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spinloop timing that seeks to directly match apple speed
This commit is contained in:
Aaron Culliney
parent
980bcc627d
commit
1f9a1778b9
98
src/timing.c
98
src/timing.c
@ -24,12 +24,11 @@
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#define CALIBRATE_HZ 100
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static unsigned long CPU_TARGET_HZ = APPLE2_HZ; // target clock speed
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static unsigned long CALIBRATE_INTERVAL = NANOSECONDS / CALIBRATE_HZ; // calibration interval for drifting
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static unsigned long CALIBRATE_INTERVAL_NSECS = NANOSECONDS / CALIBRATE_HZ; // calibration interval for drifting
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static float CYCLE_NSECS = NANOSECONDS / (float)APPLE2_HZ; // nanosecs per cycle
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static struct timespec ti;
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static int spinloop_count=0; // spin loop counter
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static float spin_ratio=0.0;
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// -----------------------------------------------------------------------------
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@ -52,10 +51,6 @@ static inline struct timespec timespec_diff(struct timespec start, struct timesp
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return t;
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}
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static inline long timespec_nsecs(struct timespec t) {
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return t.tv_sec*NANOSECONDS + t.tv_nsec;
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}
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// spin loop to throttle to target CPU Hz
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static inline void _spin_loop(unsigned long c)
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{
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@ -75,7 +70,7 @@ static void _determine_initial_spinloop_counter()
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unsigned long avg_spin_nsecs = 0;
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unsigned int const samples = 5;
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unsigned int i=0;
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spinloop_count = 500000000;
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unsigned int spinloop_count = 250000000;
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do
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{
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clock_gettime(CLOCK_MONOTONIC, &s0);
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@ -85,24 +80,25 @@ static void _determine_initial_spinloop_counter()
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if (deltat.tv_sec > 0)
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{
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printf("oops long wait (>= %lu sec) adjusting loop count (%d -> %d)\n", deltat.tv_sec, spinloop_count, spinloop_count>>1);
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LOG("oops long wait (>= %lu sec) adjusting loop count (%d -> %d)", deltat.tv_sec, spinloop_count, spinloop_count>>1);
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spinloop_count >>= 1;
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i = 0;
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avg_spin_nsecs = 0;
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continue;
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}
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printf("spinloop = %lu nsec\n", deltat.tv_nsec);
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LOG("spinloop = %lu nsec", deltat.tv_nsec);
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avg_spin_nsecs += deltat.tv_nsec;
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++i;
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} while (i<samples);
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avg_spin_nsecs = (avg_spin_nsecs / samples);
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printf("average = %lu nsec\n", avg_spin_nsecs);
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LOG("average = %lu nsec , spinloop_count = %u , samples = %u", avg_spin_nsecs, spinloop_count, samples);
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spinloop_count = CYCLE_NSECS * spinloop_count / avg_spin_nsecs;
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// counter for 1 nsec
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spin_ratio = avg_spin_nsecs / ((float)spinloop_count);
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printf("counter for a single %fns cycle = %d\n", CYCLE_NSECS, spinloop_count);
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LOG("%fns cycle spins for average %f", CYCLE_NSECS, spin_ratio);
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}
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void timing_initialize() {
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@ -118,32 +114,6 @@ void timing_set_cpu_scale(unsigned int scale)
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// ...
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}
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/*
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* Calibrate emulator clock to real clock ...
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*
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* NOTE: these calculations could overflow if emulator speed is severely dampened back...
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*/
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static int _calibrate_clock (long drift_interval_nsecs)
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{
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return 0;
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// HACK FIXME : this is broken, plz debug, kthxbye!
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struct timespec tj, deltat;
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clock_gettime(CLOCK_MONOTONIC, &tj);
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deltat = timespec_diff(ti, tj);
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ti=tj;
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long real_nsecs = NANOSECONDS * deltat.tv_sec + deltat.tv_nsec;
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int drift_nsecs = (int)(drift_interval_nsecs - real_nsecs); // +/- nsec drift
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int drift_count = (int)(drift_nsecs * (spinloop_count / CYCLE_NSECS) ); // +/- count drift
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// adjust spinloop_count ...
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spinloop_count += drift_count / CALIBRATE_INTERVAL;
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// ideally we should return a sub-interval here ...
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return 0;
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}
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/*
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* Throttles 6502 CPU down to the target CPU frequency (default is speed of original Apple //e).
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*
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@ -151,32 +121,44 @@ static int _calibrate_clock (long drift_interval_nsecs)
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*/
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void timing_throttle()
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{
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static float drift_interval=0.0;
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static int spinloop_adjust=0;
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struct timespec tj, deltat;
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clock_gettime(CLOCK_MONOTONIC, &tj);
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deltat = timespec_diff(ti, tj);
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ti=tj;
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static time_t severe_lag=0;
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if (deltat.tv_sec != 0)
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{
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// severely lagging...
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if (severe_lag < time(NULL))
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{
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severe_lag = time(NULL)+2;
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LOG("Severe lag detected...");
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}
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return;
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}
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uint8_t opcycles = cpu65__opcycles[cpu65_debug.opcode] + cpu65_debug.opcycles;
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uint8_t c=0;
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if (spinloop_adjust < 0)
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unsigned long opcycles_nsecs = opcycles * (CYCLE_NSECS/2);
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if (deltat.tv_nsec >= opcycles_nsecs)
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{
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c=-1;
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++spinloop_adjust;
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}
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else if (spinloop_adjust > 0)
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{
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c=1;
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--spinloop_adjust;
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// lagging
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return;
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}
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// spin for the desired/estimated number of nsecs
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_spin_loop(opcycles * (spinloop_count+c));
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unsigned long diff_nsec = opcycles_nsecs - deltat.tv_nsec;
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drift_interval += opcycles*CYCLE_NSECS;
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if (drift_interval > CALIBRATE_INTERVAL)
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static time_t sample_time=0;
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if (sample_time < time(NULL))
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{
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// perform calibration
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spinloop_adjust = _calibrate_clock((long)drift_interval);
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drift_interval = 0.0;
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sample_time = time(NULL)+1;
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//LOG("sample diff_nsec : %lu", diff_nsec);
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}
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unsigned long spin_count = spin_ratio * diff_nsec;
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// spin for the rest of the interval ...
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_spin_loop(spin_count);
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}
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