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spinloop timing that seeks to directly match apple speed

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This commit is contained in:
Aaron Culliney 2013-07-25 22:58:31 -07:00
parent 980bcc627d
commit 1f9a1778b9
1 changed files with 42 additions and 60 deletions
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102
src/timing.c
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@ -23,13 +23,12 @@
#define CALIBRATE_HZ 100
static unsigned long CPU_TARGET_HZ = APPLE2_HZ; // target clock speed
static unsigned long CALIBRATE_INTERVAL = NANOSECONDS / CALIBRATE_HZ; // calibration interval for drifting
static float CYCLE_NSECS = NANOSECONDS / (float)APPLE2_HZ; // nanosecs per cycle
static unsigned long CPU_TARGET_HZ = APPLE2_HZ; // target clock speed
static unsigned long CALIBRATE_INTERVAL_NSECS = NANOSECONDS / CALIBRATE_HZ; // calibration interval for drifting
static float CYCLE_NSECS = NANOSECONDS / (float)APPLE2_HZ; // nanosecs per cycle
static struct timespec ti;
static int spinloop_count=0; // spin loop counter
static float spin_ratio=0.0;
// -----------------------------------------------------------------------------
@ -52,10 +51,6 @@ static inline struct timespec timespec_diff(struct timespec start, struct timesp
return t;
}
static inline long timespec_nsecs(struct timespec t) {
return t.tv_sec*NANOSECONDS + t.tv_nsec;
}
// spin loop to throttle to target CPU Hz
static inline void _spin_loop(unsigned long c)
{
@ -75,7 +70,7 @@ static void _determine_initial_spinloop_counter()
unsigned long avg_spin_nsecs = 0;
unsigned int const samples = 5;
unsigned int i=0;
spinloop_count = 500000000;
unsigned int spinloop_count = 250000000;
do
{
clock_gettime(CLOCK_MONOTONIC, &s0);
@ -85,24 +80,25 @@ static void _determine_initial_spinloop_counter()
if (deltat.tv_sec > 0)
{
printf("oops long wait (>= %lu sec) adjusting loop count (%d -> %d)\n", deltat.tv_sec, spinloop_count, spinloop_count>>1);
LOG("oops long wait (>= %lu sec) adjusting loop count (%d -> %d)", deltat.tv_sec, spinloop_count, spinloop_count>>1);
spinloop_count >>= 1;
i = 0;
avg_spin_nsecs = 0;
continue;
}
printf("spinloop = %lu nsec\n", deltat.tv_nsec);
LOG("spinloop = %lu nsec", deltat.tv_nsec);
avg_spin_nsecs += deltat.tv_nsec;
++i;
} while (i<samples);
avg_spin_nsecs = (avg_spin_nsecs / samples);
printf("average = %lu nsec\n", avg_spin_nsecs);
LOG("average = %lu nsec , spinloop_count = %u , samples = %u", avg_spin_nsecs, spinloop_count, samples);
spinloop_count = CYCLE_NSECS * spinloop_count / avg_spin_nsecs;
// counter for 1 nsec
spin_ratio = avg_spin_nsecs / ((float)spinloop_count);
printf("counter for a single %fns cycle = %d\n", CYCLE_NSECS, spinloop_count);
LOG("%fns cycle spins for average %f", CYCLE_NSECS, spin_ratio);
}
void timing_initialize() {
@ -118,32 +114,6 @@ void timing_set_cpu_scale(unsigned int scale)
// ...
}
/*
* Calibrate emulator clock to real clock ...
*
* NOTE: these calculations could overflow if emulator speed is severely dampened back...
*/
static int _calibrate_clock (long drift_interval_nsecs)
{
return 0;
// HACK FIXME : this is broken, plz debug, kthxbye!
struct timespec tj, deltat;
clock_gettime(CLOCK_MONOTONIC, &tj);
deltat = timespec_diff(ti, tj);
ti=tj;
long real_nsecs = NANOSECONDS * deltat.tv_sec + deltat.tv_nsec;
int drift_nsecs = (int)(drift_interval_nsecs - real_nsecs); // +/- nsec drift
int drift_count = (int)(drift_nsecs * (spinloop_count / CYCLE_NSECS) ); // +/- count drift
// adjust spinloop_count ...
spinloop_count += drift_count / CALIBRATE_INTERVAL;
// ideally we should return a sub-interval here ...
return 0;
}
/*
* Throttles 6502 CPU down to the target CPU frequency (default is speed of original Apple //e).
*
@ -151,32 +121,44 @@ static int _calibrate_clock (long drift_interval_nsecs)
*/
void timing_throttle()
{
static float drift_interval=0.0;
static int spinloop_adjust=0;
struct timespec tj, deltat;
clock_gettime(CLOCK_MONOTONIC, &tj);
deltat = timespec_diff(ti, tj);
ti=tj;
static time_t severe_lag=0;
if (deltat.tv_sec != 0)
{
// severely lagging...
if (severe_lag < time(NULL))
{
severe_lag = time(NULL)+2;
LOG("Severe lag detected...");
}
return;
}
uint8_t opcycles = cpu65__opcycles[cpu65_debug.opcode] + cpu65_debug.opcycles;
uint8_t c=0;
if (spinloop_adjust < 0)
unsigned long opcycles_nsecs = opcycles * (CYCLE_NSECS/2);
if (deltat.tv_nsec >= opcycles_nsecs)
{
c=-1;
++spinloop_adjust;
}
else if (spinloop_adjust > 0)
{
c=1;
--spinloop_adjust;
// lagging
return;
}
// spin for the desired/estimated number of nsecs
_spin_loop(opcycles * (spinloop_count+c));
unsigned long diff_nsec = opcycles_nsecs - deltat.tv_nsec;
drift_interval += opcycles*CYCLE_NSECS;
if (drift_interval > CALIBRATE_INTERVAL)
static time_t sample_time=0;
if (sample_time < time(NULL))
{
// perform calibration
spinloop_adjust = _calibrate_clock((long)drift_interval);
drift_interval = 0.0;
sample_time = time(NULL)+1;
//LOG("sample diff_nsec : %lu", diff_nsec);
}
unsigned long spin_count = spin_ratio * diff_nsec;
// spin for the rest of the interval ...
_spin_loop(spin_count);
}