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Bug 64165: Fix RDTSC calibration #65

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merged 1 commit into from Dec 24, 2013
Merged

Bug 64165: Fix RDTSC calibration #65

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21 changes: 11 additions & 10 deletions extension/xhprof.c
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Expand Up @@ -1360,23 +1360,24 @@ static double get_cpu_frequency() {
struct timeval end;
uint64 tsc_start;
uint64 tsc_end;
volatile int i;

if (gettimeofday(&start, 0)) {
perror("gettimeofday");
return 0.0;
}

tsc_start = cycle_timer();

/* Sleep for 5 miliseconds. Comparaing with gettimeofday's few microseconds
* execution time, this should be enough. */
usleep(5000);
if (gettimeofday(&end, 0)) {
perror("gettimeofday");
return 0.0;
}
tsc_start = cycle_timer();

tsc_end = cycle_timer();
/* Busy loop for 5 miliseconds. */
do {
for (i = 0; i < 1000000; i++);
if (gettimeofday(&end, 0)) {
perror("gettimeofday");
return 0.0;
}
tsc_end = cycle_timer();
} while (get_us_interval(&start, &end) < 5000);

return (tsc_end - tsc_start) * 1.0 / (get_us_interval(&start, &end));
}
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