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Overview
Comment:NRT relevant only: provides self-calibrating mechanism for TclpUSleep (the actual time of usleep/nanosleep may be longer, due to system latencies and possible limitations in the timer resolution of the hardware); forces context switch or yield the processor if sleep time to small.
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SHA3-256: 9ce15c7f1acd585fd94ab1fac058c1e5d4502ec434d9e3c973e2d640629ebcbd
User & Date: sebres 2019-03-09 21:04:55
Context
2019-05-22
09:18
merge 8.5 Leaf check-in: ba97c71d8f user: sebres tags: sebres-8-5-event-perf-branch
2019-03-09
21:22
merge 8-5-event-perf-branch check-in: 697065a8e5 user: sebres tags: sebres-8-6-event-perf-branch
21:04
NRT relevant only: provides self-calibrating mechanism for TclpUSleep (the actual time of usleep/nan... check-in: 9ce15c7f1a user: sebres tags: sebres-8-5-event-perf-branch
20:07
non-native time scale fixed: do scale time only once (not in cycle, since all other times used in ca... check-in: f20b5264a3 user: sebres tags: sebres-8-5-event-perf-branch
Changes
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Changes to unix/tclUnixNotfy.c.

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 *
 * Note: Adjusting of this values may increase NRT-capability, but also may
 * 	 increase CPU load (resp. busy waits on brief intervals).
 */

#ifndef TCL_TMR_MIN_DELAY
#   define TCL_TMR_MIN_DELAY 100
#   define TCL_TMR_MIN_SLEEP 50

#   define TCL_TMR_OVERHEAD 50
#endif

/*
 *----------------------------------------------------------------------
 *
 * TclpUSleep --
................................................................................
 *
 * Side effects:
 *	Time passes.
 *
 *----------------------------------------------------------------------
 */





void
TclpUSleep(
    Tcl_WideInt usec)	/* Time to sleep. */
{
    Tcl_WideInt now, desired;


    if (usec < 0) {
	usec = 0;
    }

    /*
     * TIP #233: Scale from virtual time to real-time for select/usleep.
................................................................................
    now = TclpGetUTimeMonotonic();
    if ((desired = (now + usec)) < now) { /* overflow */
	desired = 0x7FFFFFFFFFFFFFFFL;
    }

    while (1) {
	
	if (usec >= TCL_TMR_MIN_DELAY) {

	    struct timeval delay;



	    delay.tv_sec  = usec / 1000000;
	    delay.tv_usec = usec % 1000000;

	    (void) select(0, (SELECT_MASK *) 0, (SELECT_MASK *) 0,
		(SELECT_MASK *) 0, &delay);

	} else if (usec >= TCL_TMR_MIN_SLEEP) {


	    usleep((useconds_t)(usec - TCL_TMR_MIN_SLEEP));
	} else {
	    /* nanosleep has the same minimal sleep interval as usleep */
#if 0
	    struct timespec delay;



	    delay.tv_sec  = usec / 1000000;
	    delay.tv_nsec = (usec % 1000000) * 1000; /* usec to nsec */

	    nanosleep(&delay, NULL);




#endif
	}
	
	now = TclpGetUTimeMonotonic();

	if ((usec = (desired - now)) <= 0 /* or tolerance */) {







	    break;
	}
    }
}
 
/*
 *----------------------------------------------------------------------






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 *
 * Note: Adjusting of this values may increase NRT-capability, but also may
 * 	 increase CPU load (resp. busy waits on brief intervals).
 */

#ifndef TCL_TMR_MIN_DELAY
#   define TCL_TMR_MIN_DELAY 100
#   define TCL_TMR_MIN_USLEEP 50
#   define TCL_TMR_MIN_NSLEEP 1
#   define TCL_TMR_OVERHEAD 50
#endif

/*
 *----------------------------------------------------------------------
 *
 * TclpUSleep --
................................................................................
 *
 * Side effects:
 *	Time passes.
 *
 *----------------------------------------------------------------------
 */

static unsigned int tclMinDelay  = TCL_TMR_MIN_DELAY;
static unsigned int tclMinUSleep = TCL_TMR_MIN_USLEEP;
static unsigned int tclMinNSleep = TCL_TMR_MIN_NSLEEP;

void
TclpUSleep(
    Tcl_WideInt usec)	/* Time to sleep. */
{
    Tcl_WideInt now, desired;
    unsigned int *calibValue;

    if (usec < 0) {
	usec = 0;
    }

    /*
     * TIP #233: Scale from virtual time to real-time for select/usleep.
................................................................................
    now = TclpGetUTimeMonotonic();
    if ((desired = (now + usec)) < now) { /* overflow */
	desired = 0x7FFFFFFFFFFFFFFFL;
    }

    while (1) {
	
	if (usec >= tclMinDelay) {

	    struct timeval delay;

	    calibValue = &tclMinDelay;
	    usec -= (usec % tclMinDelay);
	    delay.tv_sec  = usec / 1000000;
	    delay.tv_usec = usec % 1000000;

	    (void) select(0, (SELECT_MASK *) 0, (SELECT_MASK *) 0,
		(SELECT_MASK *) 0, &delay);

	} else if (usec >= tclMinUSleep) {
	    calibValue = &tclMinUSleep;
	    usec -= (usec % tclMinUSleep);
	    usleep((useconds_t)usec);


	} else if (usec >= tclMinNSleep) {
	    struct timespec delay;

	    calibValue = &tclMinNSleep;
	    usec -= (usec % tclMinNSleep);
	    delay.tv_sec  = usec / 1000000;
	    delay.tv_nsec = (usec % 1000000) * 1000; /* usec to nsec */

	    nanosleep(&delay, NULL);
	} else {
	    calibValue = NULL;
#ifdef _POSIX_PRIORITY_SCHEDULING
	    sched_yield(); /* yield the processor (force context switch). */
#endif
	}
	
	now = TclpGetUTimeMonotonic();

	if ((usec = (desired - now)) <= 0 /* or tolerance */) {
	    /*
	     * Self calibration - sleep was too long, so adjust related value.
	     */
	    if (calibValue && (unsigned int)-usec > *calibValue) {
		*calibValue = (*calibValue + (unsigned int)-usec) / 2;
	    }
	    /* end of sleep */
	    break;
	}
    }
}
 
/*
 *----------------------------------------------------------------------