libtopo/timestamp.c

#include <stdint.h>
#include <immintrin.h>
#include <x86intrin.h>
#include <errno.h>
#include <sys/sysctl.h>

#include "topo.h"
#include "topop.h"

#define S2NS (1000000000UL)

static uint64_t
tsc2ns(uint64_t tsc, uint64_t tsc_freq)
{
	return (uint64_t)(
	    (double)tsc / (double)tsc_freq * S2NS);
}

int
topo_ts_init(struct topo_desc * desc, int verbose)
{
    int rc;

    size_t sz = sizeof(desc->tsc_freq);

	// init nm_tsc2ns
	if ((rc = sysctlbyname("machdep.tsc_freq", &desc->tsc_freq, &sz, NULL, 0)) < 0) {
		fprintf(stderr,"libtopo: failed to query tsc frequency via sysctl (%d)\n", errno);
	} else {
		if (verbose) {
			fprintf(stdout,"libtopo: tsc frequency = %lu\n", desc->tsc_freq);
		}
	}

    return rc;
}

uint64_t
topo_desc_uptime_ns(struct topo_desc * desc)
{
	unsigned int dummy;
	_mm_lfence();
	uint64_t tsc = __rdtscp(&dummy);
	_mm_lfence();
	return tsc2ns(tsc, desc->tsc_freq);
}