timing_test.cc

#define __STDC_FORMAT_MACROS

#include <sys/time.h>
#include <time.h>
#include <stdlib.h>
#include <sys/syscall.h>
#include <unistd.h>
#include <dlfcn.h>
#include <stdio.h>
#include <string.h>
#include <inttypes.h>

typedef int (*vgettime_t)(clockid_t, timespec *);

void describe_clock(const char *name, int id)
{
	struct timespec res;
	int ret = clock_getres(id, &res);
	if (ret < 0) {
		printf("  %d (%s)  [failed to query resolution]\n",
		       id, name);
	} else {
		printf("  %d (%s)  resolution = %" PRIu64 ".%09u\n",
		       id, name,
		       (uint64_t)res.tv_sec, (unsigned)res.tv_nsec);
	}
}

int main(int argc, char **argv)
{
	if (argc < 3) {
		printf("Usage: time <Miters> <mode> [POSIX clock id]\n");
		printf("\nClocks are:\n");
		describe_clock("CLOCK_REALTIME", CLOCK_REALTIME);
		describe_clock("CLOCK_MONOTONIC", CLOCK_MONOTONIC);
		describe_clock("CLOCK_REALTIME_COARSE", CLOCK_REALTIME_COARSE);
		describe_clock("CLOCK_MONOTONIC_COARSE", CLOCK_MONOTONIC_COARSE);
		return 1;
	}

	void *vdso = dlopen("linux-vdso.so.1", RTLD_LAZY | RTLD_LOCAL | RTLD_NOLOAD);
	if (!vdso)
		vdso = dlopen("linux-gate.so.1", RTLD_LAZY | RTLD_LOCAL | RTLD_NOLOAD);
	if (!vdso)
		printf("dlopen failed\n");;

	vgettime_t vgettime = (vgettime_t)dlsym(vdso, "__vdso_clock_gettime");
	if (!vgettime)
		printf("dlsym failed: %s", dlerror());

	size_t loops = (size_t)atol(argv[1]) * 1000000;
	clockid_t c = argc > 3 ? atoi(argv[3]) : 0;
	const char *mode = argv[2];

	timespec start;
	clock_gettime(CLOCK_MONOTONIC, &start);

        timespec t;
	if (!strcmp(mode, "clock_gettime")) {
	        for (size_t i = 0; i < loops; ++i)
        	        clock_gettime(c, &t);
	} else if (!strcmp(mode, "rdtsc")) {
	        for (size_t i = 0; i < loops; ++i) {
			unsigned int a, d;
			asm volatile ("rdtsc" : "=a" (a), "=d" (d));
		}
	} else if (!strcmp(mode, "lfence_rdtsc")) {
	        for (size_t i = 0; i < loops; ++i) {
			unsigned int a, d;
			asm volatile ("lfence;rdtsc" : "=a" (a), "=d" (d));
		}
	} else if (!strcmp(mode, "lfence_rdtsc_lfence")) {
	        for (size_t i = 0; i < loops; ++i) {
			unsigned int a, d;
			asm volatile ("");
			asm volatile ("lfence;rdtsc;lfence" : "=a" (a), "=d" (d));	
		}
	} else if (!strcmp(mode, "mfence_rdtsc_mfence")) {
	        for (size_t i = 0; i < loops; ++i) {
			unsigned int a, d;
			asm volatile ("mfence;rdtsc;mfence" : "=a" (a), "=d" (d));
		}
	} else if (!strcmp(mode, "rdtscp")) {
	        for (size_t i = 0; i < loops; ++i) {
			unsigned int a, c, d;
			asm volatile ("rdtscp" : "=a" (a), "=c" (c), "=d" (d));
		}
	} else if (!strcmp(mode, "gettimeofday")) {
		struct timeval tv;
	        for (size_t i = 0; i < loops; ++i)
			gettimeofday(&tv, 0);
	} else if (!strcmp(mode, "sys_clock_gettime")) {
	        for (size_t i = 0; i < loops; ++i)
        	        syscall(__NR_clock_gettime, c, &t);
	} else if (!strcmp(mode, "vclock_gettime")) {
	        for (size_t i = 0; i < loops; ++i)
        	        vgettime(c, &t);
	} else if (!strcmp(mode, "getpid")) {
	        for (size_t i = 0; i < loops; ++i)
			syscall(SYS_getpid);
	} else if (!strcmp(mode, "rdpmc")) {
		// Unlikely to work.
		unsigned int eax, edx;
		unsigned int ecx = 0;
	        for (size_t i = 0; i < loops; ++i)
			asm volatile ("rdpmc" : "=a" (eax), "=d" (edx) : "c" (ecx));
	} else {
		printf("Unknown mode %s\n", mode);
		return 1;
	}

	timespec end;
	clock_gettime(CLOCK_MONOTONIC, &end);
	unsigned long long duration = (end.tv_nsec - start.tv_nsec) + 1000000000ULL * (end.tv_sec - start.tv_sec);
	printf("%ld loops in %.5fs = %.2f nsec / loop\n",
	       (long)loops, float(duration) * 1e-9,
	       float(duration) / loops);
	return 0;
}