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/* -----------------------------------------------------------------------------
*
* (c) The GHC Team, 1995-2007
*
* Interval timer for profiling and pre-emptive scheduling.
*
* ---------------------------------------------------------------------------*/
/*
* We use a realtime timer by default. I found this much more
* reliable than a CPU timer:
*
* Experiments with different frequences: using
* CLOCK_REALTIME/CLOCK_MONOTONIC on Linux 2.6.32,
* 1000us has <1% impact on runtime
* 100us has ~2% impact on runtime
* 10us has ~40% impact on runtime
*
* using CLOCK_PROCESS_CPUTIME_ID on Linux 2.6.32,
* I cannot get it to tick faster than 10ms (10000us)
* which isn't great for profiling.
*
* In the threaded RTS, we can't tick in CPU time because the thread
* which has the virtual timer might be idle, so the tick would never
* fire. Therfore we used to tick in realtime in the threaded RTS and
* in CPU time otherwise, but now we always tick in realtime, for
* several reasons:
*
* - resolution (see above)
* - consistency (-threaded is the same as normal)
* - more consistency: Windows only has a realtime timer
*
* Note we want to use CLOCK_MONOTONIC rather than CLOCK_REALTIME,
* because the latter may jump around (NTP adjustments, leap seconds
* etc.).
*/
#include "PosixSource.h"
#include "Rts.h"
#include "Ticker.h"
#include "Proftimer.h"
#include "Schedule.h"
#include "posix/Clock.h"
/* As recommended in the autoconf manual */
# ifdef TIME_WITH_SYS_TIME
# include <sys/time.h>
# include <time.h>
# else
# ifdef HAVE_SYS_TIME_H
# include <sys/time.h>
# else
# include <time.h>
# endif
# endif
#ifdef HAVE_SIGNAL_H
# include <signal.h>
#endif
#include <string.h>
#include <pthread.h>
#include <unistd.h>
#include <fcntl.h>
#if HAVE_SYS_TIMERFD_H
#include <sys/timerfd.h>
#define USE_TIMERFD_FOR_ITIMER 1
#else
#define USE_TIMERFD_FOR_ITIMER 0
#endif
/*
* TFD_CLOEXEC has been added in Linux 2.6.26.
* If it is not available, we use fcntl(F_SETFD).
*/
#ifndef TFD_CLOEXEC
#define TFD_CLOEXEC 0
#endif
static Time itimer_interval = DEFAULT_TICK_INTERVAL;
enum ItimerState {STOPPED, RUNNING, STOPPING, EXITED};
static volatile enum ItimerState itimer_state = STOPPED;
static void *itimer_thread_func(void *_handle_tick)
{
TickProc handle_tick = _handle_tick;
uint64_t nticks;
int timerfd = -1;
#if USE_TIMERFD_FOR_ITIMER
struct itimerspec it;
it.it_value.tv_sec = TimeToSeconds(itimer_interval);
it.it_value.tv_nsec = TimeToNS(itimer_interval) % 1000000000;
it.it_interval = it.it_value;
timerfd = timerfd_create(CLOCK_MONOTONIC, TFD_CLOEXEC);
if (timerfd == -1) {
sysErrorBelch("timerfd_create");
stg_exit(EXIT_FAILURE);
}
if (!TFD_CLOEXEC) {
fcntl(timerfd, F_SETFD, FD_CLOEXEC);
}
if (timerfd_settime(timerfd, 0, &it, NULL)) {
sysErrorBelch("timerfd_settime");
stg_exit(EXIT_FAILURE);
}
#endif
while (1) {
if (USE_TIMERFD_FOR_ITIMER) {
if (read(timerfd, &nticks, sizeof(nticks)) != sizeof(nticks)) {
if (errno != EINTR) {
sysErrorBelch("Itimer: read(timerfd) failed");
}
}
} else {
if (usleep(TimeToUS(itimer_interval)) != 0 && errno != EINTR) {
sysErrorBelch("usleep(TimeToUS(itimer_interval) failed");
}
}
switch (itimer_state) {
case RUNNING:
handle_tick(0);
break;
case STOPPED:
break;
case STOPPING:
itimer_state = STOPPED;
break;
case EXITED:
if (USE_TIMERFD_FOR_ITIMER)
close(timerfd);
return NULL;
}
}
return NULL; // Never reached.
}
void
initTicker (Time interval, TickProc handle_tick)
{
itimer_interval = interval;
pthread_t tid;
int r = pthread_create(&tid, NULL, itimer_thread_func, (void*)handle_tick);
if (!r) {
pthread_detach(tid);
#if HAVE_PTHREAD_SETNAME_NP
pthread_setname_np(tid, "ghc_ticker");
#endif
}
}
void
startTicker(void)
{
// sanity check
if (itimer_state == EXITED) {
sysErrorBelch("ITimer: Tried to start a dead timer!\n");
stg_exit(EXIT_FAILURE);
}
itimer_state = RUNNING;
}
void
stopTicker(void)
{
if (itimer_state == RUNNING) {
itimer_state = STOPPING;
// Note that the timer may fire once more, but that's okay;
// handle_tick is only called when itimer_state == RUNNING
}
}
void
exitTicker (rtsBool wait STG_UNUSED)
{
itimer_state = EXITED;
}
int
rtsTimerSignal(void)
{
return SIGALRM;
}
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