/usr/src/openvswitch-1.4.0/lib/timeval.c is in openvswitch-datapath-dkms 1.4.0-1ubuntu1.
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* Copyright (c) 2008, 2009, 2010, 2011 Nicira Networks.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at:
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
#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 "signals.h"
#include "util.h"
#include "vlog.h"
VLOG_DEFINE_THIS_MODULE(timeval);
/* The clock to use for measuring time intervals. This is CLOCK_MONOTONIC by
* preference, but on systems that don't have a monotonic clock we fall back
* to CLOCK_REALTIME. */
static clockid_t monotonic_clock;
/* Has a timer tick occurred?
*
* We initialize these to true to force time_init() to get called on the first
* call to time_msec() or another function that queries the current time. */
static volatile sig_atomic_t wall_tick = true;
static volatile sig_atomic_t monotonic_tick = true;
/* The current time, as of the last refresh. */
static struct timespec wall_time;
static struct timespec monotonic_time;
/* Time at which to die with SIGALRM (if not TIME_MIN). */
static time_t deadline = TIME_MIN;
static void set_up_timer(void);
static void set_up_signal(int flags);
static void sigalrm_handler(int);
static void refresh_wall_if_ticked(void);
static void refresh_monotonic_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);
static struct rusage *get_recent_rusage(void);
static void refresh_rusage(void);
/* Initializes the timetracking module.
*
* It is not necessary to call this function directly, because other time
* functions will call it automatically, but it doesn't hurt. */
static void
time_init(void)
{
static bool inited;
if (inited) {
return;
}
inited = true;
coverage_init();
if (!clock_gettime(CLOCK_MONOTONIC, &monotonic_time)) {
monotonic_clock = CLOCK_MONOTONIC;
} else {
monotonic_clock = CLOCK_REALTIME;
VLOG_DBG("monotonic timer not available");
}
set_up_signal(SA_RESTART);
set_up_timer();
}
static void
set_up_signal(int flags)
{
struct sigaction sa;
memset(&sa, 0, sizeof sa);
sa.sa_handler = sigalrm_handler;
sigemptyset(&sa.sa_mask);
sa.sa_flags = flags;
xsigaction(SIGALRM, &sa, NULL);
}
/* Remove SA_RESTART from the flags for SIGALRM, so that any system call that
* is interrupted by the periodic timer interrupt will return EINTR instead of
* continuing after the signal handler returns.
*
* time_disable_restart() and time_enable_restart() may be usefully wrapped
* around function calls that might otherwise block forever unless interrupted
* by a signal, e.g.:
*
* time_disable_restart();
* fcntl(fd, F_SETLKW, &lock);
* time_enable_restart();
*/
void
time_disable_restart(void)
{
time_init();
set_up_signal(0);
}
/* Add SA_RESTART to the flags for SIGALRM, so that any system call that
* is interrupted by the periodic timer interrupt will continue after the
* signal handler returns instead of returning EINTR. */
void
time_enable_restart(void)
{
time_init();
set_up_signal(SA_RESTART);
}
static void
set_up_timer(void)
{
static timer_t timer_id; /* "static" to avoid apparent memory leak. */
struct itimerspec itimer;
if (timer_create(monotonic_clock, NULL, &timer_id)) {
VLOG_FATAL("timer_create failed (%s)", strerror(errno));
}
itimer.it_interval.tv_sec = 0;
itimer.it_interval.tv_nsec = TIME_UPDATE_INTERVAL * 1000 * 1000;
itimer.it_value = itimer.it_interval;
if (timer_settime(timer_id, 0, &itimer, NULL)) {
VLOG_FATAL("timer_settime failed (%s)", strerror(errno));
}
}
/* Set up the interval timer, to ensure that time advances even without calling
* time_refresh().
*
* A child created with fork() does not inherit the parent's interval timer, so
* this function needs to be called from the child after fork(). */
void
time_postfork(void)
{
time_init();
set_up_timer();
}
static void
refresh_wall(void)
{
time_init();
clock_gettime(CLOCK_REALTIME, &wall_time);
wall_tick = false;
}
static void
refresh_monotonic(void)
{
time_init();
if (monotonic_clock == CLOCK_MONOTONIC) {
clock_gettime(monotonic_clock, &monotonic_time);
} else {
refresh_wall_if_ticked();
monotonic_time = wall_time;
}
monotonic_tick = false;
}
/* 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)
{
wall_tick = monotonic_tick = true;
}
/* Returns a monotonic timer, in seconds. */
time_t
time_now(void)
{
refresh_monotonic_if_ticked();
return monotonic_time.tv_sec;
}
/* Same as time_now() except does not write to static variables, for use in
* signal handlers. */
static time_t
time_now_sig(void)
{
struct timespec cur_time;
clock_gettime(monotonic_clock, &cur_time);
return cur_time.tv_sec;
}
/* Returns the current time, in seconds. */
time_t
time_wall(void)
{
refresh_wall_if_ticked();
return wall_time.tv_sec;
}
/* Returns a monotonic timer, in ms (within TIME_UPDATE_INTERVAL ms). */
long long int
time_msec(void)
{
refresh_monotonic_if_ticked();
return timespec_to_msec(&monotonic_time);
}
/* Returns the current time, in ms (within TIME_UPDATE_INTERVAL ms). */
long long int
time_wall_msec(void)
{
refresh_wall_if_ticked();
return timespec_to_msec(&wall_time);
}
/* Stores a monotonic timer, accurate within TIME_UPDATE_INTERVAL ms, into
* '*ts'. */
void
time_timespec(struct timespec *ts)
{
refresh_monotonic_if_ticked();
*ts = monotonic_time;
}
/* Stores the current time, accurate within TIME_UPDATE_INTERVAL ms, into
* '*ts'. */
void
time_wall_timespec(struct timespec *ts)
{
refresh_wall_if_ticked();
*ts = wall_time;
}
/* 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;
long long int start;
sigset_t oldsigs;
bool blocked;
int retval;
time_refresh();
log_poll_interval(last_wakeup);
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();
refresh_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)
{
wall_tick = true;
monotonic_tick = true;
if (deadline != TIME_MIN && time_now_sig() > deadline) {
fatal_signal_handler(sig_nr);
}
}
static void
refresh_wall_if_ticked(void)
{
if (wall_tick) {
refresh_wall();
}
}
static void
refresh_monotonic_if_ticked(void)
{
if (monotonic_tick) {
refresh_monotonic();
}
}
static void
block_sigalrm(sigset_t *oldsigs)
{
sigset_t sigalrm;
sigemptyset(&sigalrm);
sigaddset(&sigalrm, SIGALRM);
xsigprocmask(SIG_BLOCK, &sigalrm, oldsigs);
}
static void
unblock_sigalrm(const sigset_t *oldsigs)
{
xsigprocmask(SIG_SETMASK, oldsigs, NULL);
}
long long int
timespec_to_msec(const struct timespec *ts)
{
return (long long int) ts->tv_sec * 1000 + ts->tv_nsec / (1000 * 1000);
}
long long int
timeval_to_msec(const struct timeval *tv)
{
return (long long int) tv->tv_sec * 1000 + tv->tv_usec / 1000;
}
void
xgettimeofday(struct timeval *tv)
{
if (gettimeofday(tv, NULL) == -1) {
VLOG_FATAL("gettimeofday failed (%s)", strerror(errno));
}
}
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)
{
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: at least 50 ms and at least
* 8X the mean interval. */
if (n_samples > 10 && interval > mean_interval * 8 && interval > 50 * 16) {
const struct rusage *last_rusage = get_recent_rusage();
struct rusage rusage;
getrusage(RUSAGE_SELF, &rusage);
VLOG_WARN("%lld ms poll interval (%lld ms user, %lld ms system) "
"is over %u times the weighted mean interval %u ms "
"(%u samples)",
now - last_wakeup,
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);
}
/* Care should be taken in the value chosen for logging. Depending
* on the configuration, syslog can write changes synchronously,
* which can cause the coverage messages to take longer to log
* than the processing delay that triggered it. */
coverage_log(VLL_INFO, true);
}
/* 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;
}
}
/* CPU usage tracking. */
struct cpu_usage {
long long int when; /* Time that this sample was taken. */
unsigned long long int cpu; /* Total user+system CPU usage when sampled. */
};
static struct rusage recent_rusage;
static struct cpu_usage older = { LLONG_MIN, 0 };
static struct cpu_usage newer = { LLONG_MIN, 0 };
static int cpu_usage = -1;
static struct rusage *
get_recent_rusage(void)
{
return &recent_rusage;
}
static void
refresh_rusage(void)
{
long long int now;
now = time_msec();
getrusage(RUSAGE_SELF, &recent_rusage);
if (now >= newer.when + 3 * 1000) {
older = newer;
newer.when = now;
newer.cpu = (timeval_to_msec(&recent_rusage.ru_utime) +
timeval_to_msec(&recent_rusage.ru_stime));
if (older.when != LLONG_MIN && newer.cpu > older.cpu) {
unsigned int dividend = newer.cpu - older.cpu;
unsigned int divisor = (newer.when - older.when) / 100;
cpu_usage = divisor > 0 ? dividend / divisor : -1;
} else {
cpu_usage = -1;
}
}
}
/* Returns an estimate of this process's CPU usage, as a percentage, over the
* past few seconds of wall-clock time. Returns -1 if no estimate is available
* (which will happen if the process has not been running long enough to have
* an estimate, and can happen for other reasons as well). */
int
get_cpu_usage(void)
{
return cpu_usage;
}
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