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TIMER: Be less aggressive to disable throttling after initial calibration

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- removed a somwhat unlikely but possible division-by-zero
- in case the initial throttling calibration measures a slower cps rate than
   the desired cps rate, check whether the measured rate is well below the
   measured peak rate. If so, distrust the measured rate and instead use
   half the peak rate as measured cps rate.
   Otherwise (so measured cps is in the same ballpark as measured peak rate)
   disable throttling

As initially reported in #815
This commit is contained in:
Heinz-Bernd Eggenstein 2021-10-23 13:50:48 -07:00 • committed by Mark Pizzolato
parent 1e4401fd84
commit 525215b07e
1 changed files with 25 additions and 8 deletions
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33
sim_timer.c
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@ -1994,16 +1994,33 @@ switch (sim_throt_state) {
d_cps = (double) sim_throt_val * 1000.0;
else
d_cps = (sim_throt_peak_cps * sim_throt_val) / 100.0;
if (d_cps > a_cps) {
if (d_cps >= a_cps) {
/* the initial throttling calibration measures a slower cps rate than the desired cps rate, */
sim_debug (DBG_THR, &sim_timer_dev, "sim_throt_svc() CPU too slow. Values a_cps = %f, d_cps = %f\n",
a_cps, d_cps);
sim_throt_state = SIM_THROT_STATE_INIT;
sim_printf ("*********** WARNING ***********\n");
sim_printf ("Host CPU is too slow to simulate %s %s per second\n", sim_fmt_numeric(d_cps), sim_vm_interval_units);
sim_printf ("Host CPU can only simulate %s %s per second\n", sim_fmt_numeric(sim_throt_peak_cps), sim_vm_interval_units);
sim_printf ("Throttling disabled.\n");
sim_set_throt (0, NULL);
return SCPE_OK;
/* if the measured rate is well below the measured peak rate? */
if (sim_throt_peak_cps >= (2.0 * d_cps)) {
/* distrust the measured rate and instead use half the peak rate as measured
cps rate. */
sim_printf ("*********** WARNING ***********\n");
sim_printf ("Host CPU could be too slow to simulate %s %s per second\n", sim_fmt_numeric(d_cps), sim_vm_interval_units);
sim_printf ("Host CPU did only simulate %s %s per second\n", sim_fmt_numeric(a_cps), sim_vm_interval_units);
sim_printf ("But peak rate was: %s %s per second\n", sim_fmt_numeric(sim_throt_peak_cps), sim_vm_interval_units);
a_cps = (sim_throt_peak_cps / 2.0) + 1.0;
sim_printf ("Assuming rate: %s %s per second\n", sim_fmt_numeric(a_cps), sim_vm_interval_units);
}
else {
sim_throt_state = SIM_THROT_STATE_INIT;
sim_printf ("*********** WARNING ***********\n");
sim_printf ("Host CPU is too slow to simulate %s %s per second\n", sim_fmt_numeric(d_cps), sim_vm_interval_units);
sim_printf ("Host CPU did only simulate %s %s per second\n", sim_fmt_numeric(a_cps), sim_vm_interval_units);
sim_printf ("Peak rate: %s %s per second\n", sim_fmt_numeric(sim_throt_peak_cps), sim_vm_interval_units);
sim_printf ("Throttling disabled.\n");
sim_set_throt (0, NULL);
return SCPE_OK;
}
}
while (1) {
sim_throt_wait = (int32) /* cycles between sleeps */