syscall execution time sampling test

syscallsample.c

#include <signal.h>
#include <stdio.h>
#include <stdlib.h>

#define NSAMPLES        64

struct sample {
        u_int64_t       pre;
        u_int64_t       post;
        u_int64_t       cycles;
} sample[NSAMPLES];

static inline u_int64_t
rdtsc(void)
{
        u_int32_t       lo, hi;

        __asm __volatile("rdtsc; movl %%eax, %0; movl %%edx, %1"
            : "=r" (lo), "=r" (hi) : : "eax", "edx");

        return ((u_int64_t)lo | ((u_int64_t)hi << 32));
}

u_int64_t
call_sample(struct sample *data, int count, void (*fn)(void))
{
        int             i;
        u_int64_t       total = 0;

        for (i = 0; i < count; i++) {
                data[i].pre = rdtsc();
                fn();
                data[i].post = rdtsc();
        }

        for (i = 0; i < count; i++) {
                total += data[i].cycles = data[i].post - data[i].pre;
                printf("sample %d: cycles:  %llu\n",
                    i, data[i].cycles);
        }

        return (total / count);
}

void
sample_kill(void)
{
        return (void)(kill(1, 0));
}

int
main(int argc, char **argv)
{
        u_int64_t       avg;

        printf("sampling: kill(1, 0)\n");
        avg = call_sample(sample, NSAMPLES, sample_kill);
        printf("average: %llu\n", avg);

        return (0);
}