2 * Copyright (c) 2008, 2009, 2010, 2011 Nicira Networks.
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at:
8 * http://www.apache.org/licenses/LICENSE-2.0
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
26 #include <sys/resource.h>
30 #include "fatal-signal.h"
36 VLOG_DEFINE_THIS_MODULE(timeval);
38 /* The clock to use for measuring time intervals. This is CLOCK_MONOTONIC by
39 * preference, but on systems that don't have a monotonic clock we fall back
40 * to CLOCK_REALTIME. */
41 static clockid_t monotonic_clock;
43 /* Has a timer tick occurred?
45 * We initialize these to true to force time_init() to get called on the first
46 * call to time_msec() or another function that queries the current time. */
47 static volatile sig_atomic_t wall_tick = true;
48 static volatile sig_atomic_t monotonic_tick = true;
50 /* The current time, as of the last refresh. */
51 static struct timespec wall_time;
52 static struct timespec monotonic_time;
54 /* Fixed monotonic time offset, for use by unit tests. */
55 static struct timespec warp_offset;
57 /* Time at which to die with SIGALRM (if not TIME_MIN). */
58 static time_t deadline = TIME_MIN;
60 static void set_up_timer(void);
61 static void set_up_signal(int flags);
62 static void sigalrm_handler(int);
63 static void refresh_wall_if_ticked(void);
64 static void refresh_monotonic_if_ticked(void);
65 static time_t time_add(time_t, time_t);
66 static void block_sigalrm(sigset_t *);
67 static void unblock_sigalrm(const sigset_t *);
68 static void log_poll_interval(long long int last_wakeup);
69 static struct rusage *get_recent_rusage(void);
70 static void refresh_rusage(void);
71 static void timespec_add(struct timespec *sum,
72 const struct timespec *a, const struct timespec *b);
74 /* Initializes the timetracking module.
76 * It is not necessary to call this function directly, because other time
77 * functions will call it automatically, but it doesn't hurt. */
89 if (!clock_gettime(CLOCK_MONOTONIC, &monotonic_time)) {
90 monotonic_clock = CLOCK_MONOTONIC;
92 monotonic_clock = CLOCK_REALTIME;
93 VLOG_DBG("monotonic timer not available");
96 set_up_signal(SA_RESTART);
101 set_up_signal(int flags)
105 memset(&sa, 0, sizeof sa);
106 sa.sa_handler = sigalrm_handler;
107 sigemptyset(&sa.sa_mask);
109 xsigaction(SIGALRM, &sa, NULL);
112 /* Remove SA_RESTART from the flags for SIGALRM, so that any system call that
113 * is interrupted by the periodic timer interrupt will return EINTR instead of
114 * continuing after the signal handler returns.
116 * time_disable_restart() and time_enable_restart() may be usefully wrapped
117 * around function calls that might otherwise block forever unless interrupted
120 * time_disable_restart();
121 * fcntl(fd, F_SETLKW, &lock);
122 * time_enable_restart();
125 time_disable_restart(void)
131 /* Add SA_RESTART to the flags for SIGALRM, so that any system call that
132 * is interrupted by the periodic timer interrupt will continue after the
133 * signal handler returns instead of returning EINTR. */
135 time_enable_restart(void)
138 set_up_signal(SA_RESTART);
144 static timer_t timer_id; /* "static" to avoid apparent memory leak. */
145 struct itimerspec itimer;
147 if (timer_create(monotonic_clock, NULL, &timer_id)) {
148 VLOG_FATAL("timer_create failed (%s)", strerror(errno));
151 itimer.it_interval.tv_sec = 0;
152 itimer.it_interval.tv_nsec = TIME_UPDATE_INTERVAL * 1000 * 1000;
153 itimer.it_value = itimer.it_interval;
155 if (timer_settime(timer_id, 0, &itimer, NULL)) {
156 VLOG_FATAL("timer_settime failed (%s)", strerror(errno));
160 /* Set up the interval timer, to ensure that time advances even without calling
163 * A child created with fork() does not inherit the parent's interval timer, so
164 * this function needs to be called from the child after fork(). */
176 clock_gettime(CLOCK_REALTIME, &wall_time);
181 refresh_monotonic(void)
185 if (monotonic_clock == CLOCK_MONOTONIC) {
186 clock_gettime(monotonic_clock, &monotonic_time);
188 refresh_wall_if_ticked();
189 monotonic_time = wall_time;
191 timespec_add(&monotonic_time, &monotonic_time, &warp_offset);
193 monotonic_tick = false;
196 /* Forces a refresh of the current time from the kernel. It is not usually
197 * necessary to call this function, since the time will be refreshed
198 * automatically at least every TIME_UPDATE_INTERVAL milliseconds. */
202 wall_tick = monotonic_tick = true;
205 /* Returns a monotonic timer, in seconds. */
209 refresh_monotonic_if_ticked();
210 return monotonic_time.tv_sec;
213 /* Same as time_now() except does not write to static variables, for use in
214 * signal handlers. */
218 struct timespec cur_time;
220 clock_gettime(monotonic_clock, &cur_time);
221 return cur_time.tv_sec;
224 /* Returns the current time, in seconds. */
228 refresh_wall_if_ticked();
229 return wall_time.tv_sec;
232 /* Returns a monotonic timer, in ms (within TIME_UPDATE_INTERVAL ms). */
236 refresh_monotonic_if_ticked();
237 return timespec_to_msec(&monotonic_time);
240 /* Returns the current time, in ms (within TIME_UPDATE_INTERVAL ms). */
244 refresh_wall_if_ticked();
245 return timespec_to_msec(&wall_time);
248 /* Stores a monotonic timer, accurate within TIME_UPDATE_INTERVAL ms, into
251 time_timespec(struct timespec *ts)
253 refresh_monotonic_if_ticked();
254 *ts = monotonic_time;
257 /* Stores the current time, accurate within TIME_UPDATE_INTERVAL ms, into
260 time_wall_timespec(struct timespec *ts)
262 refresh_wall_if_ticked();
266 /* Configures the program to die with SIGALRM 'secs' seconds from now, if
267 * 'secs' is nonzero, or disables the feature if 'secs' is zero. */
269 time_alarm(unsigned int secs)
274 block_sigalrm(&oldsigs);
275 deadline = secs ? time_add(time_now(), secs) : TIME_MIN;
276 unblock_sigalrm(&oldsigs);
279 /* Like poll(), except:
281 * - The timeout is specified as an absolute time, as defined by
282 * time_msec(), instead of a duration.
284 * - On error, returns a negative error code (instead of setting errno).
286 * - If interrupted by a signal, retries automatically until the original
287 * timeout is reached. (Because of this property, this function will
288 * never return -EINTR.)
290 * - As a side effect, refreshes the current time (like time_refresh()).
292 * Stores the number of milliseconds elapsed during poll in '*elapsed'. */
294 time_poll(struct pollfd *pollfds, int n_pollfds, long long int timeout_when,
297 static long long int last_wakeup;
304 log_poll_interval(last_wakeup);
309 long long int now = time_msec();
312 if (now >= timeout_when) {
314 } else if ((unsigned long long int) timeout_when - now > INT_MAX) {
317 time_left = timeout_when - now;
320 retval = poll(pollfds, n_pollfds, time_left);
325 if (retval != -EINTR) {
329 if (!blocked && deadline == TIME_MIN) {
330 block_sigalrm(&oldsigs);
335 unblock_sigalrm(&oldsigs);
337 last_wakeup = time_msec();
339 *elapsed = last_wakeup - start;
343 /* Returns the sum of 'a' and 'b', with saturation on overflow or underflow. */
345 time_add(time_t a, time_t b)
348 ? (b > TIME_MAX - a ? TIME_MAX : a + b)
349 : (b < TIME_MIN - a ? TIME_MIN : a + b));
353 sigalrm_handler(int sig_nr)
356 monotonic_tick = true;
357 if (deadline != TIME_MIN && time_now_sig() > deadline) {
358 fatal_signal_handler(sig_nr);
363 refresh_wall_if_ticked(void)
371 refresh_monotonic_if_ticked(void)
373 if (monotonic_tick) {
379 block_sigalrm(sigset_t *oldsigs)
382 sigemptyset(&sigalrm);
383 sigaddset(&sigalrm, SIGALRM);
384 xsigprocmask(SIG_BLOCK, &sigalrm, oldsigs);
388 unblock_sigalrm(const sigset_t *oldsigs)
390 xsigprocmask(SIG_SETMASK, oldsigs, NULL);
394 timespec_to_msec(const struct timespec *ts)
396 return (long long int) ts->tv_sec * 1000 + ts->tv_nsec / (1000 * 1000);
400 timeval_to_msec(const struct timeval *tv)
402 return (long long int) tv->tv_sec * 1000 + tv->tv_usec / 1000;
406 xgettimeofday(struct timeval *tv)
408 if (gettimeofday(tv, NULL) == -1) {
409 VLOG_FATAL("gettimeofday failed (%s)", strerror(errno));
414 timeval_diff_msec(const struct timeval *a, const struct timeval *b)
416 return timeval_to_msec(a) - timeval_to_msec(b);
420 timespec_add(struct timespec *sum,
421 const struct timespec *a,
422 const struct timespec *b)
426 tmp.tv_sec = a->tv_sec + b->tv_sec;
427 tmp.tv_nsec = a->tv_nsec + b->tv_nsec;
428 if (tmp.tv_nsec >= 1000 * 1000 * 1000) {
429 tmp.tv_nsec -= 1000 * 1000 * 1000;
437 log_poll_interval(long long int last_wakeup)
439 static unsigned int mean_interval; /* In 16ths of a millisecond. */
440 static unsigned int n_samples;
443 unsigned int interval; /* In 16ths of a millisecond. */
445 /* Compute interval from last wakeup to now in 16ths of a millisecond,
446 * capped at 10 seconds (16000 in this unit). */
448 interval = MIN(10000, now - last_wakeup) << 4;
450 /* Warn if we took too much time between polls: at least 50 ms and at least
451 * 8X the mean interval. */
452 if (n_samples > 10 && interval > mean_interval * 8 && interval > 50 * 16) {
453 const struct rusage *last_rusage = get_recent_rusage();
454 struct rusage rusage;
456 getrusage(RUSAGE_SELF, &rusage);
457 VLOG_WARN("%lld ms poll interval (%lld ms user, %lld ms system) "
458 "is over %u times the weighted mean interval %u ms "
461 timeval_diff_msec(&rusage.ru_utime, &last_rusage->ru_utime),
462 timeval_diff_msec(&rusage.ru_stime, &last_rusage->ru_stime),
463 interval / mean_interval,
464 (mean_interval + 8) / 16, n_samples);
465 if (rusage.ru_minflt > last_rusage->ru_minflt
466 || rusage.ru_majflt > last_rusage->ru_majflt) {
467 VLOG_WARN("faults: %ld minor, %ld major",
468 rusage.ru_minflt - last_rusage->ru_minflt,
469 rusage.ru_majflt - last_rusage->ru_majflt);
471 if (rusage.ru_inblock > last_rusage->ru_inblock
472 || rusage.ru_oublock > last_rusage->ru_oublock) {
473 VLOG_WARN("disk: %ld reads, %ld writes",
474 rusage.ru_inblock - last_rusage->ru_inblock,
475 rusage.ru_oublock - last_rusage->ru_oublock);
477 if (rusage.ru_nvcsw > last_rusage->ru_nvcsw
478 || rusage.ru_nivcsw > last_rusage->ru_nivcsw) {
479 VLOG_WARN("context switches: %ld voluntary, %ld involuntary",
480 rusage.ru_nvcsw - last_rusage->ru_nvcsw,
481 rusage.ru_nivcsw - last_rusage->ru_nivcsw);
484 /* Care should be taken in the value chosen for logging. Depending
485 * on the configuration, syslog can write changes synchronously,
486 * which can cause the coverage messages to take longer to log
487 * than the processing delay that triggered it. */
488 coverage_log(VLL_INFO, true);
491 /* Update exponentially weighted moving average. With these parameters, a
492 * given value decays to 1% of its value in about 100 time steps. */
494 mean_interval = (mean_interval * 122 + interval * 6 + 64) / 128;
496 mean_interval = interval;
500 /* CPU usage tracking. */
503 long long int when; /* Time that this sample was taken. */
504 unsigned long long int cpu; /* Total user+system CPU usage when sampled. */
507 static struct rusage recent_rusage;
508 static struct cpu_usage older = { LLONG_MIN, 0 };
509 static struct cpu_usage newer = { LLONG_MIN, 0 };
510 static int cpu_usage = -1;
512 static struct rusage *
513 get_recent_rusage(void)
515 return &recent_rusage;
524 getrusage(RUSAGE_SELF, &recent_rusage);
526 if (now >= newer.when + 3 * 1000) {
529 newer.cpu = (timeval_to_msec(&recent_rusage.ru_utime) +
530 timeval_to_msec(&recent_rusage.ru_stime));
532 if (older.when != LLONG_MIN && newer.cpu > older.cpu) {
533 unsigned int dividend = newer.cpu - older.cpu;
534 unsigned int divisor = (newer.when - older.when) / 100;
535 cpu_usage = divisor > 0 ? dividend / divisor : -1;
542 /* Returns an estimate of this process's CPU usage, as a percentage, over the
543 * past few seconds of wall-clock time. Returns -1 if no estimate is available
544 * (which will happen if the process has not been running long enough to have
545 * an estimate, and can happen for other reasons as well). */
552 /* Unixctl interface. */
555 timeval_warp_cb(struct unixctl_conn *conn,
556 int argc OVS_UNUSED, const char *argv[], void *aux OVS_UNUSED)
561 msecs = atoi(argv[1]);
563 unixctl_command_reply(conn, 501, "invalid MSECS");
567 ts.tv_sec = msecs / 1000;
568 ts.tv_nsec = (msecs % 1000) * 1000 * 1000;
569 timespec_add(&warp_offset, &warp_offset, &ts);
570 unixctl_command_reply(conn, 200, "warped");
574 timeval_dummy_register(void)
576 unixctl_command_register("time/warp", "MSECS", 1, 1,
577 timeval_warp_cb, NULL);