts = &per_cpu(tick_cpu_sched, cpu); |
| 692 | ktime_t now; |
| 693 | |
| 694 | if (!ts->idle_active && !ts->tick_stopped) |
| 695 | return; |
| 696 | now = ktime_get(); |
| 697 | if (ts->idle_active) |
| 698 | tick_nohz_stop_idle(cpu, now); |
| 699 | if (ts->tick_stopped) { |
| 700 | tick_nohz_update_jiffies(now); |
| 701 | tick_nohz_kick_tick(cpu, now); |
| 702 | } |
| 703 | } |
| 704 | |
Thomas Gleixner | 79bf2bb | 2007-02-16 01:28:03 -0800 | [diff] [blame] | 705 | #else |
| 706 | |
| 707 | static inline void tick_nohz_switch_to_nohz(void) { } |
Martin Schwidefsky | eed3b9c | 2009-09-29 14:25:15 +0200 | [diff] [blame] | 708 | static inline void tick_check_nohz(int cpu) { } |
Thomas Gleixner | 79bf2bb | 2007-02-16 01:28:03 -0800 | [diff] [blame] | 709 | |
| 710 | #endif /* NO_HZ */ |
| 711 | |
| 712 | /* |
Thomas Gleixner | 719254f | 2008-10-17 09:59:47 +0200 | [diff] [blame] | 713 | * Called from irq_enter to notify about the possible interruption of idle() |
| 714 | */ |
| 715 | void tick_check_idle(int cpu) |
| 716 | { |
Thomas Gleixner | fb02fbc | 2008-10-17 10:01:23 +0200 | [diff] [blame] | 717 | tick_check_oneshot_broadcast(cpu); |
Martin Schwidefsky | eed3b9c | 2009-09-29 14:25:15 +0200 | [diff] [blame] | 718 | tick_check_nohz(cpu); |
Thomas Gleixner | 719254f | 2008-10-17 09:59:47 +0200 | [diff] [blame] | 719 | } |
| 720 | |
| 721 | /* |
Thomas Gleixner | 79bf2bb | 2007-02-16 01:28:03 -0800 | [diff] [blame] | 722 | * High resolution timer specific code |
| 723 | */ |
| 724 | #ifdef CONFIG_HIGH_RES_TIMERS |
| 725 | /* |
Pavel Machek | 4c9dc64 | 2008-01-30 13:30:00 +0100 | [diff] [blame] | 726 | * We rearm the timer until we get disabled by the idle code. |
Thomas Gleixner | 79bf2bb | 2007-02-16 01:28:03 -0800 | [diff] [blame] | 727 | * Called with interrupts disabled and timer->base->cpu_base->lock held. |
| 728 | */ |
| 729 | static enum hrtimer_restart tick_sched_timer(struct hrtimer *timer) |
| 730 | { |
| 731 | struct tick_sched *ts = |
| 732 | container_of(timer, struct tick_sched, sched_timer); |
Thomas Gleixner | 79bf2bb | 2007-02-16 01:28:03 -0800 | [diff] [blame] | 733 | struct pt_regs *regs = get_irq_regs(); |
| 734 | ktime_t now = ktime_get(); |
Thomas Gleixner | d3ed782 | 2007-05-08 00:30:03 -0700 | [diff] [blame] | 735 | int cpu = smp_processor_id(); |
| 736 | |
| 737 | #ifdef CONFIG_NO_HZ |
| 738 | /* |
| 739 | * Check if the do_timer duty was dropped. We don't care about |
| 740 | * concurrency: This happens only when the cpu in charge went |
| 741 | * into a long sleep. If two cpus happen to assign themself to |
| 742 | * this duty, then the jiffies update is still serialized by |
| 743 | * xtime_lock. |
| 744 | */ |
Thomas Gleixner | 6441402 | 2008-09-22 18:46:37 +0200 | [diff] [blame] | 745 | if (unlikely(tick_do_timer_cpu == TICK_DO_TIMER_NONE)) |
Thomas Gleixner | d3ed782 | 2007-05-08 00:30:03 -0700 | [diff] [blame] | 746 | tick_do_timer_cpu = cpu; |
| 747 | #endif |
Thomas Gleixner | 79bf2bb | 2007-02-16 01:28:03 -0800 | [diff] [blame] | 748 | |
| 749 | /* Check, if the jiffies need an update */ |
Thomas Gleixner | d3ed782 | 2007-05-08 00:30:03 -0700 | [diff] [blame] | 750 | if (tick_do_timer_cpu == cpu) |
| 751 | tick_do_update_jiffies64(now); |
Thomas Gleixner | 79bf2bb | 2007-02-16 01:28:03 -0800 | [diff] [blame] | 752 | |
| 753 | /* |
| 754 | * Do not call, when we are not in irq context and have |
| 755 | * no valid regs pointer |
| 756 | */ |
| 757 | if (regs) { |
| 758 | /* |
| 759 | * When we are idle and the tick is stopped, we have to touch |
| 760 | * the watchdog as we might not schedule for a really long |
| 761 | * time. This happens on complete idle SMP systems while |
| 762 | * waiting on the login prompt. We also increment the "start of |
| 763 | * idle" jiffy stamp so the idle accounting adjustment we do |
| 764 | * when we go busy again does not account too much ticks. |
| 765 | */ |
| 766 | if (ts->tick_stopped) { |
| 767 | touch_softlockup_watchdog(); |
| 768 | ts->idle_jiffies++; |
| 769 | } |
Thomas Gleixner | 79bf2bb | 2007-02-16 01:28:03 -0800 | [diff] [blame] | 770 | update_process_times(user_mode(regs)); |
| 771 | profile_tick(CPU_PROFILING); |
Thomas Gleixner | 79bf2bb | 2007-02-16 01:28:03 -0800 | [diff] [blame] | 772 | } |
| 773 | |
Thomas Gleixner | 79bf2bb | 2007-02-16 01:28:03 -0800 | [diff] [blame] | 774 | hrtimer_forward(timer, now, tick_period); |
| 775 | |
| 776 | return HRTIMER_RESTART; |
| 777 | } |
| 778 | |
| 779 | /** |
| 780 | * tick_setup_sched_timer - setup the tick emulation timer |
| 781 | */ |
| 782 | void tick_setup_sched_timer(void) |
| 783 | { |
| 784 | struct tick_sched *ts = &__get_cpu_var(tick_cpu_sched); |
| 785 | ktime_t now = ktime_get(); |
john stultz | 3704540 | 2007-07-21 04:37:35 -0700 | [diff] [blame] | 786 | u64 offset; |
Thomas Gleixner | 79bf2bb | 2007-02-16 01:28:03 -0800 | [diff] [blame] | 787 | |
| 788 | /* |
| 789 | * Emulate tick processing via per-CPU hrtimers: |
| 790 | */ |
| 791 | hrtimer_init(&ts->sched_timer, CLOCK_MONOTONIC, HRTIMER_MODE_ABS); |
| 792 | ts->sched_timer.function = tick_sched_timer; |
Thomas Gleixner | 79bf2bb | 2007-02-16 01:28:03 -0800 | [diff] [blame] | 793 | |
john stultz | 3704540 | 2007-07-21 04:37:35 -0700 | [diff] [blame] | 794 | /* Get the next period (per cpu) */ |
Arjan van de Ven | cc584b2 | 2008-09-01 15:02:30 -0700 | [diff] [blame] | 795 | hrtimer_set_expires(&ts->sched_timer, tick_init_jiffy_update()); |
john stultz | 3704540 | 2007-07-21 04:37:35 -0700 | [diff] [blame] | 796 | offset = ktime_to_ns(tick_period) >> 1; |
john stultz | b2d9323 | 2007-10-16 23:27:18 -0700 | [diff] [blame] | 797 | do_div(offset, num_possible_cpus()); |
john stultz | 3704540 | 2007-07-21 04:37:35 -0700 | [diff] [blame] | 798 | offset *= smp_processor_id(); |
Arjan van de Ven | cc584b2 | 2008-09-01 15:02:30 -0700 | [diff] [blame] | 799 | hrtimer_add_expires_ns(&ts->sched_timer, offset); |
Thomas Gleixner | 79bf2bb | 2007-02-16 01:28:03 -0800 | [diff] [blame] | 800 | |
| 801 | for (;;) { |
| 802 | hrtimer_forward(&ts->sched_timer, now, tick_period); |
Arun R Bharadwaj | 5c33386 | 2009-04-16 12:14:37 +0530 | [diff] [blame] | 803 | hrtimer_start_expires(&ts->sched_timer, |
| 804 | HRTIMER_MODE_ABS_PINNED); |
Thomas Gleixner | 79bf2bb | 2007-02-16 01:28:03 -0800 | [diff] [blame] | 805 | /* Check, if the timer was already in the past */ |
| 806 | if (hrtimer_active(&ts->sched_timer)) |
| 807 | break; |
| 808 | now = ktime_get(); |
| 809 | } |
| 810 | |
| 811 | #ifdef CONFIG_NO_HZ |
| 812 | if (tick_nohz_enabled) |
| 813 | ts->nohz_mode = NOHZ_MODE_HIGHRES; |
| 814 | #endif |
| 815 | } |
Miao Xie | 3c4fbe5 | 2008-08-20 16:37:38 -0700 | [diff] [blame] | 816 | #endif /* HIGH_RES_TIMERS */ |
Thomas Gleixner | 79bf2bb | 2007-02-16 01:28:03 -0800 | [diff] [blame] | 817 | |
Miao Xie | 3c4fbe5 | 2008-08-20 16:37:38 -0700 | [diff] [blame] | 818 | #if defined CONFIG_NO_HZ || defined CONFIG_HIGH_RES_TIMERS |
Thomas Gleixner | 79bf2bb | 2007-02-16 01:28:03 -0800 | [diff] [blame] | 819 | void tick_cancel_sched_timer(int cpu) |
| 820 | { |
| 821 | struct tick_sched *ts = &per_cpu(tick_cpu_sched, cpu); |
| 822 | |
Miao Xie | 3c4fbe5 | 2008-08-20 16:37:38 -0700 | [diff] [blame] | 823 | # ifdef CONFIG_HIGH_RES_TIMERS |
Thomas Gleixner | 79bf2bb | 2007-02-16 01:28:03 -0800 | [diff] [blame] | 824 | if (ts->sched_timer.base) |
| 825 | hrtimer_cancel(&ts->sched_timer); |
Miao Xie | 3c4fbe5 | 2008-08-20 16:37:38 -0700 | [diff] [blame] | 826 | # endif |
Karsten Wiese | a790176 | 2008-03-04 14:59:55 -0800 | [diff] [blame] | 827 | |
Thomas Gleixner | 79bf2bb | 2007-02-16 01:28:03 -0800 | [diff] [blame] | 828 | ts->nohz_mode = NOHZ_MODE_INACTIVE; |
| 829 | } |
Miao Xie | 3c4fbe5 | 2008-08-20 16:37:38 -0700 | [diff] [blame] | 830 | #endif |
Thomas Gleixner | 79bf2bb | 2007-02-16 01:28:03 -0800 | [diff] [blame] | 831 | |
| 832 | /** |
| 833 | * Async notification about clocksource changes |
| 834 | */ |
| 835 | void tick_clock_notify(void) |
| 836 | { |
| 837 | int cpu; |
| 838 | |
| 839 | for_each_possible_cpu(cpu) |
| 840 | set_bit(0, &per_cpu(tick_cpu_sched, cpu).check_clocks); |
| 841 | } |
| 842 | |
| 843 | /* |
| 844 | * Async notification about clock event changes |
| 845 | */ |
| 846 | void tick_oneshot_notify(void) |
| 847 | { |
| 848 | struct tick_sched *ts = &__get_cpu_var(tick_cpu_sched); |
| 849 | |
| 850 | set_bit(0, &ts->check_clocks); |
| 851 | } |
| 852 | |
| 853 | /** |
| 854 | * Check, if a change happened, which makes oneshot possible. |
| 855 | * |
| 856 | * Called cyclic from the hrtimer softirq (driven by the timer |
| 857 | * softirq) allow_nohz signals, that we can switch into low-res nohz |
| 858 | * mode, because high resolution timers are disabled (either compile |
| 859 | * or runtime). |
| 860 | */ |
| 861 | int tick_check_oneshot_change(int allow_nohz) |
| 862 | { |
| 863 | struct tick_sched *ts = &__get_cpu_var(tick_cpu_sched); |
| 864 | |
| 865 | if (!test_and_clear_bit(0, &ts->check_clocks)) |
| 866 | return 0; |
| 867 | |
| 868 | if (ts->nohz_mode != NOHZ_MODE_INACTIVE) |
| 869 | return 0; |
| 870 | |
Li Zefan | cf4fc6c | 2008-02-08 04:19:24 -0800 | [diff] [blame] | 871 | if (!timekeeping_valid_for_hres() || !tick_is_oneshot_available()) |
Thomas Gleixner | 79bf2bb | 2007-02-16 01:28:03 -0800 | [diff] [blame] | 872 | return 0; |
| 873 | |
| 874 | if (!allow_nohz) |
| 875 | return 1; |
| 876 | |
| 877 | tick_nohz_switch_to_nohz(); |
| 878 | return 0; |
| 879 | } |