lib/timeval.c

   1 /*
   2  * Copyright (c) 2008, 2009, 2010, 2011, 2012 Nicira, Inc.
   3  *
   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:
   7  *
   8  *     http://www.apache.org/licenses/LICENSE-2.0
   9  *
  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.
  15  */
  16
  17 #include <config.h>
  18 #include "timeval.h"
  19 #include <assert.h>
  20 #include <errno.h>
  21 #if HAVE_EXECINFO_H
  22 #include <execinfo.h>
  23 #endif
  24 #include <poll.h>
  25 #include <signal.h>
  26 #include <stdlib.h>
  27 #include <string.h>
  28 #include <sys/time.h>
  29 #include <sys/resource.h>
  30 #include <unistd.h>
  31 #include "coverage.h"
  32 #include "dummy.h"
  33 #include "dynamic-string.h"
  34 #include "fatal-signal.h"
  35 #include "signals.h"
  36 #include "unixctl.h"
  37 #include "util.h"
  38 #include "vlog.h"
  39
  40 #ifndef HAVE_EXECINFO_H
  41 #define HAVE_EXECINFO_H 0
  42 #endif
  43
  44 VLOG_DEFINE_THIS_MODULE(timeval);
  45
  46 /* The clock to use for measuring time intervals.  This is CLOCK_MONOTONIC by
  47  * preference, but on systems that don't have a monotonic clock we fall back
  48  * to CLOCK_REALTIME. */
  49 static clockid_t monotonic_clock;
  50
  51 /* Has a timer tick occurred? Only relevant if CACHE_TIME is true.
  52  *
  53  * We initialize these to true to force time_init() to get called on the first
  54  * call to time_msec() or another function that queries the current time. */
  55 static volatile sig_atomic_t wall_tick = true;
  56 static volatile sig_atomic_t monotonic_tick = true;
  57
  58 /* The current time, as of the last refresh. */
  59 static struct timespec wall_time;
  60 static struct timespec monotonic_time;
  61
  62 /* The monotonic time at which the time module was initialized. */
  63 static long long int boot_time;
  64
  65 /* features for use by unit tests. */
  66 static struct timespec warp_offset; /* Offset added to monotonic_time. */
  67 static bool time_stopped;           /* Disables real-time updates, if true. */
  68
  69 /* Time in milliseconds at which to die with SIGALRM (if not LLONG_MAX). */
  70 static long long int deadline = LLONG_MAX;
  71
  72 struct trace {
  73     void *backtrace[32]; /* Populated by backtrace(). */
  74     size_t n_frames;     /* Number of frames in 'backtrace'. */
  75 };
  76
  77 #define MAX_TRACES 50
  78 static struct unixctl_conn *backtrace_conn = NULL;
  79 static struct trace *traces = NULL;
  80 static size_t n_traces = 0;
  81
  82 static void set_up_timer(void);
  83 static void set_up_signal(int flags);
  84 static void sigalrm_handler(int);
  85 static void refresh_wall_if_ticked(void);
  86 static void refresh_monotonic_if_ticked(void);
  87 static void block_sigalrm(sigset_t *);
  88 static void unblock_sigalrm(const sigset_t *);
  89 static void log_poll_interval(long long int last_wakeup);
  90 static struct rusage *get_recent_rusage(void);
  91 static void refresh_rusage(void);
  92 static void timespec_add(struct timespec *sum,
  93                          const struct timespec *a, const struct timespec *b);
  94 static void trace_run(void);
  95 static unixctl_cb_func backtrace_cb;
  96
  97 /* Initializes the timetracking module, if not already initialized. */
  98 static void
  99 time_init(void)
 100 {
 101     static bool inited;
 102
 103     /* The best place to do this is probably a timeval_run() function.
 104      * However, none exists and this function is usually so fast that doing it
 105      * here seems fine for now. */
 106     trace_run();
 107
 108     if (inited) {
 109         return;
 110     }
 111     inited = true;
 112
 113     if (HAVE_EXECINFO_H && CACHE_TIME) {
 114         unixctl_command_register("backtrace", "", 0, 0, backtrace_cb, NULL);
 115     }
 116
 117     coverage_init();
 118
 119     if (!clock_gettime(CLOCK_MONOTONIC, &monotonic_time)) {
 120         monotonic_clock = CLOCK_MONOTONIC;
 121     } else {
 122         monotonic_clock = CLOCK_REALTIME;
 123         VLOG_DBG("monotonic timer not available");
 124     }
 125
 126     set_up_signal(SA_RESTART);
 127     set_up_timer();
 128
 129     boot_time = time_msec();
 130 }
 131
 132 static void
 133 set_up_signal(int flags)
 134 {
 135     struct sigaction sa;
 136
 137     memset(&sa, 0, sizeof sa);
 138     sa.sa_handler = sigalrm_handler;
 139     sigemptyset(&sa.sa_mask);
 140     sa.sa_flags = flags;
 141     xsigaction(SIGALRM, &sa, NULL);
 142 }
 143
 144 /* Remove SA_RESTART from the flags for SIGALRM, so that any system call that
 145  * is interrupted by the periodic timer interrupt will return EINTR instead of
 146  * continuing after the signal handler returns.
 147  *
 148  * time_disable_restart() and time_enable_restart() may be usefully wrapped
 149  * around function calls that might otherwise block forever unless interrupted
 150  * by a signal, e.g.:
 151  *
 152  *   time_disable_restart();
 153  *   fcntl(fd, F_SETLKW, &lock);
 154  *   time_enable_restart();
 155  */
 156 void
 157 time_disable_restart(void)
 158 {
 159     time_init();
 160     set_up_signal(0);
 161 }
 162
 163 /* Add SA_RESTART to the flags for SIGALRM, so that any system call that
 164  * is interrupted by the periodic timer interrupt will continue after the
 165  * signal handler returns instead of returning EINTR. */
 166 void
 167 time_enable_restart(void)
 168 {
 169     time_init();
 170     set_up_signal(SA_RESTART);
 171 }
 172
 173 static void
 174 set_up_timer(void)
 175 {
 176     static timer_t timer_id;    /* "static" to avoid apparent memory leak. */
 177     struct itimerspec itimer;
 178
 179     if (!CACHE_TIME) {
 180         return;
 181     }
 182
 183     if (timer_create(monotonic_clock, NULL, &timer_id)) {
 184         VLOG_FATAL("timer_create failed (%s)", strerror(errno));
 185     }
 186
 187     itimer.it_interval.tv_sec = 0;
 188     itimer.it_interval.tv_nsec = TIME_UPDATE_INTERVAL * 1000 * 1000;
 189     itimer.it_value = itimer.it_interval;
 190
 191     if (timer_settime(timer_id, 0, &itimer, NULL)) {
 192         VLOG_FATAL("timer_settime failed (%s)", strerror(errno));
 193     }
 194 }
 195
 196 /* Set up the interval timer, to ensure that time advances even without calling
 197  * time_refresh().
 198  *
 199  * A child created with fork() does not inherit the parent's interval timer, so
 200  * this function needs to be called from the child after fork(). */
 201 void
 202 time_postfork(void)
 203 {
 204     time_init();
 205     set_up_timer();
 206 }
 207
 208 static void
 209 refresh_wall(void)
 210 {
 211     time_init();
 212     clock_gettime(CLOCK_REALTIME, &wall_time);
 213     wall_tick = false;
 214 }
 215
 216 static void
 217 refresh_monotonic(void)
 218 {
 219     time_init();
 220
 221     if (!time_stopped) {
 222         if (monotonic_clock == CLOCK_MONOTONIC) {
 223             clock_gettime(monotonic_clock, &monotonic_time);
 224         } else {
 225             refresh_wall_if_ticked();
 226             monotonic_time = wall_time;
 227         }
 228         timespec_add(&monotonic_time, &monotonic_time, &warp_offset);
 229
 230         monotonic_tick = false;
 231     }
 232 }
 233
 234 /* Forces a refresh of the current time from the kernel.  It is not usually
 235  * necessary to call this function, since the time will be refreshed
 236  * automatically at least every TIME_UPDATE_INTERVAL milliseconds.  If
 237  * CACHE_TIME is false, we will always refresh the current time so this
 238  * function has no effect. */
 239 void
 240 time_refresh(void)
 241 {
 242     wall_tick = monotonic_tick = true;
 243 }
 244
 245 /* Returns a monotonic timer, in seconds. */
 246 time_t
 247 time_now(void)
 248 {
 249     refresh_monotonic_if_ticked();
 250     return monotonic_time.tv_sec;
 251 }
 252
 253 /* Returns the current time, in seconds. */
 254 time_t
 255 time_wall(void)
 256 {
 257     refresh_wall_if_ticked();
 258     return wall_time.tv_sec;
 259 }
 260
 261 /* Returns a monotonic timer, in ms (within TIME_UPDATE_INTERVAL ms). */
 262 long long int
 263 time_msec(void)
 264 {
 265     refresh_monotonic_if_ticked();
 266     return timespec_to_msec(&monotonic_time);
 267 }
 268
 269 /* Returns the current time, in ms (within TIME_UPDATE_INTERVAL ms). */
 270 long long int
 271 time_wall_msec(void)
 272 {
 273     refresh_wall_if_ticked();
 274     return timespec_to_msec(&wall_time);
 275 }
 276
 277 /* Stores a monotonic timer, accurate within TIME_UPDATE_INTERVAL ms, into
 278  * '*ts'. */
 279 void
 280 time_timespec(struct timespec *ts)
 281 {
 282     refresh_monotonic_if_ticked();
 283     *ts = monotonic_time;
 284 }
 285
 286 /* Stores the current time, accurate within TIME_UPDATE_INTERVAL ms, into
 287  * '*ts'. */
 288 void
 289 time_wall_timespec(struct timespec *ts)
 290 {
 291     refresh_wall_if_ticked();
 292     *ts = wall_time;
 293 }
 294
 295 /* Configures the program to die with SIGALRM 'secs' seconds from now, if
 296  * 'secs' is nonzero, or disables the feature if 'secs' is zero. */
 297 void
 298 time_alarm(unsigned int secs)
 299 {
 300     long long int now;
 301     long long int msecs;
 302
 303     sigset_t oldsigs;
 304
 305     time_init();
 306     time_refresh();
 307
 308     now = time_msec();
 309     msecs = secs * 1000;
 310
 311     block_sigalrm(&oldsigs);
 312     deadline = now < LLONG_MAX - msecs ? now + msecs : LLONG_MAX;
 313     unblock_sigalrm(&oldsigs);
 314 }
 315
 316 /* Like poll(), except:
 317  *
 318  *      - The timeout is specified as an absolute time, as defined by
 319  *        time_msec(), instead of a duration.
 320  *
 321  *      - On error, returns a negative error code (instead of setting errno).
 322  *
 323  *      - If interrupted by a signal, retries automatically until the original
 324  *        timeout is reached.  (Because of this property, this function will
 325  *        never return -EINTR.)
 326  *
 327  *      - As a side effect, refreshes the current time (like time_refresh()).
 328  *
 329  * Stores the number of milliseconds elapsed during poll in '*elapsed'. */
 330 int
 331 time_poll(struct pollfd *pollfds, int n_pollfds, long long int timeout_when,
 332           int *elapsed)
 333 {
 334     static long long int last_wakeup = 0;
 335     long long int start;
 336     sigset_t oldsigs;
 337     bool blocked;
 338     int retval;
 339
 340     time_refresh();
 341     if (last_wakeup) {
 342         log_poll_interval(last_wakeup);
 343     }
 344     coverage_clear();
 345     start = time_msec();
 346     blocked = false;
 347
 348     timeout_when = MIN(timeout_when, deadline);
 349
 350     for (;;) {
 351         long long int now = time_msec();
 352         int time_left;
 353
 354         if (now >= timeout_when) {
 355             time_left = 0;
 356         } else if ((unsigned long long int) timeout_when - now > INT_MAX) {
 357             time_left = INT_MAX;
 358         } else {
 359             time_left = timeout_when - now;
 360         }
 361
 362         retval = poll(pollfds, n_pollfds, time_left);
 363         if (retval < 0) {
 364             retval = -errno;
 365         }
 366
 367         time_refresh();
 368         if (deadline <= time_msec()) {
 369             fatal_signal_handler(SIGALRM);
 370             if (retval < 0) {
 371                 retval = 0;
 372             }
 373             break;
 374         }
 375
 376         if (retval != -EINTR) {
 377             break;
 378         }
 379
 380         if (!blocked && CACHE_TIME && !backtrace_conn) {
 381             block_sigalrm(&oldsigs);
 382             blocked = true;
 383         }
 384     }
 385     if (blocked) {
 386         unblock_sigalrm(&oldsigs);
 387     }
 388     last_wakeup = time_msec();
 389     refresh_rusage();
 390     *elapsed = last_wakeup - start;
 391     return retval;
 392 }
 393
 394 static void
 395 sigalrm_handler(int sig_nr OVS_UNUSED)
 396 {
 397     wall_tick = true;
 398     monotonic_tick = true;
 399
 400 #if HAVE_EXECINFO_H
 401     if (backtrace_conn && n_traces < MAX_TRACES) {
 402         struct trace *trace = &traces[n_traces++];
 403         trace->n_frames = backtrace(trace->backtrace,
 404                                     ARRAY_SIZE(trace->backtrace));
 405     }
 406 #endif
 407 }
 408
 409 static void
 410 refresh_wall_if_ticked(void)
 411 {
 412     if (!CACHE_TIME || wall_tick) {
 413         refresh_wall();
 414     }
 415 }
 416
 417 static void
 418 refresh_monotonic_if_ticked(void)
 419 {
 420     if (!CACHE_TIME || monotonic_tick) {
 421         refresh_monotonic();
 422     }
 423 }
 424
 425 static void
 426 block_sigalrm(sigset_t *oldsigs)
 427 {
 428     sigset_t sigalrm;
 429     sigemptyset(&sigalrm);
 430     sigaddset(&sigalrm, SIGALRM);
 431     xsigprocmask(SIG_BLOCK, &sigalrm, oldsigs);
 432 }
 433
 434 static void
 435 unblock_sigalrm(const sigset_t *oldsigs)
 436 {
 437     xsigprocmask(SIG_SETMASK, oldsigs, NULL);
 438 }
 439
 440 long long int
 441 timespec_to_msec(const struct timespec *ts)
 442 {
 443     return (long long int) ts->tv_sec * 1000 + ts->tv_nsec / (1000 * 1000);
 444 }
 445
 446 long long int
 447 timeval_to_msec(const struct timeval *tv)
 448 {
 449     return (long long int) tv->tv_sec * 1000 + tv->tv_usec / 1000;
 450 }
 451
 452 /* Returns the monotonic time at which the "time" module was initialized, in
 453  * milliseconds(). */
 454 long long int
 455 time_boot_msec(void)
 456 {
 457     time_init();
 458     return boot_time;
 459 }
 460
 461 void
 462 xgettimeofday(struct timeval *tv)
 463 {
 464     if (gettimeofday(tv, NULL) == -1) {
 465         VLOG_FATAL("gettimeofday failed (%s)", strerror(errno));
 466     }
 467 }
 468
 469 static long long int
 470 timeval_diff_msec(const struct timeval *a, const struct timeval *b)
 471 {
 472     return timeval_to_msec(a) - timeval_to_msec(b);
 473 }
 474
 475 static void
 476 timespec_add(struct timespec *sum,
 477              const struct timespec *a,
 478              const struct timespec *b)
 479 {
 480     struct timespec tmp;
 481
 482     tmp.tv_sec = a->tv_sec + b->tv_sec;
 483     tmp.tv_nsec = a->tv_nsec + b->tv_nsec;
 484     if (tmp.tv_nsec >= 1000 * 1000 * 1000) {
 485         tmp.tv_nsec -= 1000 * 1000 * 1000;
 486         tmp.tv_sec++;
 487     }
 488
 489     *sum = tmp;
 490 }
 491
 492 static void
 493 log_poll_interval(long long int last_wakeup)
 494 {
 495     long long int interval = time_msec() - last_wakeup;
 496
 497     if (interval >= 1000) {
 498         const struct rusage *last_rusage = get_recent_rusage();
 499         struct rusage rusage;
 500
 501         getrusage(RUSAGE_SELF, &rusage);
 502         VLOG_WARN("Unreasonably long %lldms poll interval"
 503                   " (%lldms user, %lldms system)",
 504                   interval,
 505                   timeval_diff_msec(&rusage.ru_utime,
 506                                     &last_rusage->ru_utime),
 507                   timeval_diff_msec(&rusage.ru_stime,
 508                                     &last_rusage->ru_stime));
 509         if (rusage.ru_minflt > last_rusage->ru_minflt
 510             || rusage.ru_majflt > last_rusage->ru_majflt) {
 511             VLOG_WARN("faults: %ld minor, %ld major",
 512                       rusage.ru_minflt - last_rusage->ru_minflt,
 513                       rusage.ru_majflt - last_rusage->ru_majflt);
 514         }
 515         if (rusage.ru_inblock > last_rusage->ru_inblock
 516             || rusage.ru_oublock > last_rusage->ru_oublock) {
 517             VLOG_WARN("disk: %ld reads, %ld writes",
 518                       rusage.ru_inblock - last_rusage->ru_inblock,
 519                       rusage.ru_oublock - last_rusage->ru_oublock);
 520         }
 521         if (rusage.ru_nvcsw > last_rusage->ru_nvcsw
 522             || rusage.ru_nivcsw > last_rusage->ru_nivcsw) {
 523             VLOG_WARN("context switches: %ld voluntary, %ld involuntary",
 524                       rusage.ru_nvcsw - last_rusage->ru_nvcsw,
 525                       rusage.ru_nivcsw - last_rusage->ru_nivcsw);
 526         }
 527         coverage_log();
 528     }
 529 }
 530 \f
 531 /* CPU usage tracking. */
 532
 533 struct cpu_usage {
 534     long long int when;         /* Time that this sample was taken. */
 535     unsigned long long int cpu; /* Total user+system CPU usage when sampled. */
 536 };
 537
 538 static struct rusage recent_rusage;
 539 static struct cpu_usage older = { LLONG_MIN, 0 };
 540 static struct cpu_usage newer = { LLONG_MIN, 0 };
 541 static int cpu_usage = -1;
 542
 543 static struct rusage *
 544 get_recent_rusage(void)
 545 {
 546     return &recent_rusage;
 547 }
 548
 549 static void
 550 refresh_rusage(void)
 551 {
 552     long long int now;
 553
 554     now = time_msec();
 555     getrusage(RUSAGE_SELF, &recent_rusage);
 556
 557     if (now >= newer.when + 3 * 1000) {
 558         older = newer;
 559         newer.when = now;
 560         newer.cpu = (timeval_to_msec(&recent_rusage.ru_utime) +
 561                      timeval_to_msec(&recent_rusage.ru_stime));
 562
 563         if (older.when != LLONG_MIN && newer.cpu > older.cpu) {
 564             unsigned int dividend = newer.cpu - older.cpu;
 565             unsigned int divisor = (newer.when - older.when) / 100;
 566             cpu_usage = divisor > 0 ? dividend / divisor : -1;
 567         } else {
 568             cpu_usage = -1;
 569         }
 570     }
 571 }
 572
 573 /* Returns an estimate of this process's CPU usage, as a percentage, over the
 574  * past few seconds of wall-clock time.  Returns -1 if no estimate is available
 575  * (which will happen if the process has not been running long enough to have
 576  * an estimate, and can happen for other reasons as well). */
 577 int
 578 get_cpu_usage(void)
 579 {
 580     return cpu_usage;
 581 }
 582
 583 static void
 584 trace_run(void)
 585 {
 586 #if HAVE_EXECINFO_H
 587     if (backtrace_conn && n_traces >= MAX_TRACES) {
 588         struct unixctl_conn *reply_conn = backtrace_conn;
 589         struct ds ds = DS_EMPTY_INITIALIZER;
 590         sigset_t oldsigs;
 591         size_t i;
 592
 593         block_sigalrm(&oldsigs);
 594
 595         for (i = 0; i < n_traces; i++) {
 596             struct trace *trace = &traces[i];
 597             char **frame_strs;
 598             size_t j;
 599
 600             frame_strs = backtrace_symbols(trace->backtrace, trace->n_frames);
 601
 602             ds_put_format(&ds, "Backtrace %zu\n", i + 1);
 603             for (j = 0; j < trace->n_frames; j++) {
 604                 ds_put_format(&ds, "%s\n", frame_strs[j]);
 605             }
 606             ds_put_cstr(&ds, "\n");
 607
 608             free(frame_strs);
 609         }
 610
 611         free(traces);
 612         traces = NULL;
 613         n_traces = 0;
 614         backtrace_conn = NULL;
 615
 616         unblock_sigalrm(&oldsigs);
 617
 618         unixctl_command_reply(reply_conn, ds_cstr(&ds));
 619         ds_destroy(&ds);
 620     }
 621 #endif
 622 }
 623 \f
 624 /* Unixctl interface. */
 625
 626 /* "time/stop" stops the monotonic time returned by e.g. time_msec() from
 627  * advancing, except due to later calls to "time/warp". */
 628 static void
 629 timeval_stop_cb(struct unixctl_conn *conn,
 630                  int argc OVS_UNUSED, const char *argv[] OVS_UNUSED,
 631                  void *aux OVS_UNUSED)
 632 {
 633     time_stopped = true;
 634     unixctl_command_reply(conn, NULL);
 635 }
 636
 637 /* "time/warp MSECS" advances the current monotonic time by the specified
 638  * number of milliseconds.  Unless "time/stop" has also been executed, the
 639  * monotonic clock continues to tick forward at the normal rate afterward.
 640  *
 641  * Does not affect wall clock readings. */
 642 static void
 643 timeval_warp_cb(struct unixctl_conn *conn,
 644                 int argc OVS_UNUSED, const char *argv[], void *aux OVS_UNUSED)
 645 {
 646     struct timespec ts;
 647     int msecs;
 648
 649     msecs = atoi(argv[1]);
 650     if (msecs <= 0) {
 651         unixctl_command_reply_error(conn, "invalid MSECS");
 652         return;
 653     }
 654
 655     ts.tv_sec = msecs / 1000;
 656     ts.tv_nsec = (msecs % 1000) * 1000 * 1000;
 657     timespec_add(&warp_offset, &warp_offset, &ts);
 658     timespec_add(&monotonic_time, &monotonic_time, &ts);
 659     unixctl_command_reply(conn, "warped");
 660 }
 661
 662 static void
 663 backtrace_cb(struct unixctl_conn *conn,
 664              int argc OVS_UNUSED, const char *argv[] OVS_UNUSED,
 665              void *aux OVS_UNUSED)
 666 {
 667     sigset_t oldsigs;
 668
 669     assert(HAVE_EXECINFO_H && CACHE_TIME);
 670
 671     if (backtrace_conn) {
 672         unixctl_command_reply_error(conn, "In Use");
 673         return;
 674     }
 675     assert(!traces);
 676
 677     block_sigalrm(&oldsigs);
 678     backtrace_conn = conn;
 679     traces = xmalloc(MAX_TRACES * sizeof *traces);
 680     n_traces = 0;
 681     unblock_sigalrm(&oldsigs);
 682 }
 683
 684 void
 685 timeval_dummy_register(void)
 686 {
 687     unixctl_command_register("time/stop", "", 0, 0, timeval_stop_cb, NULL);
 688     unixctl_command_register("time/warp", "MSECS", 1, 1,
 689                              timeval_warp_cb, NULL);
 690 }