/*
 * mutex3.c
 *
 * $DragonFly: src/test/sysperf/mutex3.c,v 1.1 2006/05/18 02:22:46 dillon Exp $
 */

#include "blib.h"

#include <sys/types.h>
#include <machine/atomic.h>
#include <machine/cpufunc.h>

int *mtx;
int refcnt;

static void
spin_lock_contested(void)
{
        int i;
        int j;

        j = 1;
        while (atomic_swap_int(mtx, 1) != 0) {
                for (i = 0; i < j; ++i)
                        __asm __volatile("pause"::);
                j <<= 1;
        }
}

static __inline void
spin_lock(void)
{
        if (refcnt == 1) {
                if (*mtx == 0)
                        *mtx = 1;
                else
                        spin_lock_contested();
        } else if (atomic_swap_int(mtx, 1) != 0) {
                spin_lock_contested();
        }
}

static __inline void
spin_unlock(void)
{
        cpu_sfence();
        *mtx = 0;
}

int
main(int ac, char **av)
{
    long long count = 0;
    long long max;
    int j;
    int *counter;
    pid_t pid;

    printf("Test simple locked bus cycle mutex latency\n");
    printf("auto-forks two processes for the test with shared memory\n");
    printf("This test is only useful on a SMP box\n");

    start_timing();
    mtx = mmap(NULL, 4096, PROT_READ|PROT_WRITE, MAP_SHARED|MAP_ANON, -1, 0);
    counter = mtx + 64;
    while (stop_timing(0, NULL) == 0) {
        for (j = 0; j < 100; ++j) {
            spin_lock();
            spin_unlock();
        }
        count += 100;
    }
    max = count;
    *mtx = 0;

    refcnt = 1;
    start_timing();
    for (count = 0; count < max; count += 100) {
        for (j = 0; j < 100; ++j) {
            spin_lock();
            spin_unlock();      /* release */
            ++counter[64];
        }
    }
    stop_timing(count, "complex_mtx(uncontested/1cpu)");
    refcnt = 2;

    if ((pid = fork()) == 0) {
        for (;;) {
            for (j = 0; j < 100; ++j) {
                spin_lock();
                spin_unlock();  /* release */
                ++counter[128];
            }
        }
    } else {
        start_timing();
        for (count = 0; count < max; count += 100) {
            for (j = 0; j < 100; ++j) {
                spin_lock();
                spin_unlock();  /* release */
                ++counter[64];
            }
        }
        stop_timing(count, "complex_mtx");
        printf("proc1=%d proc2=%d\n", counter[64], counter[128]);
        kill(pid, 9);
    }
    return(0);
}