diff options
Diffstat (limited to 'lib/timeval.c')
| -rw-r--r-- | lib/timeval.c | 305 |
1 files changed, 305 insertions, 0 deletions
diff --git a/lib/timeval.c b/lib/timeval.c new file mode 100644 index 000000000..b76993f9b --- /dev/null +++ b/lib/timeval.c @@ -0,0 +1,305 @@ +/* + * Copyright (c) 2008, 2009 Nicira Networks. + * + * Permission to use, copy, modify, and/or distribute this software for any + * purpose with or without fee is hereby granted, provided that the above + * copyright notice and this permission notice appear in all copies. + * + * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES + * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF + * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR + * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES + * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN + * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF + * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. + */ + +#include <config.h> +#include "timeval.h" +#include <assert.h> +#include <errno.h> +#include <poll.h> +#include <signal.h> +#include <string.h> +#include <sys/time.h> +#include <sys/resource.h> +#include <unistd.h> +#include "coverage.h" +#include "fatal-signal.h" +#include "util.h" + +#include "vlog.h" +#define THIS_MODULE VLM_timeval + +/* Initialized? */ +static bool inited; + +/* Has a timer tick occurred? */ +static volatile sig_atomic_t tick; + +/* The current time, as of the last refresh. */ +static struct timeval now; + +/* Time at which to die with SIGALRM (if not TIME_MIN). */ +static time_t deadline = TIME_MIN; + +static void sigalrm_handler(int); +static void refresh_if_ticked(void); +static time_t time_add(time_t, time_t); +static void block_sigalrm(sigset_t *); +static void unblock_sigalrm(const sigset_t *); +static void log_poll_interval(long long int last_wakeup, + const struct rusage *last_rusage); +static long long int timeval_to_msec(const struct timeval *); + +/* Initializes the timetracking module. */ +void +time_init(void) +{ + struct sigaction sa; + struct itimerval itimer; + + if (inited) { + return; + } + + inited = true; + gettimeofday(&now, NULL); + tick = false; + + /* Set up signal handler. */ + memset(&sa, 0, sizeof sa); + sa.sa_handler = sigalrm_handler; + sigemptyset(&sa.sa_mask); + sa.sa_flags = SA_RESTART; + if (sigaction(SIGALRM, &sa, NULL)) { + ovs_fatal(errno, "sigaction(SIGALRM) failed"); + } + + /* Set up periodic timer. */ + itimer.it_interval.tv_sec = 0; + itimer.it_interval.tv_usec = TIME_UPDATE_INTERVAL * 1000; + itimer.it_value = itimer.it_interval; + if (setitimer(ITIMER_REAL, &itimer, NULL)) { + ovs_fatal(errno, "setitimer failed"); + } +} + +/* Forces a refresh of the current time from the kernel. It is not usually + * necessary to call this function, since the time will be refreshed + * automatically at least every TIME_UPDATE_INTERVAL milliseconds. */ +void +time_refresh(void) +{ + gettimeofday(&now, NULL); + tick = false; +} + +/* Returns the current time, in seconds. */ +time_t +time_now(void) +{ + refresh_if_ticked(); + return now.tv_sec; +} + +/* Returns the current time, in ms (within TIME_UPDATE_INTERVAL ms). */ +long long int +time_msec(void) +{ + refresh_if_ticked(); + return timeval_to_msec(&now); +} + +/* Stores the current time, accurate within TIME_UPDATE_INTERVAL ms, into + * '*tv'. */ +void +time_timeval(struct timeval *tv) +{ + refresh_if_ticked(); + *tv = now; +} + +/* Configures the program to die with SIGALRM 'secs' seconds from now, if + * 'secs' is nonzero, or disables the feature if 'secs' is zero. */ +void +time_alarm(unsigned int secs) +{ + sigset_t oldsigs; + + time_init(); + block_sigalrm(&oldsigs); + deadline = secs ? time_add(time_now(), secs) : TIME_MIN; + unblock_sigalrm(&oldsigs); +} + +/* Like poll(), except: + * + * - On error, returns a negative error code (instead of setting errno). + * + * - If interrupted by a signal, retries automatically until the original + * 'timeout' expires. (Because of this property, this function will + * never return -EINTR.) + * + * - As a side effect, refreshes the current time (like time_refresh()). + */ +int +time_poll(struct pollfd *pollfds, int n_pollfds, int timeout) +{ + static long long int last_wakeup; + static struct rusage last_rusage; + long long int start; + sigset_t oldsigs; + bool blocked; + int retval; + + time_refresh(); + log_poll_interval(last_wakeup, &last_rusage); + coverage_clear(); + start = time_msec(); + blocked = false; + for (;;) { + int time_left; + if (timeout > 0) { + long long int elapsed = time_msec() - start; + time_left = timeout >= elapsed ? timeout - elapsed : 0; + } else { + time_left = timeout; + } + + retval = poll(pollfds, n_pollfds, time_left); + if (retval < 0) { + retval = -errno; + } + time_refresh(); + if (retval != -EINTR) { + break; + } + + if (!blocked && deadline == TIME_MIN) { + block_sigalrm(&oldsigs); + blocked = true; + } + } + if (blocked) { + unblock_sigalrm(&oldsigs); + } + last_wakeup = time_msec(); + getrusage(RUSAGE_SELF, &last_rusage); + return retval; +} + +/* Returns the sum of 'a' and 'b', with saturation on overflow or underflow. */ +static time_t +time_add(time_t a, time_t b) +{ + return (a >= 0 + ? (b > TIME_MAX - a ? TIME_MAX : a + b) + : (b < TIME_MIN - a ? TIME_MIN : a + b)); +} + +static void +sigalrm_handler(int sig_nr) +{ + tick = true; + if (deadline != TIME_MIN && time(0) > deadline) { + fatal_signal_handler(sig_nr); + } +} + +static void +refresh_if_ticked(void) +{ + assert(inited); + if (tick) { + time_refresh(); + } +} + +static void +block_sigalrm(sigset_t *oldsigs) +{ + sigset_t sigalrm; + sigemptyset(&sigalrm); + sigaddset(&sigalrm, SIGALRM); + if (sigprocmask(SIG_BLOCK, &sigalrm, oldsigs)) { + ovs_fatal(errno, "sigprocmask"); + } +} + +static void +unblock_sigalrm(const sigset_t *oldsigs) +{ + if (sigprocmask(SIG_SETMASK, oldsigs, NULL)) { + ovs_fatal(errno, "sigprocmask"); + } +} + +static long long int +timeval_to_msec(const struct timeval *tv) +{ + return (long long int) tv->tv_sec * 1000 + tv->tv_usec / 1000; +} + +static long long int +timeval_diff_msec(const struct timeval *a, const struct timeval *b) +{ + return timeval_to_msec(a) - timeval_to_msec(b); +} + +static void +log_poll_interval(long long int last_wakeup, const struct rusage *last_rusage) +{ + static unsigned int mean_interval; /* In 16ths of a millisecond. */ + static unsigned int n_samples; + + long long int now; + unsigned int interval; /* In 16ths of a millisecond. */ + + /* Compute interval from last wakeup to now in 16ths of a millisecond, + * capped at 10 seconds (16000 in this unit). */ + now = time_msec(); + interval = MIN(10000, now - last_wakeup) << 4; + + /* Warn if we took too much time between polls. */ + if (n_samples > 10 && interval > mean_interval * 8) { + struct rusage rusage; + + getrusage(RUSAGE_SELF, &rusage); + VLOG_WARN("%u ms poll interval (%lld ms user, %lld ms system) " + "is over %u times the weighted mean interval %u ms " + "(%u samples)", + (interval + 8) / 16, + timeval_diff_msec(&rusage.ru_utime, &last_rusage->ru_utime), + timeval_diff_msec(&rusage.ru_stime, &last_rusage->ru_stime), + interval / mean_interval, + (mean_interval + 8) / 16, n_samples); + if (rusage.ru_minflt > last_rusage->ru_minflt + || rusage.ru_majflt > last_rusage->ru_majflt) { + VLOG_WARN("faults: %ld minor, %ld major", + rusage.ru_minflt - last_rusage->ru_minflt, + rusage.ru_majflt - last_rusage->ru_majflt); + } + if (rusage.ru_inblock > last_rusage->ru_inblock + || rusage.ru_oublock > last_rusage->ru_oublock) { + VLOG_WARN("disk: %ld reads, %ld writes", + rusage.ru_inblock - last_rusage->ru_inblock, + rusage.ru_oublock - last_rusage->ru_oublock); + } + if (rusage.ru_nvcsw > last_rusage->ru_nvcsw + || rusage.ru_nivcsw > last_rusage->ru_nivcsw) { + VLOG_WARN("context switches: %ld voluntary, %ld involuntary", + rusage.ru_nvcsw - last_rusage->ru_nvcsw, + rusage.ru_nivcsw - last_rusage->ru_nivcsw); + } + coverage_log(VLL_WARN); + } + + /* Update exponentially weighted moving average. With these parameters, a + * given value decays to 1% of its value in about 100 time steps. */ + if (n_samples++) { + mean_interval = (mean_interval * 122 + interval * 6 + 64) / 128; + } else { + mean_interval = interval; + } +} |