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em.c: add a small benchmark loop to set the initial value of instpermsec

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to a reasonable value.  This avoids clock anomolies during startup.
This commit is contained in:
Jim Wilcoxson 2020-04-19 01:14:15 +00:00
parent 4a1bfefa4a
commit b3cada1dbf
1 changed files with 31 additions and 1 deletions
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32
em.c
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@ -4412,7 +4412,10 @@ int main (int argc, char **argv) {
NOTE: if instpermsec is off by more than a factor of 2, it causes
some minor clock skew problems during the first few seconds of
system boot. There is debug code in emdev.h/devcp to see this. */
system boot. There is debug code in emdev.h/devcp to see this.
To remedy, a small benchmark is run after initialization to set a
"close" value based on empirical testing, then the clock process
adjusts it periodically. */
gv.intvec = -1;
gv.instcount = 0;
@ -4706,6 +4709,33 @@ int main (int argc, char **argv) {
}
bzero(MEM, 64*1024*2); /* zero first 64K words */
/* run a short benchmark to help determine initial MIPS rating. For
a system with an actual Prime MIPS rating of 58, this benchmark
returns numbers around 160, so divide by 3-ish with -DFAST or
7-ish without -DFAST*/
{
#define BENCHINST 10000000
#ifdef FAST
#define BENCHFACTOR 2.9
#else
#define BENCHFACTOR 7.0
#endif
struct timeval start_tv, tv;
int elapsedms;
if (gettimeofday(&start_tv, NULL) != 0)
fatal("em: gettimeofday failed");
for (templ=0; templ < BENCHINST; templ++) {
add16(1, 2, 3, 0);
}
if (gettimeofday(&tv, NULL) != 0)
fatal("em: gettimeofday failed");
elapsedms = (tv.tv_sec-start_tv.tv_sec)*1000.0 + (tv.tv_usec-start_tv.tv_usec)/1000.0;
gv.instpermsec = BENCHINST * 1.0 / elapsedms / BENCHFACTOR;
printf("=== %d Prime MIPS ===\n", gv.instpermsec / 1000);
}
/* if no maps were specified on the command line, look for ring0.map and
ring3.map in the current directory and read them */